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I have an EPOCH MPU board that probably gone south, although I'm not 100% certain. No, i'm not just going to replace it as thats what everybody seems to do, then throws the old ones away which is stupid as these are going to become rarer and rarer. Simplified problem: The machine boots (partially) and most of the lights go in to demo mode, and reels attempt to move. But nothing more. Now for the techy bit. The problem in detail Power supply was buggered to start off with, as there was no -12v rail, which turned out to be a faulty cap whos ESR was way way way off the scale. I also replaced all of the caps on the board while I was there as some of them were a little bit suspect after 20 years. This stabilized all of the rails some what and got rid of some excess ripple that would never have helped. I also discovered a fault resistor, well at least what i thought was faulty anyway, R20 in the PSU which is the drop from the 240v mains power in to an opto-isolator via a dioide, was burnt and I was unable to ascertain the exact value. I believe that it is meant to be 100k, but I can't be sure as the colours were burnt off! This will adversely effect (and this is where I am guessing now) the sync pulse and/or the line power sense which could be the fault, but without a diagram or such, its difficult to say. The MPU board battery had burst, no surprise. It has destroyed a multitude of tracks, and taken a surface resistor and generally made quite the mess. Once the PSU was sorted, this board wouldn't boot properly and only three lights would show up. I repaired all of the broken tracks, replaced the surface mount resistor and cleaned up everything checked and double checked. The board now lights up correctly with top to bottom lights as follows. ON, OFF, ON, ON, ON, PULSE. The game then boots as described above. So I scour the web for a manual, diagram, schematic and none can be found, well the one I did find is in the maygay manual and is of such poor quality that I can't read it! The serial output lines have data on, and appear correct but again need more info on output pulses! It would appear as if the FPGA is not being programmed correctly on boot, as ROMS 2 and 3 are not being accessed. Chip enable should be pulled low and they are not, BUT this could be normal operation as we are only currently in demo mode. ROMS 0 and 1 are enabled and AFAIK are outputting correctly. This could just be a partial boot problem or it could be a dead FPGA, i am not sure. All of the pins on the FPGA test as per the Datasheet, but its a little ambiguous. The 16MHZ crystal is oscillating perfectly with a beautiful sine wave so no issues there The bottom line is, I know that I can repair this board, but I NEED a schematic or a better quality copy of the maygay manual. Or alternatively answers to some of the queries! Just to recap, R20 in PSU - What is the value? SYNC Pulse - What frequency/amplitude? Pink cable - Currently outputting a sine signal of aprox 4.7v, is this correct and again, frequency/amplitude? MPU - Are all roms accessed simultaneously? I will keep working on the board, as being able to actually REPAIR these rather than replace, would be eternally useful to all. So If any one has any info, it would be of great help. Thanks, Jody
