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Namco Rompers repair log

Aug 032024

I’ve had this board in my collection for some years and I’ve made some repair work on before (replacing the cus120 on the CPU board, might put up a repair log on that as well).
I was going through my PCB collection and found that the game would not boot, there was only a black screen and not even the usual klonk sound as Namco System 1 games usually do.

Started with the basics, probed the Program ROMs with my logic probe and I did see some activity on the address and data buses.

Decided to dump the Program ROMs and verify them and they turned out to be ok.

So I started to probe the address and data buses again and found an address line (A2) that was stuck low.

Traced this line back to a 74LS244 at E10

74LS244 is a buffer and according to the Pac-Mania schematics, pin 14 is the output which has its input at pin 6 and there was activity there

This made me quite certain that the 74LS244 at E10 was bad.
But just to be certain, I removed all Program ROMs and the Custom key chip, so none of them would interfer.

And the fault was still there.
I quickly desoldered the 74LS244 and tested it with my tester as bad

I soldered a socket in its place and replaced the IC with a known good one and now the game booted up again

Double Dragon repair log #4

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Mar 122011

The sound circuits on these DD boards really were bad!
Another one with dodgy sound, music was intermittent and half the SFX were really really low.
Did a full capacitor replace on this board for the sound, half the caps had started to leak. This brought back the music.
The sound effects were a little confusing. Like the last board I could see the data going into the M5205 chips but on IC80 there was nothing coming out of pin 10. I replaced the chip but this time there was no change. The board has had the op amps replaced at some point and there was a little rework done on them. Pin 5 (input) of the op amp at IC97 was shorted to pins 6 and 7 (output) effectively bypassing the op amp altogether, this explained why the sound was really low. Removing the short fixed the sound.
Another one destined for eBay.

Rainbow Islands repair log #1

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Mar 052011

Got hold of a very poorly Rainbow Islands Extra board.
This board had some repair work done previously. There are a few burned out tracks and some dodgy looking wire links.

On power up it just showed a black screen, time to break out the Fluke 9010a.
The Fluke showed I had active interrupt lines. The 68000 CPU has 3 interrupts, IPL0, IPL1 and IPL2. IPL1 and 2 are tied to +5v (they are active low therefore unused here). IPL2 was stuck low.
I traced the line to a nearby 74ALS74 chip and then back to a 74LS273 (IC32). Regardless what the inputs were doing, the outputs were all stuck low. I replaced this and tested, still a blank screen. I check the 74ALS74 again and although all the inputs were now present and correct, its output to IPL2 was still stuck low. I piggybacked a new IC onto it and the game came to life. Replaced the IC.

Now the game booted up I could see that the colours of the character sprites were wrong, mainly black.

This caused me a lot of headache as the colours came good when I put the logic probe on different pins of different IC’s. I determined which IC was partially responsible for sprite colours by interrupting lines on various logic chips. I found that if I toggled pin 9 of IC35 (74LS157) the colours came good more regular. I removed this chip and tested it in my logic tester, it passed but if I put it on a loop it would intermittently fail. Replaced this and the colours were now back to normal.

There is also a problem when the sprites are facing left where it shows a broken character but still facing right. The pictures below shows the broken up boss sprite and broken rainbows when fired to the left.

This ended up being a short on pin 15 @ IC38 (74LS153). This pin was shorted very slightly to an exposed track running next to it. Removing this short fixed the graphics completely and the game is now 100%.
Very pleased.

Street Fighter Zero 2 repair log #1

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Mar 022011

Got this for repair today. Was under the impression it had suicided but this had jailbars on all screens starting from the Q sound screen.

On opening the case it was obvious what the cause may be.
One of the gfx maskroms was only half fitted.

Refitting the Rom fixed the problem.

X-Men Children of the Atom Phoenix error

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Mar 022011

I got 2 CPS2 boards today for repair.
One of them was a Children of the Atom game that had suicided, simple enough.
I erased ROMs 3 and 4 and burned the bootleg code. The game booted up to the copyright screen then bombed me out with an error.

After a bit of playing about it turns out that the installed ROMs were from the Japanese version of this game and this is different from the Euro version (which is what the Phoenix ROMs are based on) so I had to erase ROMs 5 – 10 and reprogram them with the Euro version.

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