Battle Garegga 1996 HK PCB Version / Color bleeding

[Vendest]

Hi, First time posting here but it is obviously the right place to seek help & advice.

Tested this board in an arcade cabinet and with a supergun. There is a color bleeding from the text and sprites on the foreground as per pictures.
I also noticed that one of the original capacitor has been replaced with a ceramic one 0.1uf (103)

https://imgur.com/a/Dib1cL7

Could someone point me to the right direction or even provide schematic diagram?

Thanks,
Vendest

[mikejmoffitt]

Turn down your monitor's gain.

Is your second shot with screen flip enabled?

[Vendest]

Yes that's something I forgot to mention, I did set the DIP to flip and took a shot as well.
Strangely color bleeds constantly towards the same end of the screen regardless of the display being flipped or not.
I have started mapping the Video DAC pinout. Was thinking to disconnect one of the video color signal at a time to isolate the problem. (provided that the problem is linked to video signal)

I am using a supergun and consumer grade CRT so there no much adjustment I can do aside from geometry.

[mikejmoffitt]

It isn't a board defect, no need to overcomplicate it. The bleeding is your tube and/or driving transistors being saturated. The contrast / gain is too high on your monitor, at least on your red gun. If your monitor / TV has a "Contrast" setting, this is the one you want to reduce.

Garegga's outputs are a little higher voltage than some of my other boards, so I have to turn down gain when I swap it in to avoid similar bleeding problems.

If you can't adjust gain on your setup, then you can build a resistor divider to attenuate the signal.

[Vendest]

You are right, I've checked at the jamma connector that red video signal outputs higher voltage than blue and green signal.
I adjusted the potentiometer from the supergun until red color completely disappeared so the bleeding.
I think the potentiometer should already act as voltage divider
Tried adjusted the color settings and mainly contrast on the TV but no improvement.

https://imgur.com/a/xawD7Y2

[mikejmoffitt]

Measuring the red output at the JAMMA edge isn't really appropriate, since it changes rapidly and isn't necessarily balanced between scenes. However, if this is your only game with this problem, it is possible that your DAC could actually be damaged, but I highly doubt it.

[Vendest]

So I have isolated the fault by removing all 5 resistors on the DAC for red video signal.
By re-sitting them one after another I could identify that R3 is linked to red color bleeding.
That line comes all the way from the FPGA chip labelled with a sticker A04370 (U30) - Here under the DAC pinout
I've tried adding a voltage divider on that specific line which outcomes with reduced color bleeding but affects directly other sprite colors so a no go fix

https://imgur.com/OhpWM8b

Yes I noticed that the voltage fluctuates on the Jamma connector however there is a great gap against voltage from other 2 colors.

Thanks for the help!

[mikejmoffitt]

A common fault on Garegga boards is apparently one of the buffers used for the DAC right near the JAMMA edge. They are 74HC273 chips at locations U12 and U13. Figure out which one drives R3, and check that one. Probably the GP9001 is okay, so I'd put my money on the buffer first. I have a friend's board with a similar DAC issue causing some color balance issues, and my board had to have these replaced. This thread discusses Garegga DAC issues and the fix information comes from DaveK, who has fixed a bunch. I'm willing to bet one of those chips is your issue.

[Vendest]

Sorry for the late reply but it took some time for me to receive the new chips.
It worked after replacing U12 & U13!
Thanks for the help!

https://imgur.com/dVDtzEY

[mikejmoffitt]

Great! Glad it was nothing else.