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RandomRetro

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Recently picked up a MVS U4 which has a Toei TC-HV25LMK chassis. I haven't worked on one of these chassis before, and frankly can hardly find anything online about it so wanted to start a thread to post what I see and find.

Initial Findings:
  • Lots of adjustment pots, but in hard spot to reach.
  • PCC.Adj (A) and PCC.Adj (B) are on a daughter board; currently not effecting anything though for me.
  • Tons of jumper wires on this thing.
  • Flyback is a pain to adjust when monitor is mounted in the cab.
  • Flyback, top pot is focus, and bottom pot is screen/brightness.
  • CN401/CN402 = Low 15khz / Med 24khz Resolution.
  • Recap kit available from Arcade Parts & Repairs.
Questions:
  • H.Coil and PCC adjustments aren't doing anything; wondering if something is needing a swap in the Horizontal circuit?
  • There is no degauss button connection. I think the degauss for other Toei chassis is J1, but on this chassis it is shorted. Is this chassis auto-degauss?
  • There is a loose ground jumper off the main board, is that supposed to go somewhere or just a spare?
Chassis Pic (Online pic which shows J1 wired in - white wires on left running off the board):
E63E6E5E-7C46-40DC-8039-112EA182E15C.jpeg

Resolution Jumper Pic:
2C30DA04-5923-4E09-A41A-4A9C9E992089.jpeg

PCC Adj pots Pic:
6E059E0A-1BA3-4744-8C9F-7F1B7BD07413.jpeg

Degaussing Jumper (J1) Pic:
087066EA-8703-4B94-808E-97EDBC85CBE8.jpeg

Flyback Pics (top focus, bottom screen):
7EAD93A6-F0A5-4C8D-96A7-61E90777B29E.jpeg
 
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dos

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Honestly I am going to use this thing until it dies and then replace the chassis with a MS8 or MS9, which is apparently easily done. For now it works, just sometimes flickers/temporary vertical collapse on a cold start, and it buzzes constantly. The picture is amazing other than a faint blue glow on the left during bright white screens, not sure what that's about.
 

Razo

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Good luck with your repair work. I used to own a MVU and IMO the Toei is the best crt monitor I ever played on
 

dos

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Yeah it is really excellent, it's just a shame they're fragile and replacement flybacks are impossible to find.
 

AlxUnderBase

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Nice theard ! From all U4 25" , that goes out to new owners with Toei chassis + toshiba tube and 1 x U4 equiped with toei + hitachi tube !
All i know is Toei comes from factory in majority of U4 25" cabinets
Looks like my flyback may be toast as well. And nope not sure there are good flyback options online. Likely need to find one off a donor chassis.
I will try to help with an working Toei chassis . Let me know if you still need it :happy:

J1 is 110 , it doest to be shorted
 
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RandomRetro

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Honestly I am going to use this thing until it dies and then replace the chassis with a MS8 or MS9, which is apparently easily done. For now it works, just sometimes flickers/temporary vertical collapse on a cold start, and it buzzes constantly. The picture is amazing other than a faint blue glow on the left during bright white screens, not sure what that's about.
Haven’t looked into a chassis swap yet, but if the Toshiba tube can handle a MS8 or MS9 chassis that would be an interesting option. Is there any thread discussing this?
 

dos

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RandomRetro

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So I was told a Toei TC-A252S should be swappable on my tube. But trying to find someone that can confirm this is a compatible swap with the Toei TC-HV25LMK. Anyone know?
 
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