Faults by symptom

You arrive here with a symptom, not with a chip name. This page turns the wiki's Common faults tables inside out: pick what the machine does, and it lists every page that documents it, with that page's own probable cause. 959 entries, gathered from 206 pages.

What this page is, and is not

Every line quotes its page — symptom, probable cause, next step. Nothing is reworded and nothing is inferred: the page of origin remains the reference, and the link takes you to its full context, which a table cannot hold. If your symptom is not listed here, it is not documented in the wiki — not that it does not exist.

Motion & force feedback (7)

Symptom	Probable cause	Next step	Page
Cabinet motion dead	motion board / actuators	Mechanical diagnosis	Namco System 22 / Super System 22
Cabinet motion dead	motion board / actuators	Mechanical diagnosis	Namco System 23 (Gorgon / Super System 23)
Cabinet motion dead	motion board / actuators	Mechanical diagnosis	Sega X-Board
Cabinet motion dead	motion board / actuators	Mechanical diagnosis	Sega Y-Board
Cabinet motion dead	motion board / actuators	Mechanical diagnosis	Taito Z System
Force feedback dead (Hard Drivin')	force-feedback board / motor	Mechanical + board diagnosis	Atari — arcade (System 1/2, Hard Drivin')
No force feedback (cabinet)	motion board / motors	Cabinet mechanical diagnosis	Sega "Super Scaler" (Hang-On / Space Harrier / OutRun)

Sound (159)

Symptom	Probable cause	Next step	Page
Absent / noisy sound	S-SMP / APU	Sound-stage diagnosis	Super Nintendo / Super Famicom (SNES / SFC)
Buzz / stray noise	Sound stage / caps	Targeted recap	GCE / MB Vectrex
Corrosion / dead sound / "simasimac"	SMD logic-board caps (SE/30)	Recap + clean	Apple Macintosh compact (128K → SE/30)
Corrosion / degraded sound	SMD capacitors	Recap	Sega 32X
Corrosion / degraded sound-video	Capacitors	Targeted recap	Sega Saturn
Corrosion / sound-video	Capacitors	Recap	3DO Interactive Multiplayer
Crunchy / crackling audio	Power switch, headphone jack, caps	Clean the power switch; pipe cleaner + IPA in the headphone jack; full recap — especially C32 (GBC)	Game Boy / Game Boy Color
Dead sound / crashes (A600/1200)	leaked SMD caps	Recap + cleaning	Commodore Amiga
Degraded picture/sound	ageing capacitors	Targeted recap of the affected stage	Amstrad GX4000
Degraded picture/sound	tired caps	Targeted recap	Sega Mark III
Degraded sound/video (Model 2)	Leaking SMD caps	Recap (see below)	Sega Mega Drive / Genesis
Degraded sound/video, corrosion	Capacitors (electrolytics)	Targeted recap	NEC PC-FX
Degraded sound/video, corrosion	Capacitors	Targeted recap	Philips CD-i
Degraded sound/video, corrosion	Leaking capacitors (incl. SMD)	Recap — ⚠️ on the Model 1, do it even with no visible leakage; remember the sub board near the regulator and, on JVC drives, the drive controller board	Sega Mega-CD / Sega CD
Degraded sound/video, corrosion	Capacitors (electrolytics)	Targeted recap	SNK Neo Geo CD
Degraded sound/video, corrosion (CoreGrafx/Duo)	Leaking SMD capacitors	Recap	NEC PC Engine / TurboGrafx-16
Degraded video/sound	caps / customs	Recap, substitution	Sharp X68000
Distorted / weak / no sound (20-EZV)	audio board (bipolar caps, TR373 / TR374); JB/JC reversed → burnt resistors	Audio recap + transistors; check the JB/JC connector orientation	Repair: Sanyo 20-EZ monitor
FM silent	FM add-on / YM2413	Check connector, test the chip	Sega Mark III
Hum / noise	missing earth, no common ground	Check earth + common ground	Power supplies in cabinets
Incomplete sound	PSG / (FM)	Sound-stage diagnosis	Sega Master System (Mark III)
Keyboard Component silent	its M6502 or its 7.15909 MHz crystal	A second system in its own right	Mattel Intellivision
Loss of a sound channel	YM or mixing stage	Probe diagnosis	Sega Mega Drive / Genesis
Loud whining noise	CleanAmp installed (notably with LEDs set to white on a button LED kit)	Remove the CleanAmp	Game Boy / Game Boy Color
Mute voice	TMS5220 (speech)	Sound-stage diagnosis	Atari — arcade (System 1/2, Hard Drivin')
Mute voice (Crazy Climber)	voice circuit / DAC	Sound-stage diagnosis	Nichibutsu (Crazy Climber, Moon Cresta, Terra Cresta)
Mute voice (Q*bert)	speech board	Speech-board diagnosis	Gottlieb (Qbert, Reactor, Mad Planets)
Mute voice / partial sound	VLM5030 / PSG	Sound-stage diagnosis	Konami Gradius / Nemesis / Twin16 (shmups)
No / noisy sound	SCSP (like the Saturn)	Sound-stage diagnosis	Sega ST-V (Titan Video)
No / partial sound	C140 (PCM) or YM2151 (FM) / sound 6809	Sound-stage diagnosis	Namco System 2
No / partial sound	sound 68000 / MultiPCM (315-5560) / YM3438	Sound-stage diagnosis	Sega Model 1
No / weak sound	+12 V (amp) or −5 V (analog)	Measure 12 V and −5 V	Power supplies in cabinets
No / wrong sound	Namco WSG / amp	Sound-stage diagnosis	Namco — classic hardware (Pac-Man / Galaga / Dig Dug / Xevious)
No digital sound	AY-3-8910A or MSM5205	Stages separate from the CEM3394	Bally / Sente SAC-1
No effects, music fine	OKI M6295	⚠️ its clock is not verified in MAME	Gaelco
No effects, music fine	one of the two OKI M6295s	Two separate chips, 4 MHz each	NMK 16-bit (NMK / UPL)
No effects, music fine	OKI M6295	The M6295 and the PIC are two separate stages	Playmark
No FM music	YM2203	Independent of the OKIs	NMK 16-bit (NMK / UPL)
No FM sound	YM2413 / MSX-MUSIC	Check the FM add-on	MSX (MSX / MSX2 / MSX2+ / turbo R)
No image but sound OK	Chassis / HV / monitor connectors	Chassis diagnosis	Sega Astro City
No music	SM64 (YM3812 clone)	YM3812 documentation applies	Deniam
No music	YM2413 (3.579545 MHz)	A stage separate from the other sound chips	Dynax
No music	YM3438 / SN76489	FM/PSG-stage diagnosis	Sega System C / C-2
No music	YM2151 or its 3.579545 MHz crystal	3.58 MHz is the classic NTSC colour crystal	Technos Japan
No music / sound	Z80 / YM2151 / SegaPCM	Sound-stage diagnosis	Sega "Super Scaler" (Hang-On / Space Harrier / OutRun)
No music on Speed Ball	YM3812 or the second Z80	This board has a dedicated sound CPU	Tecfri
No music, effects fine	YM3812 or the sound 6809	The two stages are separate on the first generation	Gaelco
No music, speech fine	one of the AY-3-8910s	Several of them: one dead channel tells them apart	Zaccaria
No PCM (voices/samples)	RF5C68 or its RAM	The FM stage can be fine while the PCM is silent	Sega System 18
No picture, sound fine	STIC	Custom chip with no replacement	Mattel Intellivision
No picture, sound fine	video stage	The sound/game separation makes the diagnosis clean	Eolith
No sound	the ASIC	⚠️ nothing to replace: the sound is integrated	Bit Corporation Gamate
No sound	μPD1771C or its 6 MHz crystal	A crystal separate from the CPU's	Epoch Super Cassette Vision
No sound	AY-3-8914	An AY-3-8910 variant, harder to source	Mattel Intellivision
No sound	buzzer or its joint	Independent of the display	Nintendo Game & Watch
No sound	Capacitors (sound board)	Recap	Sega Game Gear
No sound	sound card / IRQ/DMA	Check the Sound Blaster (jumpers/SET BLASTER)	IBM PC & compatibles (DOS gaming)
No sound	AY-3-8910	⚠️ MAME describes it as the Synthesizer PSG-01 add-on, yet instantiates it unconditionally and routes both joysticks through it. Whether the base machine is silent remains unverifiable. And MAME notes its own sound is "strange, volume often low to non-existent": do not use it to judge	Sanyo PHC-25
No sound	AY-3-8910 (I030)	Expected at 2 MHz	Tatung Einstein
No sound	Z80, YM2203/YM2413, or the ALPHA-VOICE88	Three separate stages	Alpha Denshi / ADK
No sound	Jerry custom (Jaguar)	Same remark	Atari Cojag
No sound	YMZ280B / OKI	Sound-stage diagnosis	Cave (68000 hardware)
No sound	sound Z80/6502 / YM / OKI	Sound-stage diagnosis	Data East (DECO Cassette, DECO 8/16/32)
No sound	YMZ280B or its 14 MHz clock	On the RAM/sound/I/O board, not the CPU board	Data East MLC
No sound	8032, QS1000, or the serial link between them	Three separate points — tell them apart before desoldering	Eolith
No sound	440 DAC / circuits	Sound-stage diagnosis	Exidy (Venture, Crossbow, Mouse Trap)
No sound	sound board	Sound-stage diagnosis	Gottlieb (Qbert, Reactor, Mad Planets)
No sound	OKI M6295, YM3812 or ICS2115	The sound stage varies by board	IGS011 (blitter hardware)
No sound	YMZ774-S	Independent stage	IGS PGM2
No sound	OKI M6295 (8-bit) / ES5506 (32-bit)	Sound-stage diagnosis	Incredible Technologies (Golden Tee)
No sound	Z80, YMF271, or the two-register link	Three points, not one	Jaleco Mega System 32
No sound	YMZ280B or its ADPCM	Stage independent of the video	Konami Firebeat
No sound	K054539 / sound 68000	Sound-stage diagnosis	Konami GX (System GX)
No sound	RF5C400, or the audio hard disk	The audio does not come from ROM	Konami Twinkle
No sound	SSIO board	A stage separate from the main board	Bally / Midway MCR
No sound	DCS (ADSP-2105) or Williams ADPCM	Sound-board diagnosis	Midway — Y-Unit, Wolf-Unit, V-Unit, Seattle, Zeus
No sound	C352 or its 24.576 MHz clock	Namco custom — no common replacement	Namco ND-1
No sound	SPU / customs	Sound-stage diagnosis	Namco System 10
No sound	sound customs	Sound-stage diagnosis	Namco System 21 "Polygonizer"
No sound	AICA (ARM7)	Sound-stage diagnosis	Sammy Atomiswave
No sound	SN76489 (/ FM)	Sound-stage diagnosis	Sega System E
No sound	sound Z80 / SN76489 (/ YM2151)	Sound-stage diagnosis	Sega System 1 / System 2
No sound	Z80 / YM2151	Sound-stage diagnosis	Sega System 16
No sound	MultiPCM (+ sound V60 / YM3438)	Sound-stage diagnosis	Sega System 32
No sound	discrete sound circuits	Sound-stage diagnosis	Sega / Gremlin VIC Dual
No sound	Z80 / YM2151 / SegaPCM	Sound-stage diagnosis	Sega X-Board
No sound	Z80 / YM2151 / SegaPCM	Sound-stage diagnosis	Sega Y-Board
No sound	X1-010 — or the OKI M6295, board depending	Check which of the two is fitted first	Seta
No sound	amp / PSG / SN76489	Sound-stage diagnosis	Taito — classics (Space Invaders, Qix, Bubble Bobble…)
No sound	Taito Zoom or the FC board's MN1020012A	⚠️ five games do not use Zoom — check which one is fitted	Taito G-NET
No sound	MC68EC000 or the ES5505	Two separate stages	Taito JC System
No sound	one of the AY-3-89xx	Two of them at different frequencies on Hole Land	Tecfri
No sound	AY / SN76489	Sound-stage diagnosis	Universal (Mr. Do!, Space Panic, Lady Bug)
No sound (MK1 T-unit)	Williams ADPCM board (6809/YM2151/OKI)	Sound-stage diagnosis	Midway T-Unit (Mortal Kombat II, NBA Jam…)
No sound (MK2/NBA Jam)	DCS stage (ADSP-2105)	DCS board diagnosis	Midway T-Unit (Mortal Kombat II, NBA Jam…)
No sound / dead keys	POKEY	Replace the POKEY	Atari 8-bit (400 / 800 / XL / XE)
No sound / flaky power	Capacitors	Recap	Atari Lynx
No sound / mono sound	Z80 / QSound / stereo wiring	Sound-stage diagnosis	Capcom CP System II (CPS-2)
No sound / mute voice	PSG / VLM5030 (speech)	Sound-stage diagnosis	Konami — classics (Frogger, Scramble, Time Pilot, Gyruss)
No sound / no CD boot	Leaked capacitors + traces	Recap + trace repair	PC Engine CD-ROM² / Duo
No sound / partial sound	YM2151 / MSM6295 / Z80	Sound-stage diagnosis (like CPS-1)	Capcom CPS Changer
No sound / partial sound	YM2151 / MSM6295 / Z80 (or QSound)	Sound-stage diagnosis	Capcom CP System (CPS-1)
No sound / weak sound	Capacitors (audio), speaker	Recap; check speaker	Game Boy / Game Boy Color
No sound / wrong sound	SID	Replace SID (correct voltage)	Commodore 64 Games System (C64GS)
No sound / wrong sound	SID	Replace SID (correct voltage)	Commodore 64
No sound at all	Z80 or NMK004, board depending	Establish which is fitted before probing	NMK 16-bit (NMK / UPL)
No sound at all	PIC16C57 or its 12 MHz clock	The PIC is a CPU in its own right, not a simple generator	Playmark
No sound on headphones	stereo audio DMA channel	The speaker is mono: test both	Watara Supervision
No sound, or wrong sound	machine-specific sound circuit	⚠️ see the caveat below	Emerson Arcadia 2001
No sound, or wrong sound	sound stage	⚠️ every machine carries "imperfect sound" in MAME (all nine)	Micronique Hector
No sound, Z80 appears stalled	YM2610 — it carries the interrupts	Do not condemn the Z80 first	Video System
No speech	Intellivoice module or its 3.12 MHz crystal	A crystal separate from the console's	Mattel Intellivision
No speech	Votrax SC01 or its driver	⚠️ its clock varies normally — see the box	Bally / Midway Astrocade
No speech	TMS5100	Speech-board diagnosis	Cinematronics (vector)
No speech (SFX ok)	speech board	Speech-board diagnosis	Sega G80 (raster & vector)
No speech (SFX OK)	CVSD HC55516 stage	Sound board diagnosis	Williams 6809 (Defender, Robotron, Joust…)
No speech, rest of the sound fine	TMS5220 or the 6802 driving it	Stage independent of the AY-3-8910s	Zaccaria
No streamed music	dead DSB board (68000 + MPEG)	DSB diagnosis (MPEG-music games: Daytona, Sega Rally)	Sega Model 2
No streamed music	DSB board (68000 + MPEG)	DSB diagnosis	Sega Model 3
No voices / samples	MSM5205 or OKI M6295, board depending	Check which is fitted	Dynax
No/partial sound	sound Z80 / YM2203	Sound-stage diagnosis	Capcom — pre-CPS classics (1942, Ghosts'n Goblins, Commando)
No/partial sound	YM2151 / GA20 / Z80	Sound-stage diagnosis	Irem M62 / M72 / M92 (R-Type & co.)
No/partial sound	YM2151/OKI (MS1) / YMF271 (MS32)	Sound-stage diagnosis	Jaleco (Mega System 1 / 32)
No/partial sound	YM2151 / OKI / customs	Sound-stage diagnosis	Kaneko (Kaneko 16, Super Nova System)
No/partial sound	K053260 / YM2151 / Z80	Sound-stage diagnosis	Konami — 68000 beat'em ups (TMNT, Simpsons, X-Men)
No/partial sound	YM2151 / C30 / sound 6809	Sound-stage diagnosis	Namco System 1
No/partial sound	C352	Sound-stage diagnosis	Namco System 11
No/partial sound	C352	Sound-stage diagnosis	Namco System 12
No/partial sound	C352	Sound-stage diagnosis	Namco System 22 / Super System 22
No/partial sound	C352 / sound H8	Sound-stage diagnosis	Namco System 23 (Gorgon / Super System 23)
No/partial sound	YMF278B (OPL4)	Sound-stage diagnosis	Psikyo (68020 / SH-2)
No/partial sound	YMZ280B / Z80	Sound-stage diagnosis	Raizing / Eighting (8ing)
No/partial sound	Seibu Sound System (Z80/YM/OKI)	Sound-module diagnosis	Seibu Kaihatsu (Raiden, SPI System)
No/partial sound	YM / sound Z80	Sound-stage diagnosis	SNK — before the Neo-Geo (Ikari Warriors, P.O.W.)
No/partial sound	YM2610 / Z80	Sound-stage diagnosis	Taito B System
No/partial sound	YM2610 / Z80	Sound-stage diagnosis	Taito F2 System
No/partial sound	ES5505/5510	Sound-stage diagnosis	Taito F3 System
No/partial sound	YM2610 / Z80	Sound-stage diagnosis	Taito Z System
No/partial sound	YM3812/YM2151 / OKI / Z80	Sound-stage diagnosis	Tecmo (Rygar, Ninja Gaiden, Silkworm)
No/partial sound	YM3812/YM2151 / OKI / sound MCU	Sound-stage diagnosis	Toaplan (V1 / V2)
Noise / hum	Filter caps	Recap	Repair: Sega power block (candy cab)
Noise in the sound	known on Mayjinsen 3	May be original	Aleck 64
Noisy sound/picture	tired caps	Targeted recap	Commodore CDTV
Permanent high-pitched whine	Buck converter inductor (discontinuous conduction)	3 coil whine fixes	Sega 32X
Silent board	V70 or its 40 MHz crystal	Two separate crystals: do not confuse them	Jaleco Mega System 32
Silent board	PowerPC 403GCX, 66 MHz oscillator, power	PCB diagnosis	Konami Firebeat
Silent board	68040, 10 MHz crystal, CY7C991	The CY7C991 is the CPU's clock source	Taito JC System
Silent board, no picture	E1-32N or its 45 MHz crystal	The processor is rare: check the clock before suspecting it	Eolith
Silent board, no picture	power, CPU, or a CPLD	PCB diagnosis	Konami Viper
Silent sound	YM2203/2608	Sound-stage diagnosis	NEC PC-8801 (PC-88) & PC-9801 (PC-98)
Silent/partial sound	V53A / L7A1045 DSP	Sound-stage diagnosis	SNK Hyper Neo Geo 64
Sound CPU crashes	known on II and V boards	The driver flags mishandled nested NMIs	Alpha Denshi / ADK
Sound skipping samples	NMK112 (bank switching)	An intermediate stage that is often forgotten	NMK 16-bit (NMK / UPL)
Turns off / restarts / PSU noise	PSU — tired caps	Recap or DreamPSU/PicoPSU	Sega Dreamcast
Voice/samples silent (C-2)	µPD7759	Sample-stage diagnosis	Sega System C / C-2
Weak / absent sound	Audio capacitors, speaker	Recap; speaker	Game Boy Advance
Wrong colours/sound	ASIC / caps	Recap, check the ASIC	Amstrad CPC Plus (464 Plus / 6128 Plus)
Wrong or unstable sound	CEM3394 or its analogue surroundings	⚠️ an analogue synth drifts normally — recap before concluding	Bally / Sente SAC-1
Wrong/no sound	AY-3-8912	Sound-stage diagnosis	Amstrad CPC (464 / 664 / 6128)

