31 Oct 2018

Hyper Olympic (Track & Field) - Konami 1983 (repair log)

When I first powered this board is was mostly working: title screen was corrupted but sprites were OK and I could see runners during the intro.
However after few seconds it started to fail hard: background disappeared, then texts and finally sprites...

As always a quick inspection of the board revealed many Fujitsu TTL chips:

And as usual I probed them all and found 8 bad chips (far less than expected given my previous repairs of Fujitsu plagued games):
- 2 * LS74
- 1 * LS138
- 1 * LS157
- 2 * LS244
- 2 * LS245

After replacement I powered the board again fearing for more damage, but:

Board was perfectly working with sound and controls!

Game fixed.

17 Oct 2018

Sega 837-6443 - System 24 FD controller reproduction

Floppy based games on System 24 are becoming incredibly hard to find, not that rom based games are easy... but at least way cheaper, probably cause they are crappy Mah-jong or Quiz games in Japanese.

I designed a reproduction of the floppy drive controller so anyone with a rom based game can enjoy floppy based games:

It's a 1:1 replacement, same dimensions, same layout and fits in place of the OG one. And it works just great :

10 Oct 2018

Act Fancer - Data East 1989 (repair log)

This board was given to me as faulty in a deal.

Upon power up game was stuck on a garbage screen:

I quickly noticed work RAMs were shiny ones (known to have a high failure rate) but I dumped the 3 program ROMs first: they matched the Japanese rev.1 romset in MAME. Probing the RAMs didn't revealed anything weird but by using the oscilloscope I could "see" main CPU was sending data cyclically. Cleary no valid code was executed and CPU was stuck in a loop. I pulled both work RAMs and both tested bad on my programmer. After replacement game booted mostly fine, with sound, texts and background but sprites were replaced by big misplaced blocks of garbage:

Again I pulled and dumped the 8 sprites ROMs but they all matched. RAMs didn't show anything weird either so I started probing the TTL around and noticed one of the inputs of the LS10 @J4 was stuck low. Being a triple NAND gate it meant the associated output was also stuck (high this time = NAND). I tracked the signal to the Q output of one of the latches of the LS74 @J1. All inputs were correct with activity where it should be but outputs Q and /Q were just stuck. Piggybacking a new LS74 chip on top of the suspected faulty one cleared the issue. I replaced it and sprites were fully back:

Game fixed.

3 Oct 2018

Sega 834-6510 I/O board reproduction - part 2

This time I received the blank PCBs.
As you can see layout is identical to the OG one:

Side by side comparison once assembled: