Some days ago I had on the bench this Wolf Fang: Kuhga 2001 PCB (known outside Japan as “Rohga – Armor Force”) , a good-looking horizontally scrolling shoot ’em up manufactured by Data East in the 2001 :
When I powered it up, I was greeted by this screen.
It was a clear lack on SYNC signal confirmed also by a measurement with a frequency counter on pin 13 solderside of the JAMMA connector.So, given the absence of schematics, I started to trace back the signal with a multimeter but couldn’t find where it was generated.Visually inspecting the board I found a suspicious crack over a trace :
My multimeter confirmed the trace was really severed.After patching it, the SYNC signal was restored but there were jailbairs on the sprites:
Sprites are stored in some 42 pin MASK ROMs :
I visually inspected the area and found another broken trace on solderside which lead to a data line of these MASK ROMs:
I promptly patched it with some AWG30 wire:
and sprites were restored:
But after this I realized that sound was missing at all.Diverting the audio signal to an external amplifier, I could hear both music and sounf FXs but there was no output from the TA8205AH amplifier on PCB :
So I decided to remove and replace it but , as for my previous Pitfall II repair, I was wrong, it was good.Looking at its datasheet, I could figured out how its mute circuit was made:
Checking the 220uF 16V electrolytic capacitor connected to pin 8 of the amplifier gave me a dead short across the terminals.So I desoldered and test it out of circuit having confirm it was really shorted:
I was recently sent an Asteroids PCB which I had previously bought back from the dead, the PCB had developed distorted vectors but still running.
Here is what the TEST screen looked like, the actual diamond shape was perfect but text was oversized and distorted;
The actual GAME mode looked worse;
Check out the giant asteroid!
I knew the problem was in the Vector State Machine (VSM) area, specifically the area which is responsible for handling object vectors, so I looked there first.
It was not long until I found a decoder (LS42) at 7E which seemed to have some pins stuck LO;
I desoldered the decoder;
I tested the decoder in my IC tester;
I then socketed and replaced with a fresh decoder;
I dumped the specific PAL present on a Konami X-Men 6 Player revision.Board has in total three PLDs, two are in common with the 4 Player version and they were already on our database while this one was unique.
Lastly, I dumped four PLDs from a Funky Jet PCB, board has six devices in total but two of them were registrered.All dumps have been successfully tested on GAL16V8 targeting device.
Some years ago MikeJ from FPGAARCADE made a 28 pin CPLD replacement that could program to replace certain custom chips from a variety of arcade games and even the Commodore 64 PLA.
While I was waiting for Mike to get another batch of his boards ready, ColinD on the UKVAC forums contacted me telling me about his own project.
The concept is essentially the same as Mikes but his was originally geared towards replacing the SLAG chip on some Atari games. It does however have multiple links available so it can be configured into what we call ‘normal’ mode. This makes it so the power pins are in the corners like with ‘normal’ chips/EPROMS/etc. It also has space for a 3.3v regulator so a XILINX XCR3064XL CPLD can be used in place of the EPM7064 that I’m using.
My first project for this was to reverse the Konami 501 custom chip. Luckily I have a one of the bootleg versions of Time Pilot here courtesy of Muddymusic that has the same layout as the original board but all the customs are implemented in TTL on riser boards so reversing this was a matter of drawing out the schematic.
I eventually got something that let the game boot and work but there were some graphics faults here and there. This ended up being an issue with using a modern part to replace old parts. The propagation delay on the CPLD is a lot less that the original TTL part. This was solved by enabling the ‘Slow Slew Rate’ option in Quartus II.
So with the 501 reversed and the chip I have confirmed working I’ll set about doing the others on this board.
I’ve yet to test them on genuine hardware but I remain hopeful.