Media & drive (109)

Symptom	Probable cause	Next step	Page
Backup cartridge not recognised	Cartridge slot contacts	Cleaning	Sega Saturn
Cart contacts	slot/cart oxidation	Clean connectors (slot and cart)	SNK Neo-Geo cabinets (MVS)
Cart not read	PCMCIA contacts / RF5C296	Clean the contacts with isopropyl alcohol	Taito G-NET
Cartridge ignored	contacts / ASIC unlock sequence	Clean contacts, try another cart	Amstrad CPC Plus (464 Plus / 6128 Plus)
Cartridge not read	Connector oxidation	Cleaning	Atari 2600 (VCS)
Cartridge not read	Contacts	Cleaning	Atari 5200
Cartridge not read	Contacts	Cleaning	Atari 7800
Cartridge not read	Contacts	Cleaning	Atari Jaguar
Cartridge not read	Contacts	Cleaning	Atari Lynx
Cartridge not read	Contacts	Cleaning	Bandai WonderSwan
Cartridge not read	expansion-port contacts	Clean	Commodore 64 Games System (C64GS)
Cartridge not read	connector contacts	Isopropyl alcohol, never an abrasive	Epoch Super Cassette Vision
Cartridge not read	Contacts	Cleaning	GCE / MB Vectrex
Cartridge not read	connector contacts	Isopropyl alcohol, never an abrasive	Interton VC 4000 (and the 1292 family)
Cartridge not read	connector contacts	Isopropyl alcohol, never an abrasive	Mattel Intellivision
Cartridge not read	Connector oxidation	Cleaning	Sega Game Gear
Cartridge not read	Connector oxidation	Contact cleaning	Sega Master System (Mark III)
Cartridge not read	Connector oxidation	Clean the contacts	Sega SG-1000
Cartridge not read	Contacts	Cleaning	SNK Neo Geo Pocket (Color)
Cartridge not read	expansion-port contacts	Clean	Commodore 64
Cartridge not read / corrupt graphics	Oxidised AW cartridge contacts	Clean the edge + slot	Sammy Atomiswave
Cartridge not read / corrupted graphics	Cartridge contacts / customs	Clean contacts, reseat	Capcom CPS Changer
Cartridge not read / corrupted graphics	Cartridge connector oxidation	Clean with iso alcohol	Sega Mega Drive / Genesis
Cartridge not read / corrupted graphics	Slot oxidation / cart contacts	Clean the slot and cartridge edge	SNK Neo-Geo MVS
Cartridge not read / crash	oxidised cart contacts	Clean the connector (isopropyl alcohol)	Amstrad GX4000
Cartridge not read / crash	Cartridge contacts	Cleaning	Nintendo 64
Cartridge not read / crash	Cartridge connector oxidation	Contact cleaning	SNK Neo-Geo AES
Cartridge not read / crash	Oxidised cartridge slot contacts	Clean the cartridge edge + the slot	Sega ST-V (Titan Video)
Cartridge not read / crash	cartridge slot contacts	Clean edge + slot	Taito F3 System
Cartridge not read / frozen screen	Cartridge connector oxidation	Cleaning (iso alcohol), no abrasive	Super Nintendo / Super Famicom (SNES / SFC)
Cartridge not recognised	connector contacts	Isopropyl, never an abrasive	Bit Corporation Gamate
Cartridge not recognised	connector contacts	Clean with isopropyl, never an abrasive	Emerson Arcadia 2001
Cartridge not recognised	connector contacts	Isopropyl, never an abrasive	Watara Supervision
Cartridge not recognised	connector contacts	Isopropyl, never an abrasive	Mattel Aquarius
Cartridge not recognised	RP5H01 (PC-10) / contacts	Clean the connector	Nintendo — arcade (VS. System, PlayChoice-10, Super System)
Cartridge/ROM not read	Contacts	Cleaning	Sega System E
Cassette load fails	level / drive	Adjust, clean	Oric-1 & Oric Atmos
Cassette not read (DECO Cassette)	drive / dead cassette	Repair/image; rare part	Data East (DECO Cassette, DECO 8/16/32)
CD load errors	Worn SCSI CD drive / damaged CD	Repair/replace drive, or SD multi	Capcom CP System III (CPS-3)
CD not read	belt/laser/caddy	Clean optics, belt, adjust laser	Commodore CDTV
CD not read	belt / laser	Optical clean, belt, ODE	Fujitsu FM Towns Marty
CD not read	belt / laser / caddy	Clean optics, belt, ODE	Fujitsu FM Towns (& FM Towns Marty)
Contacts / card reader	Wear	Cleaning	Nintendo DS
Dark / unreadable screen	Reflective stock LCD	IPS screen (mod)	Game Boy / Game Boy Color
Data Pack wiped/unreadable	power-on pulse / mechanism	Remove tape before power-on; service drive	Coleco Adam
Dead cartridge / won't boot	Flat battery (suicide)	Phoenix / no-battery, or SD multi	Capcom CP System III (CPS-3)
Dead ports/keyboard/floppy	CIA 8520	Substitute the CIA(s)	Commodore Amiga
Disc Read Error (fat)	Worn laser / rail / gears	Adjust/replace the laser, or load without a disc (FMCB + USB/HDD)	Sony PlayStation 2 (PS2)
Disk not read (6128 Plus)	perished belt / dirty head	Replace belt, clean head	Amstrad CPC Plus (464 Plus / 6128 Plus)
Disk not read (664/6128)	perished belt / head	Replace belt, clean	Amstrad CPC (464 / 664 / 6128)
Disk read error	hard disk at end of life	The dominant failure point on a 1999 machine	Konami Twinkle
Disk unreadable	HDD worn out	An arcade hard disk runs for years without stopping	Namco System 357 / 369
Drive not detected	SIO bus	Cable / drive PSU	Atari 8-bit (400 / 800 / XL / XE)
Erratic tray (Model 1)	Dirty limiter switches; faulty helix screw on Sony drives	Clean the switches; drive mechanism	Sega Mega-CD / Sega CD
Fat: DVD reading fails	Tired KHS-400 laser	Replace the laser	Sony PlayStation 2 (PS2)
Floppy not read	3.5″ mechanism	Clean / Gotek	Acorn Archimedes
Floppy not read	3″ drive belt	Replace the belt	Amstrad PCW (8256 / 8512 / 9512)
Floppy not read	Disk II speed / head	Adjust speed, clean	Apple II (II / II+ / IIe / IIc / IIGS)
Floppy not read	mechanism / SWIM	Service / Floppy Emu	Apple Macintosh compact (128K → SE/30)
Floppy not read	mechanism / head	Clean, Gotek	Atari ST (520/1040, STE, Mega, Falcon)
Floppy not read	mechanism / belt	Clean / Gotek	Fujitsu FM-7 / FM-8 (& FM77)
Floppy not read	3.5″ mechanism	Clean / Gotek	Fujitsu FM Towns (& FM Towns Marty)
Floppy not read	3.5″ drive	Clean / Gotek	MGT SAM Coupé
Floppy not read	mechanism / format	Clean, Gotek	NEC PC-8801 (PC-88) & PC-9801 (PC-98)
Floppy not read	5.25″ mechanism	Clean / Gotek	Sharp X68000
Floppy not read	mechanism / belt	Clean / Gotek	Tandy TRS-80 Model I / III / 4
Floppy unreadable	the controller board or the drive	⚠️ the board is repairable, see below	Apple Lisa
Floppy unreadable	WD1770 (I042) or the mechanism	Expected clock: 8 MHz	Tatung Einstein
Floppy unreadable (Disc2)	Z80 4 MHz or the μPD765A	The expansion has its own logic	Micronique Hector
Floppy unreadable (mini Disc)	FD1793	A different controller, no second Z80	Micronique Hector
GD read errors	Worn GD-ROM drive	Repair/replace, or netboot (removes the GD)	Sega NAOMI
GD-ROM won't load	GD drive / DIMM / RTC battery	See NAOMI	Sega NAOMI Universal Cabinet
HuCard not read	Connector contacts	Cleaning	NEC PC Engine / TurboGrafx-16
IC-card reading fails	R5F21256SN (the “MPU”)	MCU dedicated to that function	IGS PGM2
Import game refused, or CD unit won't work with the console	Double region lock (game and host console)	Region-free BIOS	Sega Mega-CD / Sega CD
Jaguar CD won't read	Laser / add-on	Repair / ODE	Atari Jaguar
Loading/tray dead	Belt / mechanism	Replace belt, clean the rail	SNK Neo Geo CD
Memory card not read	Contacts	Cleaning	Nintendo GameCube
Microdrive unreadable (QL)	tape / pad	Clean, replace pad	Sinclair ZX80 · ZX81 · QL
Multi-slot selector dead	selection logic / switch	Check the selection circuit	SNK Neo-Geo cabinets (MVS)
One specific cartridge won't run	⚠️ may be normal	See the incompatibilities above	Philips Videopac G7000 and Videopac+ G7400
Pale or unreadable image	manual contrast or the panel	The screen is not backlit: judge it in good light	Bit Corporation Gamate
Read skips	Weak laser	Adjust the laser pot; ODE	Sony PlayStation (PS1)
Smeary colours on SCART	RGB cable/mod	Check the RGB SCART wiring	European cabinets
System Card not read	HuCard contacts	Cleaning	PC Engine CD-ROM² / Duo
Tape unreadable	cassette stage	A dedicated schematic is archived	Philips VG-5000
Tape/QDD not read	head / belt	Clean, mechanical check	Thomson (MO5 / MO6 / TO7 / TO8 / TO9)
Tray won't fully open/close, laser no longer lifts (Model 1)	Overstretched belt (the Model 1's number-one fault)	Replace the belt — square 24 × 1.2 mm	Sega Mega-CD / Sega CD
Tray/loading fails (Model 1)	Broken plastic gear	Replace the Model 1 gear (a known part)	Sega Mega-CD / Sega CD
UMD won't read	Optical drive / mechanism	Clean, or go download-based (CFW + Memory Stick)	Sony PSP (PlayStation Portable)
Unreadable screen without strong light	Reflective LCD (AGB)	IPS screen (mod)	Game Boy Advance
Will not boot with the cartridge	cartridge contacts, or the IGS036	Clean the contacts with isopropyl alcohol	IGS PGM2
Will not boot, read error	hard disk or CD at end of life	Image the media while it still reads	Konami Firebeat
Will not read the CD	worn optical drive	The dominant failure point on any CD machine	Bandai Pippin (@WORLD / ATMARK)
Will not read the CD	worn CD drive (lens, rails)	The dominant failure point on any CD machine	Konami GV (“Baby Phoenix”)
Will not read the CD	worn CD drive	The dominant failure point on any CD machine	Konami M2
Won't load	drive (belt/head)	Mechanism, belts	Sharp X1 & MZ
Won't read / only reads upside down	Worn laser / rail / gears	Adjust the laser, replace the optical block, or ODE	Sony PlayStation (PS1)
Won't read CDs	Worn laser	Adjust/replace, ODE	3DO Interactive Multiplayer
Won't read CDs	Worn / misaligned laser	Adjust/replace, or ODE	PC Engine CD-ROM² / Duo
Won't read CDs	Worn laser / optical block	Adjust/replace, or ODE (image it first)	NEC PC-FX
Won't read CDs	Worn laser / optical block	Adjust/replace, image it first	Philips CD-i
Won't read CDs	Worn laser / optical block	Adjust/replace the laser, or ODE	Sega Saturn
Won't read CDs / erratic reads	Worn / misaligned laser	Adjust the laser pot, or replace the optical block	Sega Mega-CD / Sega CD
Won't read CDs / random reads	Worn laser / optical block	Adjust/replace, or ODE (image it first)	SNK Neo Geo CD
Won't read discs	Worn optical drive	GC Loader ODE (SD), or replace the drive	Nintendo GameCube
Won't read GDs	Worn laser	ODE (GDEMU/MODE) — recommended	Sega Dreamcast
Won't start on cartridge	cartridge contacts	Clean the connector	Texas Instruments TI-99/4A
Won't start with a cartridge	slot contacts	IPA clean, try another cart	MSX (MSX / MSX2 / MSX2+ / turbo R)

