ZN-1 Board stuck at color palette screen

[iTRDC2]

Hello,

I have a faulty Capcom ZN-1 PCB (Battle Arena Toshiden 2).

When I turn on the arcade, the board goes to color palette screen and stays there (it is stucked. At least seems becasuse when I press the test button it does not go to test sreen).

I tested all ROMs using my Miniprog to read them and then I compared with the game Mame ROMs and they are all OK.
The board does not have any visible bad traces.

I searched in google and also here on the forum and did not found any relevant info regarding what could be the root cause or at least how I could continue the troubleshooting.

Anyone have a clue what could be the problem?

Thanks in advance and happy gaming.

BR,
iTRDC2

 

[Hammy]

What color does it stick on?

 

[iTRDC2]

What color does it stick on?

It displays all colors and then it freezes.

Best Regards,
iTRDC2

 

[iTRDC2]

A photo of the colors palette

What color does it stick on?

Here is a photo.

Best Regards,
iTRDC2

 

[Hammy]

This is saying motherboard good, romboard needs checking
Bios OK, CAT chips (top and bottom ok) , Decrypt OK , Execution problem.

If it turns out to be the motherboard it will be something unusual like work ram.

 

[iTRDC2]

This is saying motherboard good, romboard needs checking
Bios OK, CAT chips (top and bottom ok) , Decrypt OK , Execution problem.

If it turns out to be the motherboard it will be something unusual like work ram.

Hi Hammy,

Thanks a lot for wisdom comments .

In the meawhile taking into account what you said I putted my attention on the ROM Board.
Since I had already tested the ROMs (both Mask ROMs and EPROMs) I decided to take the next step and test the PALs. I re-seated two of them, the socketed ones (Bank 0 and CS0CNT) and kabum, the game is now working .

Nevertheless if you take a look at the color palette the colors are not OK.

I noticed that if I aplly some pressure with my finger somewhere near the 74LS253's ICs (on the lower board) the colors turn good, but if I remove it again it gets bad again.
All components seem well soldered.

Any idea how to solve this ISSUE?

Thanks once again.

BR,
iTRDC2.

 

[Hammy]

2 ways to debug this:

1: Microscope and looking for the loose connection
2: Check the video levels , you can start at IC 201 and trace towards the edge connector or work backwards from the blue pin and see where the signal drops.