CPS1 main boards and their repair

Solder

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Is it just me or are CPS1 main boards a complete pain to try and repair? You can't get at the components to check them out as the ROM board obscures the main board. Probing the solder side is the only option, but on the smaller boards with mostly surface mounted chips this is rendered nigh on impossible.

The smaller main boards are the worst - at least the larger type gives you some access to the sound and color circuitry, but with the smaller boards you can't even access that.

That's my moan for the day. :)
 
I guess if you are really interested in testing these boards you can build jumpers to allow you to seperate the boards. I have been considering doing this, but every repair I have had to do on these boards has been pretty simple so far and I haven't yet needed to build the jumpers.
 
I guess if you are really interested in testing these boards you can build jumpers to allow you to seperate the boards. I have been considering doing this, but every repair I have had to do on these boards has been pretty simple so far and I haven't yet needed to build the jumpers.

what like just re-capping the audio sections and such? what actually goes bad on these when the video starts getting all jacked up, RAMs or something?
 
So far I haven't had to recap anything. Most of the time I just reflow solder for the socketed chips.

What do you mean by the video getting all jacked up?
 
what like just re-capping the audio sections and such? what actually goes bad on these when the video starts getting all jacked up, RAMs or something?

The most common fault is the sound failing, simply down to a bad Z80 - easy fix. Problems arise when you have faults with the colors and graphics. The main graphics custom seems to be a common point of failure, as do the graphics RAMs and the TTLs around them. Very hard to diagnose when you can't easy probe the chips.
 
The most common fault is the sound failing, simply down to a bad Z80 - easy fix. Problems arise when you have faults with the colors and graphics. The main graphics custom seems to be a common point of failure, as do the graphics RAMs and the TTLs around them. Very hard to diagnose when you can't easy probe the chips.

^ kinda what I was alluding to, lol

the Japanese sure don't make it easy. it's probably been about 15 years since I last saw a CPS1 board, and even then it just looked like a green board.
 
It's VERY difficult to test them. The locations in memory seem to shift depending on the game. Plug in one B/C board set and get foreground graphics issues... put a different one in and the background goes crazy.

I got tired of trying to figure them out.
 
most of cps1 i found were easy enough to repair. i remember one that need a recap, that's cap for audio amp :D

i found one that had graphic glitch, and i suspect one/more of the RAMs (vertical package) bad. guess how i found them, just keep the board run, then slowly touch the board from bottom, beneath those RAMs. and i felt that one position was hotter. i replace that RAM, and whoa.. it worked :D
 
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