Controls (42)

Symptom	Probable cause	Next step	Page
Analogue controls wrong	ADC0838 (U13) or wiring	Compare input voltages against a good board	Konami Viper
Analogue joysticks dead	ADC0844 (I050)	Dedicated conversion circuit	Tatung Einstein
Controller (SG-1000)	Cable/solder joints	Re-solder / replace	Sega SG-1000
Controller not recognised	ADB through the Cuda	The Pippin uses the Macs' ADB bus	Bandai Pippin (@WORLD / ATMARK)
Controls / gun dead	I/O H8/PIC / harness	I/O diagnosis	Namco System 23 (Gorgon / Super System 23)
Controls dead	TC0640FIO or wiring	Proprietary I/O, not JAMMA	Taito JC System
Controls dead	TC0510NIO	Taito proprietary I/O	Taito Wolf System
Controls dead	proprietary wiring	⚠️ not JAMMA: nothing from the standard loom applies	Zaccaria
Dead 2-player link	the DE-9 connector or its cable	An external, accessible failure point	Watara Supervision
Dead button	Membrane / ribbon	Replace the ribbon	Sony PSP (PlayStation Portable)
Dead controls	JAMMA harness / microswitches	Diagnose I/O, clean contacts	Capcom cabinets (Mini Cute, Impress, Status)
Dead controls	JAMMA harness / microswitches	Diagnose I/O, clean contacts	European cabinets
Dead controls	JAMMA harness / microswitches	Diagnose I/O, clean	Irem Madonna / Madonna 33
Dead controls	JAMMA harness / microswitches	Diagnose I/O, clean	Jaleco — Pony cabinets
Dead controls	JAMMA/JVS / harness	I/O diagnosis	Namco cabinets (Noir, Exceleena, Cyberlead)
Dead controls	JVS I/O / harness	Diagnose JVS	Sega Lindbergh (cabinets)
Dead controls	JVS I/O / JVS harness	Check the JVS I/O board + cable	Sega NAOMI Universal Cabinet
Dead controls	JVS I/O / harness	JVS diagnosis	Sega New Net City
Dead controls	JAMMA harness / microswitches	Diagnose I/O, clean	Taito Canary
Dead controls	JVS I/O / harness	JVS diagnosis	Taito Vewlix
Dead controls	harness / dedicated I/O	Check the wiring	Sega Model 1
Dead controls (one side)	that panel's harness	Diagnose the faulty side's I/O	Sega Aero Table
Dead keyboard/mouse	IKBD 6301 / link	Diagnose the microcontroller	Atari ST (520/1040, STE, Mega, Falcon)
Erratic trackball	trackball optics / bearing	Clean / replace optics	Incredible Technologies (Golden Tee)
Flaky buttons/stick	Worn microswitches, CP harness	Replace switches	Sega Astro City
Flaky controller	Worn port / dead series diode or resistor	Replace the component	Sega Mega Drive / Genesis
Flaky dual joystick	contacts/switches	Clean/replace	Nichibutsu (Crazy Climber, Moon Cresta, Terra Cresta)
Flaky L/R buttons	Worn switches	Replace/clean	Nintendo DS
Front button does nothing	Dirty tactile switch	Test continuity; replace (SPST 12 × 12 mm, ~4.5 mm)	Atari 7800
I/O not responding	JVS I/O board / wiring	Check JVS, I/O power	Sega NAOMI
Imprecise analog stick	Worn/dirty nub	Clean / replace the nub	Sony PSP (PlayStation Portable)
Imprecise gun (440)	optics / calibration	Clean, recalibrate	Exidy (Venture, Crossbow, Mouse Trap)
Imprecise rotary joystick	LOOP mechanism / optics	Clean/repair the rotary stick	SNK — before the Neo-Geo (Ikari Warriors, P.O.W.)
Imprecise stick	Worn microswitches	Replace the switches	SNK Neo Geo Pocket (Color)
Inconsistent controls or I/O	I/O map handled by a PAL	⚠️ partly undocumented	Bally / Midway MCR
Keyboard partly dead	74LS156 (decoder, column select) / 74LS148 (priority encoder, return) or the matrix	⚠️ not the 8243 — see below	Philips Videopac G7000 and Videopac+ G7400
Light pen not working	sensor / dedicated circuit	Light-pen diagnosis	Thomson (MO5 / MO6 / TO7 / TO8 / TO9)
Loose / imprecise stick (controller)	Analog stick wear	Replace with a new stick (GameCube-type kit)	Nintendo 64
Loose / off-center stick	Worn analog joystick	Controller repair kit (the most common)	Atari 5200
No controls	I/O board or JVS wiring	→ JVS wiring	Namco System 357 / 369
One player unresponsive	multiplayer I/O / harness	Check player wiring	Konami — 68000 beat'em ups (TMNT, Simpsons, X-Men)
Wheel/pedals dead	TC0220IOC / harness	I/O diagnosis	Taito Z System

Save, settings & protection (92)

