Burnin' Rubber (Bump 'N Jump) repair

This was bought in a job lot and listed as untested, I thought there was a good chance it would work after making a jamma adapter for it but no such luck.

Powered it on and got nothing but a black screen, I could coin up and there was music so it was mostly working. Checking with a logic probe I had sync but no red, green or blue, all three pins were floating.

I decided to check the bottom pcb with the trusty hp logic comparator, this was a little tricky as the top board covers most of the bottom one. I was able to flip the top pcb to the right being careful not to short anything to the jamma adapter. I eventually found a bad 74LS74 at B11.

Bad 74LS74 removed.

New one fitted.

 Repair complete.

ABI Boardmaster 4000 repair

Another new toy to play with, this is a very useful bit of test equipment that can test chips not only out of circuit but also when they are still in circuit. I bought this knowing it had some issues but they are very rare and sought after so you cannot be too picky.

First I wanted to fix the lcd backlight which would flash on for a second then go off, this is a common problem with these things. It also made it hard to read the self test fail messages so looking on UKVAC forum there is a thread explaining how to wire a generic laptop inverter in place of the old one. I was impatient though and did not want to wait 2 weeks or more for one to arrive from China. The two surface mount capacitors looked like they had leaked which I've seen many times repairing Sega Game Gears.

I replaced them with high quality radials and the screen was now nice and clear and made it easy to read the 14! fail messages. I won't go over all the error messages again here but if you want to read more check this thread on UKVAC.

Twelve of the error messages gave part numbers to six different relays which from reading in circuit with a multi meter I could see were bad. The other two error messages didn't point to any parts but I was able to find them by metering every relay, it turned out to be two on the out of circuit testing pcb.

After replacing the eight bad relays...

the repair is complete.

Suitable replacement relays can be found here. - Thanks trm.

Taito AA017751 cocktail power supply repair

I am very slowly restoring a Taito black & white Space Invaders in between other projects. The time has come to rebuild the power supply, I fully recapped it including all the tantalums. One of the resistors was burnt out but there's no documentation online for this exact power supply, so I had to hope that the reading of 33 ohms was correct and replaced it with another 33 ohms.

I then tested it in the cabinet and the 12v, 18v and -5v were all spot on but the 5v was putting out 8.5v! luckily I didn't have the board hooked up at the time or it would have gone up in smoke.

Adjusting the 5v pot made no difference to the voltage. I went looking for documentation online again, backflipper on ukvac pointed me to a schematic in the moon alien manual but after looking it over my power supply is very different.

Then I found a very old newsgroup post by John from John's Jukes (www.flippers.com) that mentioned he had schematics for the AA017741 power supply. I sent an email and got a reply and a copy of the schematics almost instantly, thanks again John. The layout is slightly different but otherwise looks the same as the 51 version.

I looked over both the schematics and the board again and I narrowed the problem down to the TA7089P voltage regulator. A chip that hasn't been made for years and can be hard / expensive to find.

For a new old stock one anyway, I went the utsource route which basically means used pulls that have had their legs sanded and dipped in solder to make them look new again. I don't like this as it makes the legs extremely fragile but they are cheap and everything I've had from them has always worked.

The TA7089's arrived after about two weeks, I fitted a 'new' one to the power supply fired it up, 5.05v on the 5v line, success!.

I replaced the 555 timer too as chances are the 8.5v killed it.

Next the monitor speaking of which, TC if you're reading this I might have a spare chassis available at the end of this project.

My cap map is famous.

 

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CPS1 B Board repair

This capcom CPS1 B board (middle board) was running but the video output would not sync, usually this would be a C or A board fault but I'd already ruled them out by swapping them.

I went around the board checking the connection between the A and B board was solid with a multi meter and found two pins not making contact near the C board. This part of the board had taken a nasty knock at some point and cracked the near by resistor array in half, but one problem at a time.

First I desoldered the connector that had the two missing connections.

Now I could clearly see the two broken pins.

Once I replaced the connector with one from a scrap board sync was restored but there was a graphics glitch, most sprites had vertical lines going through them.

I replaced the two resistor arrays next to the c board as one was broken in half and one had a leg broken off. This made no difference.

I was convinced the issue was in this area since I'd already found so many other issues there. Running the board without the C board means the game won't work but it's the only way to access that area and probe around while the board is running.

I checked every pin on the two resistor arrays and noticed one was high while the others were all toggling. A closer look I could see the through hole had come away from the trace and probing the trace it was toggling away.

A tiny piece of kynar wire to repair the trace and the repair was complete.