I got this Data East Robocop pcb from a friend that was totally dead.
I had more Data East pcb’s around so I could test the bottom ROM board with one of those CPU boards and it was also not working. So I started pushing the EPROMs in their sockets and after that the game booted up.
So now I tested the ROM board with it’s original CPU board and game booted but the screen was almost completely black apart from some graphical elements like the energy bar.
After visually going over the CPU board I found that one of the custom ASIC L7B0072 had a crack in the center of it.
I had a broken Midnight Resistance board (not the previous repair) that had this ASIC, so I opted to transplant it over to the Robocop board.
I noticed that the top of the ASIC had a brownish discoloration, but I didn’t know if it was toast or not, so I desoldered it with my hot air station and soldered it onto the Robocop board.
Confirmed that there were no shorted pins on the ASIC and booted the game, but unfortunately the transplant did not help. Some graphics appeared, but mostly scrambled characters and when coining up and pushing start, the game reset. (forgot to take a picture)
After having a conversation with caius (thanks again for all your advice) we opted to do another transplant but with a better looking ASIC.
Redid the procedure, hot air station to remove the ASICs and then soldering again and lo and behold, the game has good looking graphics once again 🙂
But I quickly noticed that there were no audio at all. Using my audioprobe I found that there were music been generated by the YM3014 at 4M and FX from the YM3014 at 3M and then going to the OP-AMP 3403 at 4N
Nothing came out of the 3403, so I eventually found that there were no +12V input on pin 4 of the 3403. Checked the JAMMA edge and found a broken track. I guess that the operator had some form of voltage measuring device and somehow broke the track at some point. I soldered a little metal wire to bridge the gap and booted the game again.
Now audio could be heard for a short second and then silence again.
I eventually found a shorted capacitor at
After replacing the capacitor the audio was loud and clear again. Job done 🙂
The Konami ‘056820’ is a custom IC in SIL package (13 pin with an unusual 2mm of pitch) used on GX System hardware:
Sometimes it’s wrongly reported to be an RGB DAC but if you look at his pinout (from Lethal Enforcers II schematics) you can understand it has a different function although always related to colors generation :
Its particular feature is that it gets extremely hot and may fail as a result.Here’s a picture taken from the net where the coating literally melted due excessive hot:
Driven by a curiosity I decided to take a look inside:
The biggest component in the upper left corner of the above picture is a Toshiba TA78M05F fixed voltage regulator, datasheet here:
It provides on its output the +5V (regulating from +12V) to nearby custom ‘056766’which is actually the DAC (specifically it powers the analog section of it since digital one takes the +5V from JAMMA connector).This explains why the part gets burning hot since the radiating surface of the heatsink (actually the copper of the PCB) is too small and not adequate in my opinion.All other parts are SOT-23 PNP transitors for amplify the RGB channels, capacitors (for decoupling and voltage regulator stability) and printed film resistors, in particular there are thre 75Ohm ones to bring the RGB signals to the standard impedance level.The custom was pretty easy to reproduce, the only precaution I took in design was to enlarge the heatsink surface on the footptint of the voltage regulator.I used an MC78M05 in DPAK package since the original part is nowadays obsolete :
The Konami ‘054573’ is a custom chip found on various PCBs from this manufacturer : Bucky O’ Hare, Metamorphic Force, Gaiapolis, Xexex, Mystic Warriors, Wild West C.O.W. Boys of Moo Mesa to name some.Technically speaking it’s a RGB DAC (one for each color) which converts into analog the palette data bits received from the the custom ASIC ‘054338’. There are no schematics showing it but it should be a 9-bit DAC .
It comes in the usual SIL package (15 pin) covered by black coating like many custom with similar functions :
I have partially covered this topic in a past repair from mine, where you can see also picture of its circuitry inside :
Being a important and not long reliable part I decided it was time to think of a replacement.No particular difficulties were encountered in identifying the internal parts, tracing connections and developing a PCB which arrived from my manufacturer after some time.Here’s the reproduction finally assembled and installed :
Some years ago I came across to a Rolling Thunder PCB where the custom marked ‘130’ was replaced by a small sub-board (don’t know if made from Namco or bootlegers, from manufacturing I presume the latter)
It seems the original custom is used only on Rolling Thunder PCB where, indeed, you can find it marked as ‘130’ in form of a DIP40 IC:
Whereas on schematics it’s shown as ’41’ like in Metrocross and Baraduke PCBs but it’s not the same and changes from game to game (the custom is basically an address decoder for generating the memory map which, indeed, is specific to a certain game)
After some time I sold the board but before doing this I took a couple of high-res scans of parts and solder side of this replacement PCB with the intention to reproduce it someday in a modern way.That’s what I successfully made recently :
I hope this will help to repair our Rolling Thunder PCBs with a faulty ‘CUS130’ as it seems it’s a quite prone to failure part.