Need help reparing Wei-Ya C2929 Chassis

[dasbuttonmasher]

Hey folks,
I'm brand new here, hope you don't mind me asking for some assistance.

I only recently got my first cab and it has a MAK/Wei-Ya C2929 chassis. I was having a good time with it until I suddenly lost horizontal and pin cushion control. The HOT is testing bad, seems to be a short. I figured I'd order a cap kit while I was at it so I purchased a C2929D kit which I now understand is a very different chassis.

1. Does anybody know where I can find the C2929 schematics? I'm not terribly good at finding things but I have certainly tried. If you have it I would greatly appreciate it!
2. Why do you think the HOT died? My flyback seems to be working just fine, I've not noticed any naughty behavior there. Is it possible it just gave up on life or do you think it was damaged by something nearby?

Appreciate any help with this!

[grantspain]

is it this chassis

makvision-schem49-2717-00D2rev.pdf

I doubt the hot is short otherwise chassis would not run, no horizontal size or pin control?

[dasbuttonmasher]

Thank you for posting those schematics but those are for the C2929D which is similar but quite different. The 2929 is 15-31KHz while the 2929D is 30-50KHz.

The transistor in question is a 2SC5144 NPN - I ordered a replacement that should be here tomorrow. I'm going to pull it and I'll test them side by side to determine if its bad or not. Yes, I lost horizontal and pin control. I'm in the process of recapping now but please let me know if there's anything else I should check out.

[grantspain]

show me a photo of your chassis

[dasbuttonmasher]

Sure thing, I guess I should have started with this. There are no markings or stickers on the chassis that I can find so I identified it with pictures and matching frequencies, meaning I could be wrong.

BTW, I took the transistor out and measured .45V from B-E and .52V from B-C. The new one should be here later today so I'll have a chance to verify those values are bad. It is low and I'm hoping this can explain why I get picture but lose control.

I've only pulled about a dozen caps so far but each one has tested good ESR and are reading correct capacitance. I'm getting a little discouraged that recapping will accomplishing much of anything.

Sorry for the searing pink, I setup at my daughter's homework desk lol

https://photos.app.goo.gl/P3urzRyLqHx3W4Qr7
https://photos.app.goo.gl/VFXxeeLJCpySawSv9

[grantspain]

i have never seen that chassis, is looks like a hybrid digital version on the 3129

do you have a bdx53 transistor on that chassis anywhere, it would be bolted to the heatshield

[dasbuttonmasher]

I don't see one labeled as such. There are 2 on the primary heatsink, I think they are both TAO8172 but one is directly behind the flyback and I cant see very well.

The new transistor measured the same as the old. I put everything back in the cab and I get no start on the chassis - I can hear a clicking like a relay shutting it down.

Well, don't know if I borked it or if it was on its way out anyway and I just haven't found the problem yet. Pretty discouraged and feeling like a dope.

[grantspain]

it was never going to be the HOT as if they short the chassis will never start, you need to check your soldering as the pads are delicate and i hope you used standard heatsink compound and not the metallic type used on pc heatsinks
the tda8172 is the vertical deflection ic
is the picture far too wide or too narrow?

[dasbuttonmasher]

There is pad for the heatsink so I didn't change that. I've triple checked everything. When it was starting up, it was too wide. Do you think it could be the flyback that's actually failing?

[grantspain]

could be flyback, the es31 flyback do same thing
otherwise it could be a hv cap gone out of spec or even short

you could always try dummy loading the collector pad of the HOT with a mains lamp(isolate HOT from circuit to do this), that way you can prove voltages and possibly rule out flyback

[siddhartha]

I have a rebranded 2929 as a Billabs BL27CB0P that I also need help repairing. In 15kHz mode there are significant horizontal linearity issues. The right side of the screen gets very compressed at the edge.

I've read about replacing the 0.56uF S-correction cap on a similar Betson that might fix the issue:
https://forum.arcadecontrols.com/index. ... msg1335285

On a similar Rodotron, the S-correction cap can be increased from 0.43uF to 1.0uF to fix the issue:
https://wiki.arcadeotaku.com/w/Rodotron ... n_in_15KHz

There is a 30-50kHz Makvision that uses the same board, but there are some caps not populated:
https://forum.arcadecontrols.com/index. ... 003.0.html

This is a picture of my board:
https://drive.google.com/drive/u/0/fold ... bo1HPqRz6f

I notice that C58A is missing from the Makvision. I wonder if that's the S-correction cap for 15kHz mode? Mine is 0.56uF just like the Betson. I'm wondering if I can increase it to 1.0uF like the Rodotron. I've read that those caps are only switched in when in 15kHz mode, so I hope I wouldn't have to include a toggle switch. That wouldn't be a solution since I'm running a MAME cab and it switches resolutions in GoovyMAME on the fly.

On this schematic (I know it says 30-50kHz, but it has C58A, so maybe that's a typo? -- a value of 0.27J seems wrong):
https://na.suzohapp.com/pdf/service_pdf ... 0D2rev.pdf

I wonder if LK-228-050-10 is the HL coil. Maybe it's gone bad?

I recapped all the electrolytics about 7 years ago with Nichicons and this problem has come back. The Nichicons I thought improved the problem, but it's back to being as bad as ever. Any help would be greatly appreciated. This chassis has never been perfect since I got it over 16 years ago. I'm almost thinking of replacing all the film caps with polypropylene, but I'm not sure that would fix my issue. I'm not super familiar with monitors, but I've done lots of board rework.

As a side note, if you power on this chassis holding MENU UP, you get the advanced menu. The HL adjustment there doesn't really do much. Interesting too is that the menu doesn't hold over to 15kHz mode. In that mode I just get the regular menu. The advanced menu works for all other resolutions and frequencies though...