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Repair: Nanao MS9 monitor

The successor to the Nanao MS8, fitted in more recent Sega candy cabs (New Astro City, Blast City, Net City…). Same repair philosophy: recap first.

Identification

Field Value
Manufacturer Nanao (EIZO)
Type Colour CRT monitor chassis
Sizes MS9-29 (29") and variants
Frequencies 15 / 24 kHz; tri-sync variants (15/24/31 kHz) exist
Cabinets New Astro City, Blast City, Net City…

Differences from the MS8

  • A more recent chassis (New Astro City 1995 and later).
  • Some variants handle 31 kHz (VGA/Naomi) — to confirm per the exact sub-model. The true Nanao 15/24/31 kHz tri-sync is the MS2930–MS2933 series (New Net City, Naomi Universal).
  • Identical repair procedure: see the Nanao MS8 page for the detail (tube discharge, recap, reflow, adjustments).

Level & risks
Difficulty Intermediate → Advanced
Risks CRT high voltage (lethal), fragile joints
Time Recap: 2-4 h

High voltage — discharge the tube

Like any CRT: high voltage retained even unplugged. Discharge the anode before work. Don't work alone if untrained.

Common faults

Identical to the MS8: image that shrinks/shakes, no image, focus, washed-out colours, intermittent cut-outs (cold joints), deflection folds. → Detailed table on the Nanao MS8 page.

Procedure — working through a chassis ✅

Discharge the anode before anything else

The tube holds its charge with the cabinet unplugged, and so does the main filter capacitor. Discharge it, keep one hand in your pocket, and do not work on it alone. → CRT safety

Hot chassis: the ground is not earth

Some arcade chassis are referenced to the mains. On those, chassis ground is not earth, and an earthed oscilloscope clipped to it makes a dead short through your probe. Work through an isolation transformer. → CRT safety

1. Cold, before switching on. Cracked solder joints are the fault on these chassis — around the connectors, the flyback and anything heavy enough to work its own joints loose. Also swollen capacitors, cooked resistors, the brown halo of something that has been running hot. Reflow what looks suspect before diagnosing: a good share of intermittent chassis faults end there.

2. Fuse and primary side. A fuse that goes again is a short downstream, not a fuse problem — find it before fitting another.

3. Is there EHT at all? The tick of the flyback at switch-on, the filament glowing in the neck. No EHT points at the supply or the line stage. EHT but no picture points at video or the G2 — two very different jobs, and this is the measurement that separates them.

4. Recap — before any adjustment. This page carries the capacitor list — take the one matching your exact chassis if it covers more than one. On a chassis of this age recap is not optional: the electrolytics are thirty years old and have been running hot since day one. → Recap

5. Adjustments, and only now. ⚠️ Never before the recap. Setting the geometry of a chassis whose capacitors are dying records the drift and makes you do the whole job twice. Write down where every pot was before you touch it. → CRT safety

6. Scan rate. This page gives: 15 / 24 kHz; tri-sync variants (15/24/31 kHz) exist. A board whose rate is not one of these shows nothing, and nothing is faulty — check that before you suspect the chassis.

7. Verification. Let it run warm for a good while and check the geometry stops moving. A chassis that is right cold and wrong after twenty minutes is still a thermal fault — usually a joint, sometimes a capacitor you left in.

Recap

The main repair. Identical procedure to the MS8: see the MS8 recap section.

Capacitor list — MS-9 ✅

Source: Arcade Otaku (reference listing). 40 capacitors, including a bipolar C411 (2.2 µF/50 V). The C911 1000 µF/200 V filter is separate (mentioned by seller kits, not counted here). Shopping list:

Value Voltage Qty
1 µF 50 V 3
2.2 µF 50 V 4 (incl. 1 bipolar, C411)
10 µF 16 V 1
10 µF 35 V 1
10 µF 50 V 3
10 µF 250 V 2
22 µF 50 V 5
47 µF 16 V 5
47 µF 160 V 1
100 µF 10 V 1
100 µF 16 V 1
100 µF 35 V 4
100 µF 160 V 1
180 µF 25 V 1
180 µF 100 V 1
220 µF 100 V 1
470 µF 16 V 2
680 µF 10 V 1
680 µF 35 V 1
1000 µF 35 V 1

Seller discrepancies

Some seller kits list slightly different values on a few references (e.g. C406, C562, C955) and a total around 42. Cross-check with your board / the schematic if in doubt.

Per-reference list (40) — expand

NB = neck board, RB = remote board, BP = bipolar.

Ref µF V Ref µF V
C102 1 50 C455 10 50
C107 22 50 C456 10 50
C201 47 16 C457 10 50
C202 47 16 C458 22 50
C203 47 16 C459 22 50
C211 2.2 50 C503 100 35
C212 2.2 50 C513 10 250
C213 2.2 50 C515 100 160
C220 470 16 C554 1 50
C221 100 16 C556 1 50
C222 22 50 C561 47 16
C280 (RB) 10 16 C562 100 10
C332 (NB) 10 250 C951 180 100
C402 470 16 C952 220 100
C406 1000 35 C953 47 160
C407 100 35 C954 680 35
C408 100 35 C955 180 25
C409 100 35 C956 680 10
C411 (BP) 2.2 50 C957 10 35
C451 22 50 C958 47 16

→ Alternative kits: Console5 · arcademonitor.com

The values, surveyed board by board ✅

ⓘ MS9-29 — this wiki now carries cap maps: location by location, the value and the voltage as a contributor read them off their own board. → MS9-29

⚠️ This is not a manufacturer specification. A revision changes the list: read the can before you pull it, and where it disagrees with your board, your board is right. ⓘ A voltage the sheet does not give shows as —, never as a plausible number.

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.