MTG-2901CN Monitor V Sync Hold Issue

[Goodwinsplace]

Went to visit a friend today that has a few cabs that need a bit of TLC.
The Q Bert has been fitted with a few different bits, still running an original PCB but with a modern switching power supply and I think the monitor is a Happ Vision? The only number I could find on the chassis was MTG-2901CN.

The monitor was running up until a recent power up and then it was scrolling pretty fast side to side (v sync in TATE mode).

I've tried the adjustments on both the adjustment board (brightness, contrast, v size, v pos, h size, h pos) board and got some level of success by adjusting the V-Hold on the main chassis, but the pot is so sensitive it isn't possible to stop it in the right place and it always has a bit of creep even if I manage to stop it out of location.

Is there anything else I can check for a v-sync issue? Could it be the pot on the board? Recap needed?

Video of sync creep, this is probably the best I've managed to get it without it scrolling crazy.

https://photos.app.goo.gl/KgbkZKLcjgvRku2t5

V-hold in red circle:

Goodwinsplace2022-08-03 20:01:48

 

[Goodwinsplace]

Welcome any input on this. Worth a recap and reflow to start? Do the pots on the board go often?

 

[gunblade]

is the vertical sync wire connected to the sync line from the game board?

 

[Goodwinsplace]

is the vertical sync wire connected to the sync line from the game board?

I can take a look but imagine it is. The cab hasn't moved in several years and was working up until recently so think it's more of a failure than poor install.
Although whoever converted it to a modern power supply and this monitor did a bit of a hack job.

 

[gunblade]

not changed the game board?

 

[Goodwinsplace]

not changed the game board?

Nope. Stock PCB, I came down to look at lack of input from the controls. The cab had been offline for ages due to them thinking they had a faulty 1 up button, but all controls were out - sorted that now.

The monitor was fine when it last booted and I'd seen it running maybe two months ago. The owner isn't the type of guy to play around and we even had to find the key for the back panel.

 

[gunblade]

maybe bad solder joint, maybe leaky cap, maybe just bad connection due to corrosion

 

[Goodwinsplace]

maybe bad solder joint, maybe leaky cap, maybe just bad connection due to corrosion

Thanks I'll pull the chassis next time I visit and give it a going over. Can't see any cap kits in UK for this model so will look to build my own up if needed.