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NEC PC-8801 (PC-88) & PC-9801 (PC-98)

The standards of Japanese computing. The PC-88 (Z80) is the machine of Japanese RPG/AVG (Ys, Hydlide, Thexder); the PC-98 (x86) dominated Japan (business and games — eroge, and the first Touhou!). Two distinct lines, same maker. Standard period-micro repair: recap, floppies, battery.

NEC PC-9801 RX

NEC PC-9801 RX — photo by htomari, CC BY 2.0 (Wikimedia Commons).

Identification / lines

Line Key models Year CPU Note
PC-8801 (PC-88) mkII SR / FR / MR / FH / MH / FA / MA 1981-85+ Z80 @ 4-8 MHz JP RPG/AVG; FM YM2203 (OPN) → YM2608 (OPNA) sound
PC-9801 (PC-98) 9801 → VM/VX/RA/DA/BX/9821… 1982+ 8086 → V30/286/386/486 JP-dominant; GDC µPD7220; FM YM2203/2608
PC-6001 / PC-8001 — 1979-81 Z80/µPD780 NEC's beginnings

(The PC Engine console is another NEC branch.)

Repair (technician)

  • Recap: PSU and board electrolytics (the No. 1 instability source on these period machines) → Recap.
  • Battery (RTC/CMOS) — especially the PC-98: a leaking battery → remove/replace, repair traces → backup batteries.
  • Floppy drives (5.25″ then 3.5″): tired mechanism → Gotek/emulator; the PC-98 uses a particular 1.2 MB format.
  • GDC (µPD7220) / graphics: corrupt video = VRAM + GDC → substitution.
  • FM sound: YM2203/YM2608 (a sound card on some 98s) — sound-stage diagnosis.
  • Video output: analog RGB (24/31 kHz per model) → a suitable monitor / mods.

Procedure — a dead computer, step by step ✅

What this adds

Ordered for a home computer: what kills these is its power supply, its battery, its capacitors, its socketed RAM and its keyboard — roughly in that order, and well before the CPU. → PCB diagnosis

1. The power supply — measured before it is plugged in. This is the one step not to swap around. On a machine of this age a supply does not simply stop: a 5 V regulator that fails high puts 7, 9, 12 V onto the bus and takes the RAM and the custom chips with it. Measure every rail off the machine, under a dummy load if you can, and only then plug it in.

2. The battery — before anything else. This page documents a cell that leaks — check on the page whether your model is one of the affected ones, several of these pages cover a whole range. Its electrolyte eats the copper underneath and keeps eating while the machine sits in a cupboard, so it comes out first, before any diagnosis. Neutralise, clean, then check continuity on the tracks around it — a machine that no longer boots after storage is very often this and nothing else. → Backup batteries

3. Capacitors. Recap is the default on these machines, not a last resort — and on the supply first, since that is what protects everything else. → Recap

4. RAM, on its sockets. These machines were built to be repaired: the RAM, and often the logic, sit in sockets. Reseat everything first — thirty years of oxide is a classic no-boot. Then swap chips: a bad RAM chip usually gives a repeatable pattern of garbage or a screen frozen at a fixed character.

5. The keyboard. A console does not have one; a computer's is a wear part. A membrane keyboard fails as whole dead rows or columns — that is the membrane, not the machine. A mechanical one wants its contacts cleaning, not replacing. Check this page: the failure mode is often documented per model.

6. Storage — tape or disk. Both often come down to the same things: a dirty head, and for tape the azimuth and a belt turned to tar. ⚠️ On the floppy side, check whether the mechanism actually has a belt before looking for one: many do, but some drives are direct drive, and hunting a belt that isn't there means stripping a drive for nothing. A machine that boots but loads nothing is a drive fault, not a logic fault — do not go looking on the board for it.

7. Video output. RF, composite, RGB or a dedicated monitor, depending on the machine (see Identification). Test with something else before you conclude: a period modulator and a modern TV disagree far more often than either is broken.

8. Still nothing. Now the logic: rails on the board, reset, clock, bus. → PCB diagnosis

Common faults

Symptom Likely cause Lead
Instability / crashes PSU/board caps Recap
Corrosion / wrong clock (98) leaked CMOS battery Remove, repair traces
Floppy not read mechanism / format Clean, Gotek
Corrupt video VRAM / GDC Substitute VRAM, test GDC
Silent sound YM2203/2608 Sound-stage diagnosis

Modernisation & mods — what to buy, how

Leaking CMOS/RTC battery + recap

PC-98: the CMOS/RTC battery leaks and eats the board → remove it, repair traces, replace with lithium + diode. Recap board/PSU; change drive belts (unreadable disks); clean contacts.

Modern storage - PC-98: SCSI → BlueSCSI / SCSI2SD 🟢 (many PC-98 are SCSI), CF on IDE (later models) 🟢; floppy → Gotek + FlashFloppy or HxC (2HD/2DD) 🟡. PC-88: Gotek/SD 🟡.

Video - Analog RGB 24/31 kHz output (PC-98) 🟢 → OSSC / RetroTINK or RGB2HDMI; connector adapters per model.

⚠️ Do not host ROMs/games — method only.

See also

Sources & attribution

Review & corrections

How this space is used

Spotted a wrong value, an outdated procedure, a chip reference that does not match your board? Say so here, with what you observed (model, board revision, serial number, measurement). Every report is cross-checked against a source before anything changes — an unverifiable correction is published as “reported by …, not cross-checked” rather than silently applied.

Reading is open to everyone; posting requires signing in with Discord. Reports from the wiki's declared reviewers are handled first; anyone else's are read too, but go through a human before anything is changed.