26 Sep 2018

Mutant Fighter - Data East 1991 (repair log)

Game took very long time to boot, then would play extremely slow, sometimes hanged, sometimes played overspeed for a second, and also had no sound. Otherwise board was in very good condition like it's never been operated:

I started by troubleshooting sound issue. First obvious thing I noticed was sound RAM @ J24 was a shiny one. Piggybacking a known good RAM on top of it restored sound. I replaced it and that was all that was needed in the sound section.

Then the second issue regarding speed of play, hanging, overspeed. Quite weird. I probed main CPU (68000 CPU in a custom QFP package marked '59') for a dodgy RESET or CLOCK signal: nothing to mention here. Then I found by touching a specific area of the board on the solder side I could get the game to play at correct speed for a second, and by doing so every second I could have the game playing normally. I thoroughly inspected the area and found a factory defect: one of the leg of the LS74 @ K3 wasn't soldered. I had the impression that by applying pressure on it game would play fine.

I resoldered it but nothing changed. Thinking the chip could be bad and not having the possibility to test it on board with my logic comparator because of it being SMD, I took the decision to replace it: no dice.
To me there was clearly a floating signal somewhere and by touching the concerned trace/pin with my hand I could restore the connection or at least drive the signal to a state where the board would be happy with it. I quickly found a floating trace, that lead me to an other LS74 @ J5. This time chips seemed soldered properly but by using my magnifying lamp I could see one of its legs was covered in solder, so as the associated pad but there was a really tiny crack in between. I tried to reflow the leg but solder was stubborn and didn't want to adhere to it. I had to add quite a big blob of solder for it to adhere on both the leg and the pad:

This time game played normally:

Game fixed.

21 Sep 2018

Sega System C2 multi kit - part 2

After assembly it was time to test the boards I routed:

Before installation ROMs IC4/IC31/IC32/IC33/IC34 must be pulled and jumpers JP5/JP7/JP17/JP18/JP19/JP20 must be set to 2-1.

The 2 boards fit like this:

Program (& graphics) romboard:

Sound romboard:


Et voilà!

Everything works as expected!

12 Sep 2018

Neo Geo AES - SNK (repair log)

This console has been donated to me (well I had to pay shipping from the US which was huge!) as not working after a failed BIOS mod. I've seen failed BIOS mods before but that one was awful...
The person who attempted it for sure didn't have the appropriate tools and after what I think was a long struggle, managed to pull the original BIOS, ripping many traces in the process. Then, as holes weren't cleared properly, they chose to solder wires between the motherboard and a DIP40 socket:

And tried to patch some broken traces on the solder side too:

After realising it was a complete fail the board was used as a donor, one of the work RAMs has been pulled, and of course a pad has been ripped and few others lifted:

Admitedly I was quite disapointed. I cleaned the case the best I could and sent the motherboard to the scrap pile.
Many days later I went back to it, long story short and as suprising as it seems, I don't own an AES anymore so I found motivation to accept the challenge.
First, and out of curiosity, I checked the patching wires: 70% were good, 20% were absent, 10% were wrong.
I removed the bodge, cleaned the area a bit and cleared the holes:

I installed a socket:

Did the trace patching work on the solder side:

Then installed a new work RAM and patched the missing pad (incredibly other lifted pads survived the soldering):

Finally installed a UniBIOS (V3.3). It looks much better now:

All connections in the BIOS area checked good, so as work RAMs.
Time for a test.
We have a Neo Geo splash screen with the jingle playing!

Title screen of the game (sorry, only cart I have):

Everything works as it should (graphics, sound, controls):

Console fixed!

6 Sep 2018

Sega System C2 multi kit - part 1

After having hacked all Sega System C2 games to bypass security protections I had the idea of designing a kit to support all the games on a single motherboard.

As System C games (3 of them) are fully supported on System C2 I also included them.

That's a total of 14 known different games (plus 3 vending machine romsets, not really games so not included):
- Bloxeed (System C)
- Borench (System C2)
- Columns (System C)
- Columns II (System C)
- Ichidant-R (System C2)
- Poto Poto (System C2)
- Puyo Puyo (System C2)
- Puyo Puyo 2 (System C2)
- Ribbit! (System C2)
- Stack Columns (System C2)
- Tant-R (System C2)
- Thunder Force AC (System C2)
- Twin Squash (original rotary stick version) (System C2)
- Zunzunkyou no yabou (System C2)
And I also added my Twin Squash hack:
- Twin Squash (joystick hack) (System C2)

I went for a very simple approach: big EPROMs with bank switching logic and game selection by dipswitches (a header connector for connection of a remote dipbank is also included).
The System uses 2 independent ROM banks:
- one for CPU code, graphics and music
- one for sound samples
Then I drew the schematics and assembled a prototype (of course it was a bit messy with hundreds of jumper wires).
Due to the C2 board layout I designed 2 boards interconnected with jumper wires:

And tested all the games successfully:

At that point I was very satisfied by the results and decided to route PCBs:

Which came in the mail few weeks later:

Stay tuned for the next part ;)