I got this board a few years ago when I got a Pac-Man cabaret cab that had been converted to Trojan.
The whole cab was sold to me as not working so I assumed the board wasn’t booting either I converted the cab back to pacman and put this board aside until this year
So I fired up the board and it booted up just fine. However there was absolutely no sound coming out.
One of the issues with this board is that there aren’t any schematics available for it.
Luckily the sound section is almost identical to Ghost n Goblins.
Since the traces are visible on the board, I drew them for help on the back of the board.
Crude but it helped figure out things a bit.
It’s got that same sound module (85H001) to drive two YM2203 (3 channel sound chip)
The signal is then fed to a YM3014 DAC, and LM324 Op-Amp and a final HA13001 power amplifier.
Probing the YM2203, YM3014 , LM324 I can see signal coming out of all these and into the input of the power amplifier .
However there’s nothing coming out of the HA13001 so I’m assuming this is the culprit here.
Removing it, half the legs broke off . No wonder it wasn’t working
I fitted a new one and the sound came back right away and I was able to enjoy a quick game of Trojan
A quick and easy one but you need these every now and then
And as usual, for those who prefer the video format:
A while back I got my hands on a cheap CPS1 set for Street Fighter 2 CE. The reason it was cheap was that the A board was not working. As we know by now, these A boards are dying quite fast and in some cases the culprit is the Custom CPS-A-01 chip for which there are no know replacements as of yet.
Let’s have a look at what we get on screen first
So it seems we’re only getting half the lines in the sprites and , while it’s not visible on a screenshot, the other half is flickering slowly too.
Looking at the schematics we can see the two parallel banks of rams processing each odd/even lines of sprites. These are coming straight out of the CPS-A-01 GPU IC. Let’s check out the DT/OE enable lines or the rams first.
Looking at them in with the scope reveals a couple of issues:
The bottom one is pin 21, and it’s not really toggling apart from that one regular jump, while we can see that the other line is toggling all the time. This is why we’re only seeing half of the sprites: one bank is not being enabled.
The other issue is this jump on both lines which is most likely why the entire sprites flicker regularly.
These are coming from Pin 21 and 47 of the cpsA .
bank A pin 21
bank B pin 47
Tying the enable line of bank B to bank A will restore the sprites but we still have the issue of the flickering sprites… in a nutshell, the CPS-A chip is fried and this A board is toast.
Luckily a viewer of the youtube channel (thanks Kris Ankers!) sent me a spare A & B board.
The board is in unknown working state . Checking the few remaining proms it’s another SF2 CE , not that it makes much difference here as we’re only interested in the A board. Let’s replace the A board on my other stack and fire this up
…nothing. board is dead.
A quick visual inspection reveals a few corroded badly corroded sockets on the BUF1 and ROM1 pals. corroded is an understatement here too since the socket were missing legs that had completely disintegrated.
Let’s put new sockets in place and see what we get.
Still no boot. I took both pals from my other set and dropped them in.
After some more swapping I found that the Rom1 pal is working so it was just the BUF1 pal that needed to be replaced.
Success!! The board is now booting and playable. Sound is also working fine.
But it seems we’re missing the red color.
A look at the schematics tells me me which ICs are handling the rgb output. We’ve got two rams outputting to 2 LS273 flip flops. This is then sent through ls07 and ls367 buffers, through resistor arrays before being output to rgb.
The difficulty here is that apart from the legs of the rams and resistor arrays which can be probed from the underside, the other ICs are SMD and hidden by the b board so I am not able to probe the legs. Time for some logical guess work :
Since the pairs of ls07 and ls367 are shared across the colors it’s unlikely one of those has failed or it would affect more than one color (still possible but unlikely)
Two resistor arrays are needed per color. If one had failed, we’d get some red at least but here it’s all gone and while it’s possible, it’s unlikely two are gone
So I’m first going to look at the RAM at 1C and the 273 at 4C
Probing the RAM seemed ok so I decided to remove 4C and replace it.
Behold a working (for now) Street Fighter 2 CE CPS1 stack. It’s a bittersweet victory though as there’s no telling when that CPSA chip will fail (not if but when) . But for now I’m going to enjoy some Capcom fighting. Thanks Kris for the PCB donation !