Symptom	Probable cause	Next step	Page
"Backup RAM error"	Flat battery / SRAM	Clear via BIOS/UniBIOS; replace the battery	SNK Neo-Geo MVS
"Security check"	the game's custom security chip	Check the chip; MAME documents the exchange	Sega Model 2
"Security" / tilegen	protection (encrypted data)	MAME/Supermodel document it; custom diagnosis	Sega Model 3
Battery (RTC/save)	Flat battery	Replace	3DO Interactive Multiplayer
Battery contact corrosion	Leaked batteries	Clean the contacts	Atari Lynx
Battery contact corrosion	Leaked battery	Clean the contacts	Bandai WonderSwan
Battery contact corrosion	Leaked batteries	Clean / rebuild the contacts	Game Boy / Game Boy Color
Battery contact corrosion	Leaked batteries	Clean contacts	Game Boy Advance
Battery contact corrosion	Leaked batteries	Clean the contacts	SNK Neo Geo Pocket (Color)
Clock "wrong" at 5.09 MHz	none — that is the exact value	See the note above	Apple Lisa
Clock "wrong" on a TV Link	nothing — the frequency depends on the model	See the variants table	Watara Supervision
Clock / saves lost	Flat CR2032 battery	Replace the battery	Sega Saturn
Clock resets	Flat rechargeable battery	Replace (holder + coin cell)	Sega Dreamcast
Corroded traces near the battery	Battery leak	Remove the battery, clean, repair the traces (wire / jumper)	SNK Neo-Geo MVS
Corrosion / wrong clock	RTC battery	Remove, repair traces	Acorn Archimedes
Corrosion / wrong clock (98)	leaked CMOS battery	Remove, repair traces	NEC PC-8801 (PC-88) & PC-9801 (PC-98)
Corrosion near the battery	leaking PRAM	Remove, neutralize, repair	Apple Macintosh compact (128K → SE/30)
Corrosion near the battery	backup battery leaking	See the box — take the battery out first	Dynax
Corrosion near the battery	battery on the main RAM	Take the battery out before any diagnosis	IGS011 (blitter hardware)
Corrosion near the clock	leaked NVRAM battery	Remove battery, clean/repair traces	Commodore CDTV
Corrosion near the clock	leaked battery	Remove, neutralise, repair traces	Commodore Amiga
Corrosion near the clock	RTC battery	Remove, repair traces	Sharp X68000
Dead battery (games)	MVS save	See Neo-Geo MVS	SNK Neo-Geo cabinets (MVS)
Hangs / lost settings	Flat NVRAM Timekeeper (battery)	Replace the battery-backed chip	Philips CD-i
Lost clock / corrosion	CMOS/barrel battery	Remove, repair traces	IBM PC & compatibles (DOS gaming)
Lost config	EEPROM / battery	Reinit / replace	Atari — arcade (System 1/2, Hard Drivin')
Lost config	EEPROM / battery	Reinit (TEST at boot); see converts	Konami GX (System GX)
Lost save (game)	Flat cartridge battery (CR2032/CR1616)	Replace the battery in the cartridge	Super Nintendo / Super Famicom (SNES / SFC)
Lost save (game)	Flat cartridge battery	Replace the battery in the cartridge	SNK Neo-Geo AES
Lost saves	Flat BRAM battery (RTC/internal saves)	Replace the battery; FX-BMP as backup	NEC PC-FX
Lost saves	Flat internal RAM battery (or supercapacitor on the X'Eye)	Replace the battery, or switch to FRAM (no battery at all)	Sega Mega-CD / Sega CD
Lost saves	Flat backup battery	Replace the battery	SNK Neo Geo CD
Lost settings	DIPs misset	Check the DIP bank	Capcom — pre-CPS classics (1942, Ghosts'n Goblins, Commando)
Lost settings	DIP	Check the DIP bank	Irem M62 / M72 / M92 (R-Type & co.)
Lost settings	DIP	Check the DIP bank	Jaleco (Mega System 1 / 32)
Lost settings	DIP / EEPROM	Check DIP	Kaneko (Kaneko 16, Super Nova System)
Lost settings	DIP	Check the DIP bank	Konami — 68000 beat'em ups (TMNT, Simpsons, X-Men)
Lost settings	DIPs misset	Check the DIP bank	Konami — classics (Frogger, Scramble, Time Pilot, Gyruss)
Lost settings	DIPs misset	Check the DIP bank	Namco — classic hardware (Pac-Man / Galaga / Dig Dug / Xevious)
Lost settings	DIP / MCU	Check DIP, I/O	Namco System 1
Lost settings	RTC/config battery	Replace	Namco System 10
Lost settings	RTC/config battery	Replace	Namco System 11
Lost settings	RTC/config battery	Replace	Namco System 12
Lost settings	DIP	Check the DIP bank	Nichibutsu (Crazy Climber, Moon Cresta, Terra Cresta)
Lost settings	DIP / EEPROM	Check DIP	Psikyo (68020 / SH-2)
Lost settings	DIP	Check the DIP bank	Sega System E
Lost settings	DIPs misset	Check the DIP bank	Sega System 1 / System 2
Lost settings	DIP	Check the DIP bank	SNK — before the Neo-Geo (Ikari Warriors, P.O.W.)
Lost settings	DIP	Check the DIP bank	Taito B System
Lost settings	DIP	Check the DIP bank	Taito F2 System
Lost settings	DIP	Check the DIP bank	Tecmo (Rygar, Ninja Gaiden, Silkworm)
Lost settings	DIP	Check the DIP bank	Universal (Mr. Do!, Space Panic, Lady Bug)
Lost settings / region	Flat battery (RTC/config)	Replace the battery	Sega ST-V (Titan Video)
Lost settings / scores	Flat / leaking CMOS battery	Replace the battery; clean the corrosion	Midway T-Unit (Mortal Kombat II, NBA Jam…)
Lost settings / scores	EEPROM + battery per game	Replace the battery; no program "suicide"	Namco System 2
Lost settings / scores, "factory settings"	Flat / leaking CMOS battery	Replace the battery; clean the corrosion (possible trace damage)	Williams 6809 (Defender, Robotron, Joust…)
Lost settings/scores	93C46 EEPROM	Reprogram/replace	Cave (68000 hardware)
Lost settings/scores	Flat/leaking CMOS battery	Replace + clean corrosion	Midway — Y-Unit, Wolf-Unit, V-Unit, Seattle, Zeus
Lost settings/scores	EEPROM / battery	Reprogram/replace	Raizing / Eighting (8ing)
Memory card	(saves on external card)	Replace the card	Sony PlayStation (PS1)
Nothing starts, no clocks	42 MHz crystal	Both clocks derive from it	Data East MLC
Nothing starts, no clocks at all	14.31818 MHz crystal	Everything derives from it: one possible cause	Bally / Midway Astrocade
Nothing starts, no clocks at all	25 MHz crystal	All four clocks derive from it: one cause	Deniam
Nothing starts, no clocks at all	49.152 MHz master crystal	All three clocks derive from it: only one possible cause	Namco ND-1
One clock wrong	the matching divider	The crystal is fine if the others are	Deniam
One clock wrong	the matching divider (÷2, ÷3 or ÷4)	The crystal is fine if the other two are	Namco ND-1
Protection check failed	IGS003 or IGS012	Check which chips are fitted on your revision	IGS011 (blitter hardware)
Region/settings	DIP / region jumper	Check DIP + jumper	Toaplan (V1 / V2)
Security check failed	SPU / dongle / cart depending on the game	Check the original pairing	Konami Firebeat
Security check failed	DS2430 or a missing/wrong dongle	Check the board/dongle pairing for that game	Konami Viper
Settings lost	93C45 EEPROM	Pressing test restores the defaults	Data East MLC
Settings lost	board depending	—	Jaleco Mega System 32
Settings lost	25C EEPROM	⚠️ it is also the pairing chip — be careful before touching it	Konami GV (“Baby Phoenix”)
Settings lost	EEPROM	⚠️ MAME reports EEPROM failures on some games	Aleck 64
Settings lost	NVRAM (at $ff0000 on Lucky Boom)	⚠️ the exact chip type is not documented in MAME	Playmark
Settings lost	DIP / battery	Check DIP / replace battery	Sega System C / C-2
Settings lost	battery / EEPROM	Reset / replace	SNK Hyper Neo Geo 64
Settings lost at boot	PRAM battery flat	The classic symptom on Macs of this generation	Bandai Pippin (@WORLD / ATMARK)
Settings lost at every power-off	Dead battery	Replace the battery / holder	SNK Neo-Geo MVS
Settings/diagnostics	—	UniBIOS (test menu)	SNK Neo-Geo AES
Settings/scores lost	battery / backup SRAM	Replace battery, check SRAM	Incredible Technologies (Golden Tee)
Swelling battery	Aged Li-ion cell	Replace the battery (safety)	Sony PSP (PlayStation Portable)
Time and scores lost	normal — no non-volatile memory	See the box	Nintendo Game & Watch
Won't boot / wrong region	BIOS region setting	Check the BIOS key/region	Sammy Atomiswave
Wrong clock / corrosion	CMOS battery	Remove, repair traces	Fujitsu FM Towns Marty
Wrong clock / corrosion	CMOS battery	Remove, repair traces	Fujitsu FM Towns (& FM Towns Marty)
Wrong region	key / region byte	See converts (bi-region)	Taito F3 System
Wrong settings	DIP switches	⚠️ some MAME settings are marked unverified, from the manual	Seta
Z80 clock “wrong” on Hole Land	nothing — 3.3557 MHz is the normal value	See the box above	Tecfri
“RTC BAD” then reset loop	M48T58Y at end of life	Programme a new M48T58Y with the game's data — see the box	Konami Viper
“Wrong” clock	possibly nothing	⚠️ the frequency varies by model	Interton VC 4000 (and the 1292 family)
“Wrong” clocks	possibly nothing	⚠️ the sound board's dividers are unknown	Bally / Sente SAC-1

Wiring & connectors (8)

Symptom	Probable cause	Next step	Page
32X and/or MD damaged after a home-made cable	+5 V pin wired on the cable going to the 32X	⚠️ See the danger box in A/V wiring	Sega 32X
Image shrinks / blooms	dried electrolytics (recap), drifting +B	Recap, measure +B	Repair: Wells-Gardner monitors
JAMMA contacts	oxidation	Clean the card edge	Konami Windy / Windy II
JAMMA contacts	oxidation	Clean the edge connector	Sammy Atomiswave SD
JAMMA contacts	oxidation	Clean the card edge	Taito Egret II / II Mini
JAMMA contacts	oxidation	Clean the edge connector	Taito Egret 3
No communication with the MD	Connector/contacts	Clean the expansion bus	Sega Mega-CD / Sega CD
Power that cuts out and returns when the cable is moved	Internal break in the cable (very thin from the factory)	Repair the brick's cable	Atari 7800

Screen & picture (339)

