Today we have some new PAL dumps from these PCBs:
Got a Rabio Lepus (japanese release of Rabbit Punch, a cute shoot ’em up released by V-System Co. in 1987) in lot of faulty PCBs.Hardware is made of a CPU and a VIDEO board:
Board had a graphical issue, sprites were splitted and misplaced:
Usually this kind of problem indicates an addressing fault so wrong address are generated hence wrong data are read/written.Sprites data are stored in six devices (four 27C256 OTP ROMs and two 28 pin 1Mbit MASK ROMs)
Reading them gave good dumps but the logic probe revealed that address line A7 was stuck high in all of them (address bus is shared)
Tracing this address line back lead me to an output (pin 19) of a 74LS273 @8A, the corresponding input (pin 18) was floating.All the other outputs were active (generating the other address lines for sprite ROMs) and inputs were toggling too.Each input is connected to a data line of a near 2k x 8-bit static RAM @10A so following this logical arrangement I figured out that pin 9 (data line D0) of the RAM should have tied to pin 18 of the 74LS273 but it was not so :
I restored the connection with a jumper wire and this fixed the issue:
As I expected, doing a visual inspection on solderside revealed a severed trace:
End of job.
Today we have some new PAL dumps from these boards:
All dumps have been successfully tested back on respective PCBs using GAL16V8 targeting devices.
Got this X-Men PCB for a repair :
As often happens on Konami boards that use hybrid audio module (the ‘054544’ in this case) audio was horribly scratchy and loud:
Electrolytic capacitors had already been replaced with same type but this obviously was not enough:
So, I removed the module from PCB and decided to fully service it:
I replaced with new parts the 4558 OP-AMP (I used a compatible LM358) and the AD1868 DAC as well:
At same time I reinforced some poor connections :
Lastly, as icing on the cake, I varnished with black laquer :
As always I do, I installed on PCB a couple of 1.778mm female round machine-tooled strips.This was the final result:
Time to test :
Job done.
P.S.
For the uninitiated, the ‘054544’ module has been reproduced, you can read more about on these threads:
Some months ago I received for a repair this Tatsujin Oh PCB (known outside Japan as Truxton II)
As you can see from the above picture, the custom ‘HK-1000’ (used for inputs) in front of JAMMA edge was missing but this was not the main problem, board won’t sync up:
All the graphics and video timing signal (HSYNC, VSYNC, etc..) are generated by a large surface mounted ASIC (208 pins QFP package) marked ‘GP9001’:
You can find its pinout on page 32 of the Knuckle Bash schematics:
https://www.jammarcade.net/files/Schematics/Arcade/Knuckle%20Bash.pdf
The IC was previously reworked by someone in a bad way, many pins were bridged together, flux residuals were not cleaned.So I decided to remove it :
and solder it again:
Happy with the result I powered up the board again and I was greeted but this static garbage screen:
Probing the main 68000 CPU revealed no activity on data bus.Doing a visual inspection of PCB I found a couple of severed traces on solderside just around the CPU area:
Patching them allowed the board to boot but, obviously, due the lack of the ‘HK-1000’, the game was stuck on a ‘TILT’ error message:
Input check in TEST mode reported ON most of them :
Now some words on the ‘HK-1000’.As said, this custom handles all inputs and it’s has been adopted in later Toaplan PCBs.There are two revisions of it, the early one has a ceramic package and due this nature it’s very prone to damage and failure.This revision is used on Truxton II/Tatsujin Oh and FixEight:
The newer revision is more robust and it’s used on Ghox, Pipi & Bibis:
Back to repair, from available info it seems the functions of this custom can be reproduced using a couple of 74LS240 (actually the custom handles also the coin counters and lockout but we can omit it), this is not a suprise for me since a lot of previous Toaplan boards use same design with these TTLs (see for example Truxton, Wardner, Hellfire and other).Doing some tests with a single 74LS240 I was able to successfully map some inputs turning off the TILT error
This allowed me to enter in game :
Later, owner of the board installed the missing HK-1000 and confirmed the board was perfectly working after my repair:
P.S.
I’m currently drawing schematics for the replacement of the HK-1000 and I will post here my results.Stay tuned.