Repair: Nanao MS2930 / MS2931 / MS2932 / MS2933 (tri-sync)¶
The Nanao tri-sync family — the 31 kHz big brothers of the MS8/MS9. These 29" chassis accept 15 / 24 / 31 kHz (where MS8/MS9 stop at 15/24 kHz), hence their use in late tri-sync candy cabs (New Net City, Naomi Universal…). Repair is identical to MS8/MS9: recap, reflow, HOT/flyback.
Identification / family¶
| Chassis | Sync | Note | Compatibility |
|---|---|---|---|
| MS2930 | 15/24/31 kHz | 29" | ↔ MS2931 / MS2934 (compatible) |
| MS2931 | 15/24/31 kHz | 29", Toshiba tube | ↔ MS2930 / MS2934 |
| MS2932 | 15/24/31 kHz | 29", A68KJU96X tube (= MS9-29 / MS8-29 / D29CR55) | tube shared with MS8/MS9 |
| MS2933 | 15/24/31 kHz | 29" | = "bug-fixed" MS2931 |
| MS2934 | 15/24/31 kHz | 29" | ↔ MS2930 / MS2931 |
- vs MS8 / MS9: the MS8 and MS9 are 15/24 kHz; the MS29xx series adds 31 kHz (VGA / Naomi / Type X). The tube is the same Toshiba A68KJU96X as MS8-29/MS9-29 (handy for a tube donor).
Safety (read first)¶
High voltage — discharge the tube
Lethal high voltage held while unplugged → discharge the anode. See CRT safety & HV discharge. Isolation transformer for powered measurements.
Common faults¶
Identical to MS8/MS9 (same component families):
| Symptom | Likely cause | Lead |
|---|---|---|
| No picture / no HV | HOT, flyback, +B supply | Check HOT / flyback / +B |
| Intermittent dropouts / flicker | cold solder joints (neck, flyback, connectors) | Reflow the hot spots |
| Image shrinks / jitters | dried electrolytics (recap) | Recap |
| Won't lock at 31 kHz | tri-sync switching / sync stage | Check incoming sync, the detect stage |
| Blur / washed-out colours | flyback focus / neck board | Adjust focus, diagnose the neck board |
Repair (method)¶
- HV discharge → CRT safety.
- Recap (method) — same procedure as MS8/MS9; cross-check the BOM against your board (revisions), the big filter is often outside the kit.
- Reflow the joints (neck, flyback, deflection connectors, neck board).
- HOT / flyback = wear; focus / screen (G2) on the flyback, geometry.
- Tri-sync: if 31 kHz won't lock, check the sync type and the frequency-detect stage.
Equivalents (chassis swap)¶
Per Arcade Otaku: MS8/MS9 ≈ Rodotron 666a / Wei-Ya 2931a / Neotec 2702; the MS2932 ≈ Rodotron 666b1 (untested against MS2930/MS2931). A beyond-repair chassis can be replaced by an equivalent — check tube/yoke and frequencies.
Cap kits & parts¶
- Nanao MS9-29 cap kits (close) and Nanao flybacks from arcade vendors; read off your board for the exact MS29xx series.
See also¶
- Nanao MS8 · Nanao MS9 (15/24 kHz, detailed BOM) · Sanwa · Modern tri-sync · CRT safety · Recap.
Sources & attribution¶
- Arcade Otaku Wiki — Nanao MS-2931 & Monitor Chassis Equivalents (MS29xx family, tubes, equivalents) — https://wiki.arcadeotaku.com/w/Nanao_MS-2931
- Arcade-Projects — MS2932/MS2933 (compatibility, A68KJU96X tube, MS2933 = fixed MS2931) — https://www.arcade-projects.com/threads/monitor-chassis-nanao-ms2933.9732/
- mikejmoffitt.com — Nanao MS9-29 information (yokes, tubes) — https://mikejmoffitt.com/pages/ms9-hax/index.html
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.
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