Symptom	Probable cause	Next step	Page
2nd screen dead (Multi 32)	dual-screen output/harness	Check the 2nd video output	Sega System 32
2nd screen dead (Type 3/4)	dual-screen output/harness	Check the 2nd output	Konami GX (System GX)
32X image jitters then locks up after ~1 h warming up	EDCLK/VCLK not clean enough on a Model 1 MD (VA4 / VA5-6.8)	Sega service bulletin fixes	Sega 32X
Abnormal graphics	the E90 board	Its operation is undocumented — comparison is mandatory	Aleck 64
Black screen	RAM / OS ROM / GTIA	Substitute	Atari 8-bit (400 / 800 / XL / XE)
Black screen	buffers / VDP / CPU	Substitute	Texas Instruments TI-99/4A
Black screen / checkerboard	RAM / PLA / CPU	Test, substitute	Commodore 8-bit — VIC-20 · C128 · C16/Plus4 · PET
Black screen / stuck boot	FD1089/FD1094: dead key battery	De-suicide (decrypted ROM / re-key)	Sega "Super Scaler" (Hang-On / Space Harrier / OutRun)
Black screen / stuck boot	MC-8123: dead key battery (encrypted games)	Re-key / decrypted ROM (see per-game keys)	Sega System 1 / System 2
Black screen / stuck boot	Suicide: dead battery-backed security module	De-suicide (decrypted ROM) — see the link above	Sega System 32
Black screen / stuck boot	FD1094: dead key battery (encrypted games)	De-suicide (decrypted ROM / re-key)	Sega X-Board
Black screen / stuck boot	FD1094: dead key battery (encrypted games)	De-suicide (decrypted ROM / re-key)	Sega Y-Board
Black screen, board powered	315-5195 mapper, 68000, reset	PCB diagnosis	Sega System 18
Blur	flyback focus pot	Adjust / replace the flyback	Repair: Hantarex monitors
Blur	flyback focus	Adjust / replace flyback	Repair: Sanwa monitors (Sanwa Denshi)
Blur / defocus	flyback focus pot, tired flyback	Adjust focus, replace flyback	Repair: Wells-Gardner monitors
Blur / washed-out colours	flyback focus / neck board	Adjust focus, diagnose the neck board	Repair: Nanao MS2930 / MS2931 / MS2932 / MS2933 (tri-sync)
Blur / washed-out colours	flyback focus / neck board	Adjust focus, diagnose neck board	Repair: Toshiba PB-7534 (Konami Windy 2)
Blurred / ghosting image	⚠️ may be the original screen	See below	Watara Supervision
Blurry image / lack of focus	Focus adjustment, aging flyback	Adjust focus; flyback if dead	Repair: Nanao MS8 monitor
Characters correct, or replaced by semigraphics of arbitrary colour	attribute RAM (ref. 666)	Same	Philips Videopac G7000 and Videopac+ G7400
Colour patches on screen	Magnetised shadow mask	Degauss	Sega Astro City
Colour smearing	Failed EMI filters — a known Saturn fault	Replace the EMI filters	Sega Saturn
Completely black screen (G7400)	⚠️ VIN or VDOP — see below	Mutual dependency: the VDOP is slave to the VIN, but the VIN is blocked without the VDOP's HSY	Philips Videopac G7000 and Videopac+ G7400
Corrupt B&W image	video RAM, Z80	RAM test, contacts	Sega / Gremlin VIC Dual
Corrupt bitmap image (SI)	video RAM / 8080	RAM test, contacts	Taito — classics (Space Invaders, Qix, Bubble Bobble…)
Corrupt graphics	Tom custom (Jaguar)	No replacement — diagnose by comparison	Atari Cojag
Corrupt graphics	RAM on the lower board	Separate the two boards before probing	Data East MLC
Corrupt graphics	IGS011 blitter	No replacement: comparison is mandatory	IGS011 (blitter hardware)
Corrupt graphics	IGS037 or the SRAM	Diagnose by comparison — no replacement chips	IGS PGM2
Corrupt graphics	Fujitsu SGRAM or the Voodoo III	A single corrupt area points at one of the four chips	Konami Viper
Corrupt graphics	video RAM / NAND	RAM test, NAND dump	Namco System 10
Corrupt graphics	video RAM / ROM board	RAM test, contacts	Namco System 11
Corrupt graphics	video RAM / ROM board	RAM test, contacts	Namco System 12
Corrupt object image	object framebuffer / RAM	RAM test, contacts	Namco System 21 "Polygonizer"
Corrupt or missing graphics	TC17G032AP-0246 blitter	No replacement: comparison is mandatory	Dynax
Corrupt or missing sprites	X1-001 custom	No replacement: diagnose by comparison	Seta
Corrupt raster image	video RAM, Z80	RAM test, contacts	Sega G80 (raster & vector)
Corrupt sprites	sprite generator (6 MHz)	Derived from the 48 MHz	Jaleco Mega System 32
Corrupt sprites	Video System sprite generator	Custom: diagnose by comparison	Video System
Corrupt sprites or planes	GAE1 / CG-1V custom or video RAM	Compare against a good board	Gaelco
Corrupt sprites or planes	video RAM or logic	Compare against a good board	Technos Japan
Corrupt sprites/3D	TMS34010 / Voodoo (Seattle/Zeus)	Video diagnosis per generation	Midway — Y-Unit, Wolf-Unit, V-Unit, Seattle, Zeus
Corrupt sprites/layers	one of the 2 VDPs / VRAM	Isolate the faulty VDP, RAM test	Sega System E
Corrupt sprites/planes	Atari customs / RAM	RAM test, contacts	Atari — arcade (System 1/2, Hard Drivin')
Corrupt sprites/planes	013/038 customs / RAM	RAM test, contacts; rare customs	Cave (68000 hardware)
Corrupt sprites/planes	customs / RAM	RAM test, contacts	Data East (DECO Cassette, DECO 8/16/32)
Corrupt sprites/planes	Nanao customs / RAM	RAM test, contacts	Irem M62 / M72 / M92 (R-Type & co.)
Corrupt sprites/planes	customs / RAM	RAM test, contacts	Jaleco (Mega System 1 / 32)
Corrupt sprites/planes	Kaneko customs (VU-xxx) / RAM	RAM test, contacts	Kaneko (Kaneko 16, Super Nova System)
Corrupt sprites/planes	K052109/K051960 customs / RAM	RAM test, contacts; rare customs	Konami — 68000 beat'em ups (TMNT, Simpsons, X-Men)
Corrupt sprites/planes	customs / RAM	RAM test, contacts	Konami Gradius / Nemesis / Twin16 (shmups)
Corrupt sprites/planes	GX customs / RAM	RAM test, contacts; rare customs	Konami GX (System GX)
Corrupt sprites/planes	video RAM, customs	RAM test, contacts	Namco System 1
Corrupt sprites/planes	video customs (C116 palette…), RAM	RAM test, contacts; customs are rare	Namco System 2
Corrupt sprites/planes	Psikyo customs / RAM	RAM test, contacts	Psikyo (68020 / SH-2)
Corrupt sprites/planes	GP9001 / RAM	RAM test, contacts; rare custom	Raizing / Eighting (8ing)
Corrupt sprites/planes	video RAM, sprite customs	RAM test, contacts	Sega System 32
Corrupt sprites/planes	customs / RAM	RAM test, contacts	Seibu Kaihatsu (Raiden, SPI System)
Corrupt sprites/planes	customs / RAM	RAM test, contacts	SNK — before the Neo-Geo (Ikari Warriors, P.O.W.)
Corrupt sprites/planes	TC0xxx customs / RAM	RAM test, contacts	Taito B System
Corrupt sprites/planes	TC0xxx customs / RAM	RAM test, contacts	Taito F2 System
Corrupt sprites/planes	Taito customs / RAM	RAM test, contacts	Taito F3 System
Corrupt sprites/planes	customs / RAM	RAM test, contacts	Tecmo (Rygar, Ninja Gaiden, Silkworm)
Corrupt sprites/planes	GP9001 / RAM (V2)	RAM test, contacts; rare custom	Toaplan (V1 / V2)
Corrupt sprites/tiles	video RAM, customs	RAM test, contacts	Capcom — pre-CPS classics (1942, Ghosts'n Goblins, Commando)
Corrupt sprites/tiles	video RAM, 6502	RAM test, contacts	Exidy (Venture, Crossbow, Mouse Trap)
Corrupt sprites/tiles	video RAM, 6502	RAM test, contacts	Gottlieb (Qbert, Reactor, Mad Planets)
Corrupt sprites/tiles	video RAM, Z80	RAM test, contacts	Konami — classics (Frogger, Scramble, Time Pilot, Gyruss)
Corrupt sprites/tiles	video RAM, Z80	RAM test, contacts	Namco — classic hardware (Pac-Man / Galaga / Dig Dug / Xevious)
Corrupt sprites/tiles	video RAM, CPU	RAM test, contacts	Nichibutsu (Crazy Climber, Moon Cresta, Terra Cresta)
Corrupt sprites/tiles	video RAM, customs	RAM test, contacts	Sega System 1 / System 2
Corrupt sprites/tiles	video RAM, customs	RAM test	Taito — classics (Space Invaders, Qix, Bubble Bobble…)
Corrupt sprites/tiles	video RAM, Z80	RAM test, contacts	Universal (Mr. Do!, Space Panic, Lady Bug)
Corrupt video	Gate Array / CRTC / RAM	Substitute, RAM test	Amstrad CPC (464 / 664 / 6128)
Corrupt video	VRAM / VDP	Substitute VRAM, test VDP	MSX (MSX / MSX2 / MSX2+ / turbo R)
Corrupt video	VRAM / GDC	Substitute VRAM, test GDC	NEC PC-8801 (PC-88) & PC-9801 (PC-98)
Corrupted / missing graphics	B-board contacts, customs, ROMs	Reseat, connector cleaning	Capcom CP System (CPS-1)
Corrupted 3D	custom video hardware	Video diagnosis	SNK Hyper Neo Geo 64
Corrupted bitmap image	Video RAM / bank switching	RAM test, contacts	Williams 6809 (Defender, Robotron, Joust…)
Corrupted graphics	ROMs / B-board contacts	Reseat, connector cleaning	Capcom CP System II (CPS-2)
Corrupted graphics	Flash SIMMs / contacts	Reflash SIMMs, reseat	Capcom CP System III (CPS-3)
Corrupted graphics	ITV4400 blitter / IT42 / VRAM	Video diagnosis, reseat	Incredible Technologies (Golden Tee)
Corrupted graphics / sprites	Customs, ROMs, contacts	Reseat, cleaning	Sega System 16
Corrupted sprites / page flipping	Video RAM / TMS34010	RAM test, contacts	Midway T-Unit (Mortal Kombat II, NBA Jam…)
Crash / unstable image	RAM, interconnects, weak power	Reseat, RAM test, targeted recap	Sega Model 1
Crashes / corrupted graphics	+5 V too low (harness drop)	Adjust +5 V at the edge under load	Power supplies in cabinets
Dark / absent image / lines	Capacitors / screen / joints	Recap; else a McWill screen	Sega Game Gear
Dark / dim screen	Reflective stock	Frontlight / IPS (mod)	Bandai WonderSwan
Dark / failing screen	Stock backlight	IPS screen (McWill)	Atari Lynx
Dark screen	Reflective stock	Frontlight / backlight (mod)	SNK Neo Geo Pocket (Color)
Dead picture	CRT / PSU	CRT safety first	Amstrad PCW (8256 / 8512 / 9512)
Dead picture (all-in-one MZ)	CRT / video board	CRT safety first	Sharp X1 & MZ
Dead picture (PET)	CRT / PSU / deflection	CRT safety first	Commodore 8-bit — VIC-20 · C128 · C16/Plus4 · PET
Dead screen (HV ok)	Vector stage / dead caps	Recap + diagnosis	Atari — vector games (Asteroids, Tempest…)
Dead screen (HV ok)	vector generator / caps	Recap + diagnosis	Cinematronics (vector)
Dead screen (III/4)	CRT / PSU	CRT safety first	Tandy TRS-80 Model I / III / 4
Dead screen, HV ok (vector)	vector generator / caps	Recap + diagnosis	Sega G80 (raster & vector)
Degraded image	Composite output / joints	Check, mod if needed	Atari 7800
Distorted / missing lines	XY deflection stage, cold joints	Reflow, deflection diagnosis	Atari — vector games (Asteroids, Tempest…)
Distorted/missing lines	XY deflection / joints	Reflow, deflection diagnosis	Cinematronics (vector)
Distorted/missing lines (6100 vector)	XY deflection / joints / generator	Reflow, deflection diagnosis; ⚠️ static spot = phosphor burn	Repair: Wells-Gardner monitors
Distorted/missing lines (vector)	XY deflection / joints	Reflow, deflection diagnosis	Sega G80 (raster & vector)
Distorted/missing sprites	rotation-zoom ASIC / sprite RAM	Video diagnosis	Sega Y-Board
Dot crawl / crawling colours	Composite missing from the link cable → no genlock	Full cable (minus +5 V) → A/V wiring	Sega 32X
Dull RF image	Non-RGB output	RGB mod	NEC PC Engine / TurboGrafx-16
Dull RF/composite image	Non-RGB output	RGB or HDMI mod	Nintendo 64
Erratic brightness/deflection	bad electrolytics, especially the 160 V ones	Recap (160 V first)	Repair: Sanyo 20-EZ monitor
Fixed bright dot ("spot")	Spot-killer / deflection failure	⚠️ power off (phosphor burn risk), repair first	Atari — vector games (Asteroids, Tempest…)
Flicker / unstable image	dried electrolytics (recap) or the PSU (Polo)	Recap; if it persists → PSU diagnosis	Repair: Hantarex monitors
Fold-over / black bars	dead electrolytics	Recap (classic Sanwa/Sanyo symptoms)	Repair: Sanwa monitors (Sanwa Denshi)
Frozen graphics / missing blitter	Dead Special Chip (SC1/SC2)	Blitter diagnosis; community substitutes (Special Chip repro)	Williams 6809 (Defender, Robotron, Joust…)
Frozen screen / won't boot (C-2)	317-xxxx chip (protection) / customs	Check; MAME documents the protection	Sega System C / C-2
Garbage screen / won't boot	PLA or RAM dead	Substitute PLA, RAM	Commodore 64 Games System (C64GS)
Garbage screen / won't boot	PLA or RAM dead	Substitute PLA, RAM	Commodore 64
Garbled / no picture	RF / VDG / SAM	Composite mod, substitute	Dragon 32 / 64
Geometry/convergence off	OSD settings or pots	Adjust via the OSD/menu or coils/pots	Repair: modern tri-sync chassis (Wei-Ya / Makvision / Kortek)
Ghosting image	⚠️ an inherent screen defect	See the notes above	Bit Corporation Gamate
Hinge / screen (SP)	Ribbon, hinge	Replace ribbon/hinge	Game Boy Advance
Image (CRT)	tri-sync chassis, recap	Adjustments + recap	Sega NAOMI Universal Cabinet
Image (CRT)	chassis, recap	Adjustments + recap	SNK Neo-Geo cabinets (MVS)
Image shrinks / breathes / shakes	Dried-out caps (power/deflection)	Recap	Repair: Nanao MS8 monitor
Image shrinks / jitters	dried electrolytics (recap)	Recap	Repair: Nanao MS2930 / MS2931 / MS2932 / MS2933 (tri-sync)
Image shrinks / jitters	dried caps (recap)	Recap	Repair: Sanwa monitors (Sanwa Denshi)
Intermittent dropouts / flicker	cold solder joints (neck, flyback, connectors)	Reflow the hot spots	Repair: Nanao MS2930 / MS2931 / MS2932 / MS2933 (tri-sync)
Intermittent dropouts / flicker	cold solder joints (neck, flyback, deflection connectors)	Reflow the hot spots	Repair: Wells-Gardner monitors
Lines / fold	Deflection stage, caps	Recap; deflection diagnosis	Repair: Nanao MS8 monitor
Missing FMV video	No Digital Video Cartridge	Fit the MPEG cartridge	Philips CD-i
Missing lines / columns	Unstuck display ribbon	Re-flow / re-solder the ribbon	Nintendo Virtual Boy
Missing lines on the display (VA4)	Very thin wires between ribbons and motherboard broken	Extremely careful handling; see the VA4 panel box	Sega Game Gear
Missing stars (Galaga)	star-field circuit	Dedicated video diagnosis	Namco — classic hardware (Pac-Man / Galaga / Dig Dug / Xevious)
Neither image NOR power (4-port)	Automatic switchbox dead — it also carries the supply current	Switchbox bypass (remove L8 + DC jack)	Atari 5200
No / corrupt picture	ASIC / video RAM	Substitute the rest, check the ASIC	MGT SAM Coupé
No / corrupt picture	ULA / lower RAM	Cool/replace ULA, substitute 4116	Sinclair ZX Spectrum
No / garbled picture	video (VDG/GIME) / RF	Mods, substitute	Tandy TRS-80 Color Computer (CoCo)
No / unstable picture	ULA / video	Cool, substitute	Oric-1 & Oric Atmos
No 32X display	Bad connection / power	Check its own power + wiring	Sega 32X
No 3D / corrupt textures	TR3 GPU / DSP / texture RAM	Board-by-board crate diagnosis	Namco System 22 / Super System 22
No 3D / corrupt textures	custom GPU / texture RAM	Board-by-board crate diagnosis	Namco System 23 (Gorgon / Super System 23)
No 3D / freeze	one of the DSP/polygon boards, interconnects	Board-by-board crate diagnosis	Namco System 21 "Polygonizer"
No 3D, rest displays	TMS320C51 or the rendering customs	Diagnose by comparison: these chips have no replacement	Taito JC System
No digital image	DOL-101 model (no digital port)	Use a DOL-001 for the HDMI mods	Nintendo GameCube
No image	LCD panel / scaler / Lindbergh PC	Diagnose LCD; check the Lindbergh source	Sega Lindbergh (cabinets)
No image	LCD panel / scaler board / PC	LCD diagnosis; check the Type X source	Taito Vewlix
No image	Power, contacts	Diagnosis	3DO Interactive Multiplayer
No image	Power, TIA, contacts	Diagnosis	Atari 2600 (VCS)
No image	Power, contacts, switchbox	Diagnosis	Atari 5200
No image	Power, MARIA, contacts	Diagnosis	Atari 7800
No image	Power, contacts, customs	Diagnosis	Atari Jaguar
No image	Power (external block), customs	Check the dedicated PSU	Capcom CPS Changer
No image	Power, VCE, contacts	Diagnosis	NEC PC Engine / TurboGrafx-16
No image	Power, V810/video, contacts	Base diagnosis	NEC PC-FX
No image	Power, multi-out, PPU	Check power / connectors	Super Nintendo / Super Famicom (SNES / SFC)
No image	Power, VDP, multi-out	Diagnosis	Sega Master System (Mark III)
No image	Power, contacts, VDP	Diagnosis	Sega Saturn
No image	Power, VDP, RF output	Diagnosis	Sega SG-1000
No image	Power, customs, multi-out	Diagnosis	SNK Neo-Geo AES
No image	Power, contacts	Base diagnosis	SNK Neo Geo CD
No image	Power, GPU, contacts	Diagnosis	Sony PlayStation (PS1)
No image	Power, 68010, harness	Base diagnosis	Atari — arcade (System 1/2, Hard Drivin')
No image	Power, CPU, harness	Base diagnosis	Capcom — pre-CPS classics (1942, Ghosts'n Goblins, Commando)
No image	A-board (power, customs)	Check power, JAMMA contacts	Capcom CP System (CPS-1)
No image	A-board (power, custom)	Check power, JAMMA contacts	Capcom CP System II (CPS-2)
No image	Power / SH-2 / contacts	Base diagnosis	Capcom CP System III (CPS-3)
No image	Power, 68000, harness	Base diagnosis	Cave (68000 hardware)
No image	Power, bit-slice CPU, harness	Base diagnosis	Cinematronics (vector)
No image	Power, CPU, harness	Base diagnosis	Data East (DECO Cassette, DECO 8/16/32)
No image	Power, 6502, harness	Base diagnosis	Exidy (Venture, Crossbow, Mouse Trap)
No image	Power, 6502, harness	Base diagnosis	Gottlieb (Qbert, Reactor, Mad Planets)
