27 Mar 2019

Raiden II - Seibu 1993 (repair log)

Game was dead, no main or sub CPU activity, however sound section was alive since adding a coin would make the associated jingle play.
Board was covered in cat/mouse pee (nasty smell) so was cleaned with a lot of other dirty boards.
Then I started inspection and found the custom chip used for security (SEI1000) had a good 40 pins lifted. I reflowed it and game booted with perfect graphics and fully working controls (for both players):

However music was composed of drums only but samples were working fine.
With my audio probe I started with the YM2012 since you have both the digital signal (pin 4) and the analog signal (pin 12) available on that chip.
Music was present on the digital side however there was nothing coming out on the analog side. Using a logic probe I found signal was stuck high.
I replaced the YM3012 and music went back to normal.

Game fixed.

20 Mar 2019

Raiden - Seibu 1990 (repair log)

Got this board in a lot of faulty boards in a trade. It came in an antistatic bag with a note written on it "will not boot".
Upon first inspection I noticed board was very filthy so probably hadn't been stored in the bag all the time. Also custom chip UEC-52 was completely missing (ripped from the board). Fortunately Caius from jammarcade.net sells reproductions of it, only I placed an order for one few days ago for an other board which had the chip scratched to the point only legs of the SMD ICs mounted on it where left. At least I'll have the ICs reference from the reproduction.

I usually find very few information about what a board should do with missing elements, which is a pity since this can be extremely useful for repairs.
Here are few things I can tell:
- without the UEC-52 custom chip (DAC used for colours in SIL22 package) the game still boots and plays blind
- the board requires -5V for sound, this probably explains with the board was noted "will no boot" when it fact it did but played blind, only to notice it you need -5V
- sound part is completely independent so even with a completely dead main CPU or sub CPU you are still able to hear the coin jingle if the sound part is alive since it's an interrupt (jingle is played whenever you insert a coin, wherever you are in the game)
- without the OBJ1 daughterboard game still boots and plays blind (black screen)

So as said game wasn't completely dead but played blind due to the missing custom chip. Fortunately I had received an other Raiden board few weeks ago which was perfectly working (and turned out to be an undumped set).
Could it be as simple as installing back the custom chip to get a fully working game?

Not really, I did so and then found valid signals on the RGB outputs, which was progress, but sync, despite having activity, wasn't valid. I inspected the board again and found a severed trace on the part side. I patched it and that did the trick:

Game fixed.

13 Mar 2019

Strikers 1999 (Strikers 1945 III) - Psikyo 1999 (repair log)

The second board I got from ekorz, or should I call him my friend after the gift he made to me.

Again board had colour issues:

Green was completely absent:

Going back from the JAMMA connector I quickly ended up on a cracked resistor on the final stage of the green colour amplification (33Ω SMD). I replaced it and colours were fixed:

I continued my tests and found left direction for player 1 wasn't registered:

Again starting at the JAMMA edge I found one of the custom resistor array (possibly containing capacitors too) stamped MLR8C4 IAM (or is it 1AM?) measured resistance between pin 2 and pin 3 was ~4kΩ when it should be 100kΩ. I pulled it but the lower resistance between pad 2 and pad 3 was still present. I was left with a single chip in line: a HCT244 (U42), I confirmed the ~4kΩ resistance between its pin 11 (input) and ground. Once replaced all controls were then working.

Game fixed.