30 May 2018

Terra Force - Nichibutsu 1987 (Repair log)

Game worked except background plane was mostly missing:

My eyes quickly spotted "shiny" RAMs on the top board so I started to probe them:

And I quickly found video RAM @ F17 was faulty. I installed a new one and problem vanished:

Game fixed.

23 May 2018

Sega 834-6510 I/O board reproduction - part 1

As far as I know this board is used only on System 24 for driving games (Hot Rod and Rough Racer) and golf games (Jumbo Ozaki Masters and Dynamic Country Club).
It handles analog inputs (e.g. steering wheels, gas and brake pedals, etc.).

I've been looking for one for a very long time and finally took the decision to reproduce it. Still it wasn't easy to find an original board as model for my reproduction.
Once again a German collector came to my rescue and lent me his board:

And here's my CAD reproduction:

It's quite expensive to build due to ICs used being dropped for a long time (D4701, M5203).

16 May 2018

Xexex - Konami 1991 (repair log)

PCB was in very good condition but threw a "SOUND MEMORY BAD" error on boot up:

Of course this error isn't in the manual and even after an extensive online search I haven't found any mention of it anywhere...
Well after some probing and testing I came to the conclusion it had nothing to do with the RAM chips on the mainboard. I mistakenly thought it was caused by a bad '054539' custom chip (samples player) so bought a replacement pulled from an other game from Caius @ jammarcade.

I pulled the suspected faulty chip and cleaned the pads:

Then I aligned the replacement chip and soldered the 4 corners:

Then applied some SMD soldering paste:

And used hot air for soldering:

Only to discover it didn't change anything regarding behaviour of the board, still stuck on the same error.
So I had a look in the code and found this error is reported when the RAM present on the custom sound module is bad. Many of you know there isn't any RAM on this module but instead there's a '054321' custom chip handling, amongst other things, sound volume. I came to the conclusion the chip embed some RAM, which makes sense.
I swapped the sound module with a working one and indeed fault followed the suspected faulty one. I went even a step further and swapped the '054321' custom chips between modules: and boom we've got a culprit, the '054321' was obviously faulty.

Game fixed in a sense (although I don't have any spare '054321', at least fault is identified, it's just a matter of soldering a good chip now).

I then had an other discussion with Caius who told me he encountered similar symptoms on a Bucky'O Hare board few days later:

Damn it... I should have waited few more days before starting this repair.

9 May 2018

Super Pang - Capcom_Mitchell 1990 (repair log)

An other suicided game with additional problem: instead of the ligth blue screen the suicided game should display I was greeted by a black screen...

I followed the desuicide procedure found on the "Dead Battery Society" website (http://www.arcadecollecting.com/dead/), and then fired the board: black screen just as before but audio and controls were working. Game was playing blind, I could add credits and start a new game.
When you have no video at all it's always good to start from the JAMMA connector and then follow the signals. In this case red, green and blue signals on the edge connector were stuck low. I then probed the colours RAMs (two of them) @ 8C & 9C: all data pins were stuck low. I took the chance of piggybacking them and obtained an image. Colours were not perfect but this is something to expect when you piggyback chips as the faulty chips underneath can drag the signals low or high and the connections aren't at their best.

I pulled the faulty RAMs and both turned out to be fried on my programmer. I installed sockets and put fresh RAMs in them and was greeted by a fully working game:

Game fixed.

2 May 2018

Cal.50 - SETA 1989 (repair log)

An other greasy board covered by CRC. I first cleaned it after removing all the socketed chips and the battery (used for high scores saving).

Once the board was completely dry I tested it: game was dead, sync signal wasn't valid.
Probing the main CPU (68k) I found reset signal was held low. There's a reset button on this board so I had a look at it: I tested continuity and it turned out it was stuck depressed. I replaced it but saw no improvement. Next to it was a voltage control chip named "RE5VA45AC". It was dead too, possibly because the button has been kept depressed for a long time when it's supposed to be just an impulsion. I couldn't find a replacement part for it so I simply removed it and bridged pins 1 & 2 which was enough to repair the game:

Game fixed.