No image	Power, V30/V33, harness	Base diagnosis	Irem M62 / M72 / M92 (R-Type & co.)
No image	Power, 68000/V70, harness	Base diagnosis	Jaleco (Mega System 1 / 32)
No image	Power, 68000/SH-2, harness	Base diagnosis	Kaneko (Kaneko 16, Super Nova System)
No image	Power, 68000, harness	Base diagnosis	Konami — 68000 beat'em ups (TMNT, Simpsons, X-Men)
No image	Power, Z80, harness	Base diagnosis	Konami — classics (Frogger, Scramble, Time Pilot, Gyruss)
No image	Power, 68000, harness	Base diagnosis	Konami Gradius / Nemesis / Twin16 (shmups)
No image	Power, 68EC020, contacts	Base diagnosis	Konami GX (System GX)
No image	Power, contacts	Base diagnosis	Midway — Y-Unit, Wolf-Unit, V-Unit, Seattle, Zeus
No image	Power, TMS34010, harness	Base diagnosis	Midway T-Unit (Mortal Kombat II, NBA Jam…)
No image	Power, Z80, harness	Base diagnosis	Namco — classic hardware (Pac-Man / Galaga / Dig Dug / Xevious)
No image	Power, 6809, harness	Base diagnosis	Namco System 1
No image	Power, R3000A, contacts	Base diagnosis	Namco System 10
No image	Power, R3000A, contacts	Base diagnosis	Namco System 11
No image	Power, COH board, contacts	Base diagnosis	Namco System 12
No image	Power, dual 68000, harness	Base diagnosis	Namco System 2
No image	Power, board interconnects	Base diagnosis	Namco System 21 "Polygonizer"
No image	Power, interconnects	Base diagnosis	Namco System 22 / Super System 22
No image	Power, CPU, harness	Base diagnosis	Nichibutsu (Crazy Climber, Moon Cresta, Terra Cresta)
No image	Power, 68020/SH-2, harness	Base diagnosis	Psikyo (68020 / SH-2)
No image	Power, 68000, harness	Base diagnosis	Raizing / Eighting (8ing)
No image	Power, SH-4/PowerVR2, contacts	Base diagnosis (NAOMI/Dreamcast-like)	Sammy Atomiswave
No image	Power, Z80, harness	Base diagnosis	Sega G80 (raster & vector)
No image	Power, VDP1/VDP2, contacts	Base diagnosis (Saturn-like)	Sega ST-V (Titan Video)
No image	Power, 68000, harness	Base diagnosis	Sega "Super Scaler" (Hang-On / Space Harrier / OutRun)
No image	Power, Z80, harness	Base diagnosis	Sega System E
No image	Power, Z80, harness	Base diagnosis	Sega System 1 / System 2
No image	Power, customs, JAMMA contacts	Base diagnosis	Sega System 16
No image	Power, V60/V70, contacts	Base diagnosis	Sega System 32
No image	Power, Z80, harness	Base diagnosis	Sega / Gremlin VIC Dual
No image	Power, dual 68000, contacts	Base diagnosis	Sega X-Board
No image	Power, CPU, harness	Base diagnosis	Seibu Kaihatsu (Raiden, SPI System)
No image	Power, CPU, harness	Base diagnosis	SNK — before the Neo-Geo (Ikari Warriors, P.O.W.)
No image	Power, 68000, harness	Base diagnosis	Taito B System
No image	Power, CPU, harness	Base diagnosis	Taito — classics (Space Invaders, Qix, Bubble Bobble…)
No image	Power, 68000, harness	Base diagnosis	Taito F2 System
No image	Power, 68020, contacts	Base diagnosis	Taito F3 System
No image	Power, CPU, harness	Base diagnosis	Tecmo (Rygar, Ninja Gaiden, Silkworm)
No image	Power, 68000, harness	Base diagnosis	Toaplan (V1 / V2)
No image	Power, Z80, harness	Base diagnosis	Universal (Mr. Do!, Space Panic, Lady Bug)
No image	Power, 6809, harness	Base diagnosis	Williams 6809 (Defender, Robotron, Joust…)
No image (HV ok)	Vector stage / joints	Diagnosis + reflow	GCE / MB Vectrex
No image (HV present)	Caps, cold joints, flyback	Recap + reflow, test flyback	Repair: Nanao MS8 monitor
No image (Noir)	LCD / PC source	LCD + source diagnosis	Namco cabinets (Noir, Exceleena, Cyberlead)
No image / corrupt 3D	i960, TGP/SHARP, video ASIC	Board-by-board diagnosis (CPU / video); rare customs	Sega Model 2
No image / corrupt 3D	Real3D (Pro-1000), PowerPC, video RAM	Board-by-board diagnosis; Real3D customs irreplaceable	Sega Model 3
No image / crash	Power, caps, contacts	Base diagnosis	Sega NAOMI
No image / crash	Power, customs, JAMMA contacts	Diagnosis (UniBIOS useful)	SNK Neo-Geo MVS
No image / no 3D	TGP (MB86233) or video ASIC, power	Diagnosis; Fujitsu customs are irreplaceable → extreme care, mind the contacts	Sega Model 1
No picture	power / harness / chassis	Diagnose power → monitor	Capcom cabinets (Mini Cute, Impress, Status)
No picture	power / harness / chassis	Diagnose power → monitor	European cabinets
No picture	power / harness / chassis	Diagnose power → monitor	Irem Madonna / Madonna 33
No picture	power / harness / chassis	Diagnose power → monitor	Jaleco — Pony cabinets
No picture	power / harness / chassis	Diagnose power → monitor	Sega Aero Table
No picture	power / harness / chassis	Diagnose power → monitor	Taito Canary
No picture	RGB SCART cable/output, or ASIC	Check the SCART cable and the TV input	Amstrad GX4000
No picture	Taos or the video output	An Apple part with no replacement	Bandai Pippin (@WORLD / ATMARK)
No picture	video stage or RF modulator	A 1982 machine: period RF output	Emerson Arcadia 2001
No picture	video crystal or the video stage	Independent of the CPU and the sound	Epoch Super Cassette Vision
No picture	RGB / PSU	Check RGB cable, recap	Fujitsu FM Towns Marty
No picture	custom video	Same crystal as the CPU	Apple Lisa
No picture	HD61K202P, or the TEA1002	⚠️ The TEA1002 is the colour encoder and video summer, not the picture generator: its failure can kill the output, but it is not the only lead. Frequency depends on the standard — see the table	Mattel Aquarius
No picture	EF9345 or its memory	See the archived schematics	Philips VG-5000
No picture	MC6847 or the modulator	Common chip, replacements findable	Sanyo PHC-25
No picture	ULA	Substitute	Sinclair ZX80 · ZX81 · QL
No picture	TMS9129 (I038) or its crystal	Crystal separate from the 8 MHz	Tatung Einstein
No picture	68000 or a crystal	⚠️ several clocks unverified — compare against a good board	Alpha Denshi / ADK
No picture	CPU, the 52 MHz video crystal, or the Tom/Jerry customs	Establish which CPU variant is fitted first	Atari Cojag
No picture	system clock or the video stage	The picture is clocked by the master crystal	Bally / Midway Astrocade
No picture	MC6809E or the C6545-1 CRTC	Both at 1.25 MHz	Bally / Sente SAC-1
No picture	68000 or the video stage	PCB diagnosis	Deniam
No picture	Z80 or its crystal	⚠️ two values coexist: 5.5 and 5.3693 MHz	Dynax
No picture	68000, 24 MHz crystal, power	PCB diagnosis	Gaelco
No picture	PSU, 6809/68000/68EC020, ADM690 watchdog	Base diagnosis	Incredible Technologies (Golden Tee)
No picture	the 48 MHz crystal or the SYSCTRL	⚠️ not the CPU's 40 MHz crystal	Jaleco Mega System 32
No picture	GCU or the VGA output	Two clocks to check: 25.175 and 16.6666 MHz	Konami Firebeat
No picture	CXD8530 / CXD8561 or power	PCB diagnosis	Konami GV (“Baby Phoenix”)
No picture	CDE2 or power	The 3DO system chip has no replacement	Konami M2
No picture	CXD8530CQ / CXD8561Q	PS1 failure modes	Konami Twinkle
No picture	Z80 or the video stage	PCB diagnosis	Bally / Midway MCR
No picture	68000 or the video stage	PCB diagnosis	Namco ND-1
No picture	JVS board or the VGA output	Video goes through the JVS board, not straight off the PS3	Namco System 357 / 369
No picture	VR4300 or the video stage	N64 failure modes	Aleck 64
No picture	PSU, RP2A03/65C816, harness	Base diagnosis	Nintendo — arcade (VS. System, PlayChoice-10, Super System)
No picture	68000 or the video crystal	⚠️ three possible crystals depending on the board	NMK 16-bit (NMK / UPL)
No picture	68000, 24 MHz crystal, power	PCB diagnosis	Playmark
No picture	PSU, 68000, JAMMA contacts	Base diagnosis	Sega System C / C-2
No picture	68000 or the 16 MHz crystal	The three main clocks are identical	Seta
No picture	PSU, VR4300, harness	Base diagnosis	SNK Hyper Neo Geo 64
No picture	ZN-2 motherboard (CXD8661R / CXD8654Q)	PCB diagnosis	Taito G-NET
No picture	Voodoo (FBI or TMU) or the VGA output	Two separate 3Dfx chips	Taito Wolf System
No picture	Z80, crystal, power	⚠️ check which board before comparing a frequency	Tecfri
No picture	HD63C09EP, 12 MHz crystal, power	PCB diagnosis	Technos Japan
No picture	68000 or the 20 MHz crystal	Both CPUs derive from it	Video System
No picture	Z80, 18.432 MHz crystal, power	PCB diagnosis	Zaccaria
No picture (Alice 32 / 90)	EF9345	Different chip, different leads	Matra & Hachette Alice
No picture (Alice)	MC6847	A chip shared with other machines	Matra & Hachette Alice
No picture (Electron)	ULA	Cool / replace	Acorn BBC Micro & Electron
No picture (G7000)	8244 / 8245, or the modulator	8244 on NTSC, 8245 on PAL: do not mix them up. ⚠️ On a G7400, see the next row	Philips Videopac G7000 and Videopac+ G7400
No picture / corrupt video	SHIFTER / RAM / GLUE	Substitute, RAM test	Atari ST (520/1040, STE, Mega, Falcon)
No picture / no HV	HOT, flyback, supply	Check HOT / flyback / +B	Repair: Hantarex monitors
No picture / no HV	HOT, flyback, +B supply	Check HOT / flyback / +B	Repair: Nanao MS2930 / MS2931 / MS2932 / MS2933 (tri-sync)
No picture / no HV	HOT, flyback, +B supply	Check HOT / flyback / +B	Repair: Sanwa monitors (Sanwa Denshi)
No picture / no HV	HOT, flyback, +B supply	Check HOT / flyback / +B	Repair: Toshiba PB-7534 (Konami Windy 2)
No picture / no HV	HOT (horizontal output transistor), flyback, +B supply	Check HOT, flyback, +B voltage	Repair: Wells-Gardner monitors
No picture / repeated blow-ups	poor-quality HOT (H output transistor) — the No. 1 fault of all tri-syncs	Replace the HOT (keep spares); find what killed it (deflection, +B)	Repair: modern tri-sync chassis (Wei-Ya / Makvision / Kortek)
No picture / wrong colours	SCART connector / video	Check the DIN cable, then the video circuit	Thomson (MO5 / MO6 / TO7 / TO8 / TO9)
No picture on a 15 kHz chassis	nothing — the board outputs 25 kHz	A medium-resolution monitor is required	Taito JC System
No picture, machine running	PVI 2636	Same chip, other function	Interton VC 4000 (and the 1292 family)
No VGA image	Non-VGA game / cable	Check the game's VGA compat	Sega Dreamcast
No video	DVD player or the serial link (CN7 or CN5)	Two distinct causes depending on the game's generation	Konami Twinkle
Nothing on screen	NAOMI / DIMM / GD-ROM	NAOMI diagnosis (see its page)	Sega NAOMI Universal Cabinet
Nothing on screen	Power, contacts, ribbons	Diagnosis	Nintendo Virtual Boy
Nothing on screen	PSU / joints / VDP	Check PSU, reflow, VDP	Sega Mark III
Odd coloured blocks in Master System games	Known VA0 board fault (twin ASIC) — fixed from the VA1	No hardware fix: it is the revision. → Revisions	Sega Game Gear
One dead screen (DualSystem / PC-10)	board or monitor of that stage	Isolate the stage	Nintendo — arcade (VS. System, PlayChoice-10, Super System)
Only locks on one frequency (e.g. 31 kHz)	tri-sync switching / sync	Check sync type (separate/composite), the frequency-detect stage	Repair: modern tri-sync chassis (Wei-Ya / Makvision / Kortek)
Only one eye displays	Ribbon / LED array on one side	Same, on the affected side	Nintendo Virtual Boy
Out-of-standard picture	impossible if the crystal is good	The scan rate is locked to NTSC	Bally / Midway Astrocade
Overvoltage / excessive HV (MTC-9000)	a capacitor goes OPEN (not shorted) → the load is "let go" → +B and HV rise (tube stress)	Recap; measure +B before reconnecting the tube	Repair: Hantarex monitors
PAL picture shifted	⚠️ unverified parameters	Compare against another PAL machine, not a published figure	Epoch Super Cassette Vision
Picture shifted or unstable	video timing (crystal ÷ 3)	Compare against the calculated figures above	Zaccaria
Picture will not lock	57.23 Hz, outside the 60 Hz window	A tolerant 15 kHz chassis, or see modernising	Sega System 18
Picture will not lock	61.31 Hz, outside the usual windows	A tolerant 15 kHz chassis, or see modernising	Video System
Poor RF image / snow	RF output	Composite/AV mod	Atari 2600 (VCS)
Screen (lines/touch)	Ribbon / panel	Replace the panel or ribbon	Nintendo DS
Screen entirely dead	cells or their contacts	Contact corrosion before anything else	Nintendo Game & Watch
Screen folded to a line / no power	analog-board caps	Analog recap	Apple Macintosh compact (128K → SE/30)
Screen kit bought turns out incompatible	VA0/VA1 kit fitted to a VA4/VA5 (or vice versa)	Identify the revision before buying → Revisions	Sega Game Gear
Screen/pixel issues	LCD panel	Panel replacement	Sony PSP (PlayStation Portable)
Segment display dead	16-segment LED or its driver	A separate item, with no effect on the game	Konami Twinkle
Shaky / unstable image	Capacitors	Recap	Sega System 16
Shaky image / bleeding colours	Monitor chassis capacitors	Recap the chassis	Sega Astro City
Shaky image / distorted vectors	Capacitors / adjustments	Recap; adjustments	GCE / MB Vectrex
Sprites no longer zoom	zoom ASIC / sprite RAM	Video diagnosis, contacts	Sega "Super Scaler" (Hang-On / Space Harrier / OutRun)
Sprites no longer zoom	zoom ASIC / sprite RAM	Video diagnosis	Sega X-Board
Sprites no longer zoom	zoom customs / sprite RAM	Video diagnosis	Taito Z System
Topper off (Cyberlead)	banner neon/LED	Replace the lighting	Namco cabinets (Noir, Exceleena, Cyberlead)
Unstable / washed-out image	CRT chassis / recap	Recap + adjustments	Capcom cabinets (Mini Cute, Impress, Status)
Unstable / washed-out image	Hantarex chassis / recap	Recap (Hantarex)	European cabinets
Unstable / washed-out image	Nanao MS8 chassis / recap	Recap + adjustments	Irem Madonna / Madonna 33
Unstable / washed-out image	CRT chassis (Nanao/Sanwa) / recap	Recap + adjustments	Jaleco — Pony cabinets
Unstable / washed-out image	Nanao MS8 chassis / recap	Recap + adjustments	Sega Aero Table
Unstable / washed-out image	Nanao or Toei chassis / recap	Identify the chassis, then recap + adjustments	Taito Canary
Unstable horizontal sync	H stage / joints	Reflow, H diagnosis	Repair: Sanyo 20-EZ monitor
Unstable image (CRT)	chassis / recap	Adjustments + recap	Namco cabinets (Noir, Exceleena, Cyberlead)
Unstable image (CRT)	tri-sync chassis, recap	Adjustments + recap (Nanao MS9)	Sega New Net City
Unstable image / colours	tri-sync chassis, recap	Adjustments + recap (Nanao MS9-like)	Konami Windy / Windy II
Unstable image / colours	Tri-sync monitor chassis, recap	Geometry adjustments + recap (Nanao MS9-like)	Taito Egret II / II Mini
Unstable image / colours	Contacts 32X↔MD, pass-through	Clean contacts, check the A/V cable	Sega 32X
Unstable image / flicker	dried electrolytics (recap)	Recap	Repair: Toshiba PB-7534 (Konami Windy 2)
Unstable image / flicker	mediocre capacitors	Recap (essential on any Makvision)	Repair: modern tri-sync chassis (Wei-Ya / Makvision / Kortek)
Unstable image / geometry	Wei-Ya M3192D chassis, recap	Adjust + recap	Sammy Atomiswave SD
Unstable image / geometry	Wei-Ya 3129D chassis, recap	Adjust + recap (see archived schematic)	Taito Egret 3
Vertical bar down the centre of the picture	voltage drop during DRAM refresh — inadequate power filtering	See below	Super Nintendo / Super Famicom (SNES / SFC)
Vertical collapse (a horizontal band) / partial collapse	vertical deflection stage/IC, its caps	Recap the vertical + check the vertical output IC	Repair: Sanyo 20-EZ monitor
Vertical/horizontal lines (DMG)	LCD ribbon (failing adhesive)	Reflow the ribbon (heat)	Game Boy / Game Boy Color
Washed-out colours / a missing colour	neck board / RGB amp, worn tube	Diagnose neck board, contacts, settings	Repair: Wells-Gardner monitors
Washed-out colours / shrinkage	G2 (screen), caps	Adjust G2; recap	Repair: Nanao MS8 monitor
Won't lock at 31 kHz	tri-sync switching / sync stage	Check incoming sync, the detect stage	Repair: Nanao MS2930 / MS2931 / MS2932 / MS2933 (tri-sync)
Won't lock at 31 kHz	tri-sync switching / sync	Check sync + detect stage	Repair: Toshiba PB-7534 (Konami Windy 2)
Won't lock at 31 kHz (29E31S)	tri-sync switching / sync	Check sync + detect stage	Repair: Sanwa monitors (Sanwa Denshi)
Wrong characters, correct colours at the faulty locations	character code RAM (ref. 667)	Signature given by the manual	Philips Videopac G7000 and Videopac+ G7400
Wrong colours	315-5313 VDP / colorizer	Video diagnosis, reseat	Sega System C / C-2
Wrong colours	misplaced overlay / colour board	Reposition the overlay / board diagnosis	Sega / Gremlin VIC Dual
Wrong colours (SI)	misplaced overlay	Reposition the overlay	Taito — classics (Space Invaders, Qix, Bubble Bobble…)
Wrong colours (VS.)	wrong RP2C0x PPU / wrong ROM-PPU pairing	Check the game's PPU variant	Nintendo — arcade (VS. System, PlayChoice-10, Super System)
Wrong colours (WG6100)	Colour stage / convergence	Adjustments, recap	Atari — vector games (Asteroids, Tempest…)
Wrong colours / priorities	CPS-B-21 setting	Custom config (see CPS-1)	Capcom CPS Changer
Wrong colours / priorities	CPS-B-21 setting	Check custom config	Capcom CP System (CPS-1)
Wrong textures or 3D	hardware — or simply a comparison against imperfect emulation	See the box above before suspecting the board	Konami M2

