5 Jul 2017

Tatakai no Banka/Trojan - Capcom 1986 (repair log)

This game is part of a lot of games from Hell I repaired few months ago. Those games had so many faults I wonder what caused them... I would go for bad powering (over voltage).

So this the Japanese version of Trojan known under the name of Tatakai no Banka. It's made of two boards with hidden traces under a copper layer on both sides covering the whole board. Schematics are of course not available. It took me hours to figure out which signal was connected where...

1) First inspection, first hope, first fail...

As usual I spent some time to inspect the board for damaged chips, etc. I found someone previously worked on the top board and that the work RAM (6264 type wide) and the LS04 next to it (used as a crystal driver) have been put on sockets and replaced. I tested both and found out the RAM was fried (weird as I could see it wasn't a pulled part but a new one). I replaced it. I also noted that one of the flat cables between the two boards had wires severed. I fixed it too.
Ok that could definitely explain why the board has been given to me as faulty, I already found and solved two issues. I dug out my Capcom classic adapter and powered the board, full of confidence, only to be greatly disappointed by a black screen with no sound...

2) Fujitsu plague, as often

Ok that was disappointing but not enough to discourage me. The inspection of the board made earlier showed me there was some Fujitsu chips peppered on both boards. I probed them all and found bad:
- 4 * LS86 @ 3J/4J/5J/9K on top board
- 1 * LS32 @ 1E on bottom board
New hope, new fail... Black screen no sound.

3) Texas Instrument and Mitsubishi are partying too

Well, this time I dumped all the ROMs (25 of them!) but they were identical to the MAME romset.
Back to the basics. I probe the vital signals on the main CPU (Z80) and main RAM and found /CE signal was stuck high on the latter. This is where the hide and seek game begins. Traces being hidden I tested continuity of every single leg of every single chip on the top board and discovered the signal was coming from a LS139 @ 12F (Texas Instrument this time). I replaced it and tested the game: black screen with no sound...
I continued my investigation and found ROM TB01 had also its /CE signal stuck high. An other LS139 @ 7C was fried. At this point I thought it would be wise to test the 2 remaining LS139 of the board: the one @ 10D was dead. I replaced the 3 (out of 4) faulty ones and...Black screen with no sound...
I then moved on the data bus signals: some were weird. Found a faulty LS273 @ 10B. I replaced it and this time game booted with corrupted graphics and music was absent.
Ok this wasn't a victory yet but after all things had improved.

4) Fixing graphic glitches... And an other annoying fault

I jumped on my camera but before I could take a picture game died... Well not really. In fact it worked for 10 seconds and then stopped to a black screen with no sound. If you let it cool down it would work for an other 10 seconds. I first continued my investigation on the graphic problems: buildings were cut in half horizontally. An other Fujitsu chip had died during the repair, replacing the LS157 @ 12D on the bottom board cleared the problem.
Now I was left with a screen covered of spots:


The LS273 @ 9H on the top board was faulty. Graphics were finally correct:



Before a minute later text layer went crazy:


The LS273 @ 9F on the top board had decided to die during the repair too. I replaced it which restored the texts:



Now the annoying hanging issue: if I turned down the PSU to 4.5V game would play forever. Not an easy fault to troubleshoot. I didn't find any abnormally hot chip. So I started to piggyback every chip not related to graphics or sound. I found a faulty LS161 @ 1L on top board.

5) Fixing the sound and some new appearing faults

I started to probe the sound section and... Game died again: black screen no sound... Found a dead LS74 (Mitsubishi) @ 6J on top board.
Ok back to probing and... Guess what? Game died! Found a dead L157 (Mitsubishi) @ 5M on top board.
Self control, deep breathe. Back to the repair.
So music was absent and probing one of the two YM2203 revealed it had no ouputs. I replaced it but heard no improvement. However with the help of an audio probe I could now hear the music (distorted) on its outputs. So the fault was in the later stages of audio processing. I probed the two DACs (YM3014) and both had no signal on their output. I replaced both and music was fully back.
Game fixed! Game Fixed!

NOT!

Now the title screen was corrupted:


ROM TB23 on the bottom board kicked in the bucket.




I burnt a new one in a plastic EEPROM to keep the clean and tidy look of the board.

Game fixed.

Family portrait:


- 1 * YM2203
- 1 * 6264 RAM
- 1 * 24256 mask ROM
- 3 * LS273
- 3 * LS139
- 2 * LS157
- 1 * LS161
- 4 * LS86
- 1 * LS74
- 1 * LS32
- 2 * YM3014

2 comments:

  1. Wow, awesome job as always Apo, perseverance is the key :)

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    Replies
    1. Thanks ;)
      Sometimes it can be a bit disappointing when you discover a custom chip is faulty after having spent hours on the board and fixed many other issues. It's always a gamble!

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