Skip to content

Repair: modern tri-sync chassis (Wei-Ya / Makvision / Kortek)

Modern tri-sync CRT chassis — Wei-Ya & Makvision (Taiwan, often the same chassis rebadged, e.g. M3129) and Kortek (Korea) — are the universal CRTs of late candy cabs, bartops and replacements. They auto-switch 15 / 24 / 31 kHz (VGA D-sub input) → perfect for mixing 15 kHz games and Naomi/Type X (31 kHz). The catch: average build quality (fragile HOT and capacitors, lead-free solder to redo).

Identification / range

Brand Chassis (e.g.) Sizes Frequencies Input
Wei-Ya / Makvision M3129 (M3129DF/DB…), 3125B, M2929… 14" → 29" 15 / 24 / 31 kHz auto VGA HD-15 (analog + TTL), separate/composite sync
Kortek tri-sync CRT chassis + arcade LCD panels 15" → 29" 15/24/31 kHz (CRT) VGA

M3129 specs: CGA/EGA/VGA auto, 640×480 max, 47-70 Hz vertical, ~65 MHz bandwidth, 100-240 V AC, ~120 W, 15-pin D-sub.

Safety (read first)

High voltage — discharge the tube

Lethal high voltage held while unplugged → discharge the anode before work. See CRT safety & HV discharge. Isolation transformer for powered measurements.

Common faults

Symptom Likely cause Lead
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)
Unstable image / flicker mediocre capacitors Recap (essential on any Makvision)
Intermittent dropouts factory lead-free solder (cracked joints) Reflow and re-tin with 60/40 on every joint
Only locks on one frequency (e.g. 31 kHz) tri-sync switching / sync Check sync type (separate/composite), the frequency-detect stage
Geometry/convergence off OSD settings or pots Adjust via the OSD/menu or coils/pots

Repair (method)

  1. HV discharge → CRT safety.
  2. HOT: the structural weakness. On a blow-up, fit a quality HOT (a robust equivalent) and find the cause (deflection, +B, driver) before powering up — or it blows again.
  3. Recap (method): the factory caps are mediocre → a cap kit is recommended on any Makvision/Wei-Ya.
  4. Redo ALL joints: these chassis use problematic lead-free solder → reflow + add 60/40 (frequent cold joints).
  5. Adjustments: auto frequency (check the incoming sync), geometry via OSD/pots.

Upside (preservation)

  • 15/24/31 kHz tri-sync + VGA input: one CRT for classic 15 kHz and 31 kHz (Naomi, Type X, arcade PC). A CRT option when an original chassis (Nanao/WG) is beyond repair.

Cap kits & parts

  • Makvision cap kits (generic arcade vendors); spare HOTs (keep stock).
  • ⚠️ Cross-check against your board: several revisions/sizes.

See also

Sources & attribution

  • forum.arcadecontrols.com / Arcade-Museum — Wei-Ya/Makvision M3129 & 3125B chassis (weak HOT, recap, lead-free solder, tri-frequency sync) — https://forum.arcadecontrols.com/index.php?topic=166359.0
  • Makvision M3129 product data (15/24/31 kHz, 640×480, VGA) — spec cross-check
  • Wei-Ya / Makvision / Kortek — service manuals — to reference

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.