Power & boot (118)

Symptom	Probable cause	Next step	Page
+5 V too low / unstable	Caps, pot, harness	Recap; adjust +5 V at the JAMMA edge	Repair: Sega power block (candy cab)
2-3 minute boot	re-flash in progress — normal	Do not cut power: this is case 3 above	Taito G-NET
A first-print game refuses to run (Space Harrier, OutRun)	Console is VA10 or later (68000+SCSP merged)	It isn't the disc: see Revisions	Sega Saturn
A PAL game will not start on an NTSC unit	The NTSC BIOS's 960-bit signature lock	See Region — and the hardware remains an obstacle	Atari 7800
Batteries draining very fast	Dirty power switch	Properly clean the power switch	Game Boy / Game Boy Color
Boots into service mode	EEPROM blank or reset	A documented behaviour, not necessarily a fault	Taito Wolf System
Checkerboard at boot	lower RAM (4116)	Substitute the DRAM	Sinclair ZX Spectrum
Console dead after plugging in the mains	An Atari 8-bit brick used (AC output)	⚠️ Never a 400/800 brick on a 5200	Atari 5200
Console dies after a while	PSU over-volted the 5 V	Replace PSU; test chips	Commodore 64 Games System (C64GS)
Console dies after a while	PSU over-volted the 5 V	Replace PSU; test chips	Commodore 64
Crashes at boot	i8751 MCU (protected games)	Check the MCU; MAME dumps them	Irem M62 / M72 / M92 (R-Type & co.)
Crashes at boot	key chip / MCU	Check key/MCU; MAME emulates them	Namco System 1
Crashes at boot	protection MCU (HD63705) / sound dump	Check the MCU; MAME emulates them (community dumps)	Namco System 2
Crashes at boot	C-Chip (protected games)	Check the C-Chip; see converts	Taito B System
Crashes at boot	C-Chip (protected games)	Check the C-Chip; see converts	Taito F2 System
Crashes at boot	C-Chip (protected games)	Check the C-Chip; see converts	Taito Z System
Crashes at boot	protection MCU	Check the MCU; MAME dumps them	Toaplan (V1 / V2)
Crashes when hot	regulator overheating	Heatsinks	Tandy TRS-80 Color Computer (CoCo)
Dead / wrong-speed serial	⚠️ the CTC (I058), not necessarily the USART	See the note above	Tatung Einstein
Dead board / won't boot	Flat battery → keys lost (suicide)	Phoenix ROMs, or key reprogramming (de-suicide)	Capcom CP System II (CPS-2)
Dead FD1094 game	Flat battery (suicide)	Restore the key / decrypted ROMs; replace the battery	Sega System 16
Dead Kabuki game	Flat battery (suicide)	Phoenix ROMs, or battery replacement / re-key	Capcom CP System (CPS-1)
Dead keys	keyboard	Clean	Acorn BBC Micro & Electron
Dead keys	keyboard membrane	Replace the membrane	Amstrad CPC Plus (464 Plus / 6128 Plus)
Dead keys	keyboard membrane	Replace the membrane	Amstrad CPC (464 / 664 / 6128)
Dead keys	keyboard	Clean	Fujitsu FM-7 / FM-8 (& FM77)
Dead keys	membrane / keyboard	Clean / replace	MGT SAM Coupé
Dead keys	keyboard membrane	Replace / clean	MSX (MSX / MSX2 / MSX2+ / turbo R)
Dead keys	keyboard	Clean	Oric-1 & Oric Atmos
Dead keys	keyboard	Clean	Sharp X1 & MZ
Dead keys	keyboard membrane	Replace the membrane	Sinclair ZX Spectrum
Dead keys	membrane	Replace the membrane	Sinclair ZX80 · ZX81 · QL
Dead keys	keyboard (domes/membrane)	Clean / replace	Thomson (MO5 / MO6 / TO7 / TO8 / TO9)
Dead motherboard	ordinary PS3 failure (YLOD, power)	Replace with a donor PS3 board → conversion	Namco System 357 / 369
Dead ports	CIA 6526	Substitute the CIA(s)	Commodore 64
Dies after warm-up	7805 regulator	Replace + heatsink	Dragon 32 / 64
Fan / overheating (fat)	Dust / paste	Cleaning	Sony PlayStation 2 (PS2)
FD1094 game dead at boot	key battery gone (suicide)	Decrypted ROMs + bare 68000 → de-suicide	Sega System 18
Freeze / reboot	RAM, multi-board power, heat	Reseat, RAM test, recap, ventilation	Sega Model 3
Fried chips	killer PSU (over-volt)	Modern regulated supply	Commodore 8-bit — VIC-20 · C128 · C16/Plus4 · PET
HDD dead (Zeus/Vegas)	IDE disk on late games	Image the disk	Midway — Y-Unit, Wolf-Unit, V-Unit, Seattle, Zeus
Hot cut-outs	Cold joints, caps	Reflow + recap	Repair: Sega power block (candy cab)
Model 2 completely dead	Blown FUSE — wrong adapter, or console attached/removed while powered	Replace the fuse (an easy repair) → Model 2	Sega Mega-CD / Sega CD
Motherboard alone, nothing boots	normal — it holds no ROM	The cartridge is required	IGS PGM2
Naomi won't boot	no JVS conversion	Add a JVS I/O converter (Capcom/Sega)	Sammy Atomiswave SD
No boot / unstable	PSU (caps)	Recap PSU / modern PSU	Sharp X68000
No output / can't start	Dried-out capacitors, protection, fuse	Recap; check the fuse	Repair: Sega power block (candy cab)
No POST / beeps	RAM / card / CPU	Decode the beep codes, reseat	IBM PC & compatibles (DOS gaming)
No power	candy brick	Check +5 V at the JAMMA edge	Konami Windy / Windy II
No power	Wei-Ya P271 brick	Check 3.3 / 5 / 12 V	Sammy Atomiswave SD
No power	candy brick	Check voltages at JVS/JAMMA	Sega New Net City
No power	candy brick	Check +5 V at the JAMMA edge	Taito Egret II / II Mini
No power	Taito JVS brick	Check 3.3 / 5 / 12 V at the JAMMA/JVS edge	Taito Egret 3
No power	external power pack dead (original brick)	Test/replace the PSU (check voltage/polarity)	Amstrad GX4000
No power	battery contacts (4 × AA, 6 V)	The classic corrosion on an old handheld	Bit Corporation Gamate
No power	battery contacts, or the power socket	4 × AA or a 6 V adapter	Watara Supervision
No power LED	Brick, broken cable, tactile switch, 7805, 2200 µF cap	Diagnostic tree	Atari 7800
Noisy fan	Stock fan	Noctua + adapter	Sega Dreamcast
Nothing at power-on	Reversed centre-negative PSU → blown fuse F1	Check/replace F1; use the right PSU	Sega Mega Drive / Genesis
Nothing at power-up	monitor PSU / fuse	Check monitor→board voltage	Amstrad CPC (464 / 664 / 6128)
Nothing on power-up	monitor PSU, fuse, joints	Check monitor→board voltage	Amstrad CPC Plus (464 Plus / 6128 Plus)
Nothing powers on	mains / 100 V transformer	Check the mains input	Capcom cabinets (Mini Cute, Impress, Status)
Nothing powers up	fuse, switch, transformer, PSU input	Check fuse + mains present at the PSU	Power supplies in cabinets
Nothing starts	3.579545 MHz crystal	CPU, STIC and sound derive from it together	Mattel Intellivision
Nothing starts	19.968 MHz crystal	CPU and CTC derive from it together	Bally / Midway MCR
Overheat / reboot	PC cooling, dust	Clean, check fans	Sega Lindbergh (cabinets)
PCB burns out	+5 V too high (> 5.25 V)	Recheck the adjustment, drifting trimpot	Power supplies in cabinets
Power	PC/ATX brick + cab PSU	Check PSUs	Taito Vewlix
Power board fried after plugging in the mains adapter	Reversed polarity: US = tip positive, EU/JP = tip negative	Check the adapter — see the polarity box	Sega Game Gear
Protected game dead at boot	DS5002FP emptied (battery)	Look for an unprotected revision of the game	Gaelco
Regulator, 2 caps and 1 resistor burnt out	Wrong mains brick — no protection from the factory	Repair, then fit the 1N5400 diode	Atari Jaguar
Reset / crashes when hot	ULA / regulator	Heatsink, recap	Sinclair ZX Spectrum
Runs on mains, not on batteries	Failed DC jack (see box)	Metal contact cleaner into the jack, otherwise replace the jack	Game Boy / Game Boy Color
Slim: power	Internal PSU block	Diagnosis / replacement	Sony PlayStation 2 (PS2)
Smoke (+2A/+3)	mains RIFA	Replace the RIFA	Sinclair ZX Spectrum
Smoke / bang at power-on	mains RIFA	Replace the RIFA	Apple II (II / II+ / IIe / IIc / IIGS)
Smoke / bang at power-on	mains RIFA in the PSU	Replace the RIFA	Atari ST (520/1040, STE, Mega, Falcon)
Smoke / death at power-on	RIFA / XL/XE PSU	Replace PSU/RIFA	Atari 8-bit (400 / 800 / XL / XE)
Smoke / smell at power-on	PSU RIFA	Replace the RIFA	IBM PC & compatibles (DOS gaming)
Smoke at power-on	PSU RIFA	Replace the RIFA	Acorn Archimedes
Smoke at power-on	PSU RIFA	Replace the RIFA	Acorn BBC Micro & Electron
Smoke at power-on	PSU RIFA	Replace the RIFA	Texas Instruments TI-99/4A
Unit gets no power	monitor↔unit cable	Check conductors	Amstrad PCW (8256 / 8512 / 9512)
Unstable / dies when hot	7805 regulator	Heatsink / replace	Sinclair ZX80 · ZX81 · QL
Unstable voltages	tired output capacitors	Recap the PSU → repair	Power supplies in cabinets
Will not boot	PVI 2636 (memory select) or the S2650	The 2636 does both jobs — see the box	Interton VC 4000 (and the 1292 family)
Will not boot	CPU board or motherboard	Swap them: this platform allows it	Data East MLC
Will not boot	program CD, dongle or hard disk missing or mismatched	Check all four before the electronics	Konami Twinkle
Will not boot	cartridge contacts or the E90 board	Clean the contacts with isopropyl alcohol	Aleck 64
Will not boot	P5TX-LA motherboard — ordinary PC failure	Power, memory, CMOS battery	Taito Wolf System
Will not boot after storage	main RAM emptied	See the box	IGS011 (blitter hardware)
Will not boot, dongle missing	disk/dongle pairing broken	Without the original dongle the disk will not boot	Namco System 357 / 369
Will not power up after fitting the diode	Diode fitted the wrong way round	Reverse it (see the box)	Atari Jaguar
Will not start	μPD7801 or its 4 MHz crystal	A processor with no common replacement	Epoch Super Cassette Vision
Won't boot	internal PSU / Kickstart	Check voltages, reseat ROM	Commodore CDTV
Won't boot	M68000, 20.37504 MHz crystal, or the custom MMU	The MMU has no replacement part	Apple Lisa
Won't boot	Kickstart / RAM / customs	Check ROM, substitute RAM/customs	Commodore Amiga
Won't boot	Z80 (I001) or the X002 8 MHz crystal	Check 4 MHz after division	Tatung Einstein
Won't boot	corrupt NAND / decryption (Type-2)	Image/reflash; protection diagnosis	Namco System 10
Won't boot	missing/wrong KEYCUS, ROM board contacts	Check KEYCUS; see converts	Namco System 11
Won't boot	KEYCUS (CPLD) / flash / ROM board	Check KEYCUS; see converts	Namco System 12
Won't boot	BIOS cart / game cart / contacts	Reseat, clean connectors	SNK Hyper Neo Geo 64
Won't boot (SPI)	flash/cartridge / RISE encryption	Image the flash; protection diagnosis	Seibu Kaihatsu (Raiden, SPI System)
Won't boot / freezes	one of the two 6809 / RAM	Isolate, substitute	Fujitsu FM-7 / FM-8 (& FM77)
Won't boot / unstable	regulator / RAM / ROM	Recap, substitute	Acorn BBC Micro & Electron
Won't boot after a swap	security EEPROM not reflashed / wrong variant	See converts (PS3/4/5)	Psikyo (68020 / SH-2)
Won't power on	Power caps, contacts, fuse	Recap, contacts	Game Boy / Game Boy Color
Won't power on	Power caps / fuse / battery contacts	Power recap, check contacts	Sega Game Gear
Won't power on / shuts off	monitor/PSU board caps	Recap	Amstrad PCW (8256 / 8512 / 9512)
Won't power up	S2650 or its crystal	⚠️ 895 kHz (NTSC) or 886.6 kHz (PAL) — see the box	Emerson Arcadia 2001
Won't start	8048 or its crystal	⚠️ the value depends on the model — see the table	Philips Videopac G7000 and Videopac+ G7400
Won't start	dead printer/PSU	Repair printer / modern PSU	Coleco Adam
Won't start	M6803 or its crystal	⚠️ 3.58 MHz at the crystal, not at the core	Matra & Hachette Alice
Won't start	Z80 or the crystal	Expected: 3.58 MHz at the CPU	Mattel Aquarius
Won't start	CPU or its crystal	⚠️ 8080 or Z80 by model, three clocks	Micronique Hector
Won't start	Z80 or the 4 MHz crystal	—	Philips VG-5000
Won't start	Z80 or its 4 MHz crystal	—	Sanyo PHC-25
−5 V rail absent	−5 V stage (often the first to fail)	−5 V stage diagnosis	Repair: Sega power block (candy cab)

