21 Mar 2018

Street Fighter - Capcom 1987 (repair log)

The first Street Fighter from Capcom, not so common.
First version had 2 "air" buttons (punch & kick) acting as analog inputs (the more pressure, the stronger the punch/kick) with hoses connected directly to the top PCB (game is a massive 3 board stack). Then they changed the design to the now very common and popular 6 button layout (low/medium/high punch/kick) as some players used to abuse the cabinet (even jumping on the buttons!). This is the version I own (Japanese with protection).
Boards were in good condition, however I quickly noticed they were full of Fujitsu chips. A painful job in perspective (or soul crushing as my friend Kelvin like to say).

I powered the board and it did nothing more than a black screen.
I started the repair with the bottom board as it contains the main CPU.

1) Fixing the bottom board: main CPU/background

Probing the buses revealed the CPU (68k) quickly switched in high impedance. Program ROMs and work RAMs (2 * 62256) were fine, board was clean with no visible severed traces so I went to probe the logic between them (mostly LS2455). I couldn't test them properly, being tri-state and bi-directional IC. I chose to remove all the TTL chips from Fujitsu in the CPU area: 2 LS245 turned out to be bad.
After replacing them the game booted but with many issues (again I forgot to take a picture):
- highly corrupted background
- no sprites
- wrong colours
- sound was present but with a cyclic click noise
I probed the rest of the bottom board and found many other dead Fujitsu chips:
- 5 * LS86
- 1 * LS138
- 1 * LS174
- 2 * LS273
- 1 * LS367
I fitted new parts and this fixed the background:

2) Fixing the top board: colours and sound

I then moved to the top board rather than the middle board as I wanted to be sure the wrong colours weren't hidding something else.

Yes you guessed right, more dead Fujitsu TTL:
- 1 * LS174
- 1 * LS245
But that was not all, one of the colour RAMs was dead too (CXK5814 = 6116 type).
Colours were now OK, so as title screen.

3) Fixing the middle board: sprites

With the background and colours now correct I could see the sprites were not totally absent:

Again dead Fujitsu TTL:
- 3 * LS86

But replacing them had no visible impact on sprites.
So I moved on the next probable culprits: shiny RAMs. They were 6 of them on that board and 2 were dead (TMM2015 = 6116 type).
This time sprites were fully restored:

Game fixed.

- 8 * LS86
- 1 * LS138
- 1 * LS157
- 2 * LS174
- 3 * LS245
- 2 * LS273
- 1 * LS367
- 2 * TMM2015
- 1 * CXK5814

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