Chips, RAM & customs (12)

Symptom	Probable cause	Next step	Page
CPU “too slow”	nothing — ~895 kHz is the normal value	See the box	Mattel Intellivision
Erratic behaviour	R3041 or 68EC020, board depending	Two platforms in one: do not compare measurements across variants	Atari Cojag
Erratic behaviour	one of the two PowerPC 602s	Measure both	Konami M2
Erratic behaviour	H8/3002 or its code on the board	The MCU has no internal ROM: the code reads off the board	Namco ND-1
Erratic behaviour	dead/missing COP (co-proc)	COP diagnosis; MAME emulates it	Seibu Kaihatsu (Raiden, SPI System)
Erratic behaviour	the daughterboard's MC68HC11M0	The MCU lives on the game board, not the motherboard	Taito JC System
Erratic behaviour	the second processor	Check which is fitted: 6309 at 1.5 MHz or Z80 at 4 MHz	Technos Japan
Erratic timer behaviour	one of the Z80 CTCs	Two of them on the sound board	Bally / Sente SAC-1
Memory corruption	4116 DRAM	Test / replace	Dragon 32 / 64
Memory corruption	DRAM	Test / replace	Tandy TRS-80 Color Computer (CoCo)
Memory corruption	DRAM	Test / substitute	Tandy TRS-80 Model I / III / 4
Z80 “at 2.5 MHz”	nothing — that is the normal value	See the box	Bally / Midway MCR

Instability & intermittent faults (37)

Symptom	Probable cause	Next step	Page
Corrosion (IIGS)	leaked battery	Remove, repair traces	Apple II (II / II+ / IIe / IIc / IIGS)
Corrosion on the motherboard	PRAM battery leaked	Take the battery out before any diagnosis	Bandai Pippin (@WORLD / ATMARK)
Crash / freeze	RAM, power, multi-board interconnects	Reseat, RAM test, targeted recap	Sega Model 2
Crashes when the machine is moved	RAM pack wobble	Clean/brace the connector	Sinclair ZX80 · ZX81 · QL
Flaky switches	Worn switches	Clean / replace	Atari 2600 (VCS)
Freeze (Twin16)	one of the 2× 68000	CPU diagnosis, RAM test	Konami Gradius / Nemesis / Twin16 (shmups)
Instability	PSU/board caps	Recap	Fujitsu FM Towns Marty
Instability	caps	Recap	Coleco Adam
Instability	caps	Recap	Dragon 32 / 64
Instability	caps	Recap	Fujitsu FM-7 / FM-8 (& FM77)
Instability	caps	Recap	MGT SAM Coupé
Instability	caps	Recap	Oric-1 & Oric Atmos
Instability	caps	Recap	Sharp X1 & MZ
Instability	caps	Recap	Tandy TRS-80 Color Computer (CoCo)
Instability	PSU caps	Recap	Texas Instruments TI-99/4A
Instability / bounce (Model I)	grounds / Expansion Interface	Joints, contacts	Tandy TRS-80 Model I / III / 4
Instability / crashes	PSU/board caps	Recap	Acorn Archimedes
Instability / crashes	PSU (caps) / RAM	Recap PSU, substitute RAM	Apple II (II / II+ / IIe / IIc / IIGS)
Instability / crashes	tired PSU/board caps	Recap	Atari ST (520/1040, STE, Mega, Falcon)
Instability / crashes	PSU/board caps	Recap	Fujitsu FM Towns (& FM Towns Marty)
Instability / crashes	PSU/board caps	Recap	MSX (MSX / MSX2 / MSX2+ / turbo R)
Instability / crashes	PSU/board caps	Recap	NEC PC-8801 (PC-88) & PC-9801 (PC-98)
Instability / crashes	PSU/board caps	Recap	Thomson (MO5 / MO6 / TO7 / TO8 / TO9)
Instability on Model 2 VA2.3 / VA4	Known incompatibility, no documented fix	Workaround: play from a flash cart	Sega 32X
Intermittent contacts / in-game crashes	Cartridge port pins (fragile on the Jaguar)	Cleaning, inspect the pins	Atari Jaguar
Intermittent cut-outs	Cold joints (flyback, deflection, connectors)	Reflow the suspect points	Repair: Nanao MS8 monitor
Intermittent dropouts	cold solder joints	Reflow	Repair: Hantarex monitors
Intermittent dropouts	cold solder joints	Reflow	Repair: Sanwa monitors (Sanwa Denshi)
Intermittent dropouts	cold solder joints	Reflow	Repair: Toshiba PB-7534 (Konami Windy 2)
Intermittent dropouts	factory lead-free solder (cracked joints)	Reflow and re-tin with 60/40 on every joint	Repair: modern tri-sync chassis (Wei-Ya / Makvision / Kortek)
Intermittent dropouts / instability	board cracks (the 20-EZ PCB cracks easily — hairline cracks across traces)	Inspect under magnification, repair cut traces	Repair: Sanyo 20-EZ monitor
Random freeze	dual 68000 / shared RAM	CPU diagnosis, RAM test	Namco System 21 "Polygonizer"
Random freeze	68EC020 / DSP / shared RAM	CPU diagnosis, RAM test	Namco System 22 / Super System 22
Random freeze	R4650 / shared RAM	CPU diagnosis, RAM test	Namco System 23 (Gorgon / Super System 23)
Random freeze	one of the 3× 68000 / shared RAM	Per-CPU diagnosis, RAM test	Sega Y-Board
Random Guru Meditation	RAM / caps / joints	RAM test, recap, reflow	Commodore Amiga
Visible corrosion	Cap leak	Neutralise, recap, jumper the traces	PC Engine CD-ROM² / Duo

Mechanical & cosmetic (7)

Symptom	Probable cause	Next step	Page
Broken hinge (DS Lite)	Fragile shell/hinge	Replace shell/hinge	Nintendo DS
Monitor rotation stuck	rotation mechanism	Check/grease the rotating frame	Taito Egret II / II Mini
Stiff / crooked rotation	manual rotation frame	Check/grease the frame, realign the bezel	Taito Egret 3
Yellowed plastic	UV	Retrobright	Nintendo 64
Yellowed plastic	UV / ABS	Retrobright (with care)	Super Nintendo / Super Famicom (SNES / SFC)
Yellowed plastic	UV / ABS	Retrobright	Sega Master System (Mark III)
Yellowed plastic	UV / ABS	Retrobright	Sega SG-1000

Network & link (1)

Symptom	Probable cause	Next step	Page
Stuck on network check	link between cabinets (linked games)	Check CN4/CN5 and the game's configuration	Konami Viper

❓ Not yet sorted (28)

These lines do not match any keyword family yet. They are listed rather than dropped: an index that hides what it could not sort is an index one trusts wrongly.

Symptom	Probable cause	Page
"Abnormal" slowdown	(often deliberate — danmaku)	Cave (68000 hardware)
"Warming up" never finishes	dead bubble memory (Bubble System)	Konami Gradius / Nemesis / Twin16 (shmups)
Activision Decathlon, Robot Tank or Space Shuttle (2600) misbehaving	Timing circuit on the C025233-002 board	Atari 7800
K-Razy Shoot-Out, Mountain King or Pitfall! will not run	BIOS C019156A on some late 2-port units	Atari 5200
All normal except the special scenery characters	extension RAM (ref. 671)	Philips Videopac G7000 and Videopac+ G7400
B+ stuck low (e.g. ~30 V)	regulation / supply	Repair: Sanyo 20-EZ monitor
Boss that never times out	MCU (timing)	Alpha Denshi / ADK
Card not detected	slot contacts	Apple II (II / II+ / IIe / IIc / IIGS)
Card not detected	ISA contacts	IBM PC & compatibles (DOS gaming)
Coins not counted	TC0510NIO or wiring	Taito Wolf System
Corrupted characters	character generator ROM (4 KB)	Sanyo PHC-25
Crystal “at 16 MHz” where the board says 8	nothing — the silkscreen is wrong	Seta
CX55 adapter does not work	4-port cartridge port not wired for the CX55	Atari 5200
Danmaku slowdown	(often deliberate)	Raizing / Eighting (8ing)
Frozen menu (PC-10 / NSS)	Z80 BIOS / menu ROM / cart contacts	Nintendo — arcade (VS. System, PlayChoice-10, Super System)
Incoherent game behaviour	Alpha MCU	Alpha Denshi / ADK
Inconsistent timer	mis-set DIPs	Nintendo — arcade (VS. System, PlayChoice-10, Super System)
Missing or faint segments	glass/board contact (zebra strip)	Nintendo Game & Watch
No 80-col mode (C128)	VDC / video RAM	Commodore 8-bit — VIC-20 · C128 · C16/Plus4 · PET
No effects	OKI M6295	Deniam
Nothing responds	oxidised button contacts	Nintendo Game & Watch
The 12 extra keys do not respond	⚠️ may be normal	Philips Videopac G7000 and Videopac+ G7400
Unstable game	Cartridge port contacts	Sega 32X
VIA "out of spec" at 1.27 MHz	nothing on a 2/10 or a Mac XL	Apple Lisa
Wrong stopwatches (Gold Medalist)	MCU (interrupts)	Alpha Denshi / ADK
“25C MBAD” error	CD and EEPROM mismatched	Konami GV (“Baby Phoenix”)
“SYSTEM ERROR” under the G NET logo	no cart detected	Taito G-NET
“Unknown” chip on the board	nothing — see “ENC EL1200AR” above	Technos Japan

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