The board that came with Gold Mine wasn't working and had numerous faults. Nick has asked for the solutions to the problems, so here goes...
The initial faults were stuck lamps and constant 10p coining causing an alarm when 50 credits was reached. Often the boards with the most faults are the easiest to repair because you can actually see what the fault is. It's ones that freeze and reset that are the bastards to sort.
As always start with the reg caps, I now use 63V for all 3. It saves time buying different value caps. 63v only because I could buy them cheaply in bags of 20.
Next change the RAM. I do this anyway as it's nearly always bad.
Next change T60 (which fell apart in my hand) and T61. Ram voltage transistors. (238 and a 510)
Then run board and see what happens.
The lamps are messed up, some are lit when they shouldn't be. So try and run the board with blue plug out. It will play but it still coins to 50 then alarms.
The lamp transistor area has been worked on before and some of the repair work looks suspect. The resistors that have been changed are quarter watt and should be half watt. So change T28-T35 and R34 to R41 (2.2 ohm half watt) and all the diodes IN4148.
Run it again. Now the coining problem has gone, but I still have 3 stuck lamps.
I don't know why this should fix the coining problem? Any ideas?
I meter transistor T12 to T26 and one is shorted. It's T16, so replace that.
Now it will run and all the lamps are correct.
Nearly there. No 10p pay out. Trace it back from the slide to transistor T3 and triac TC3. I replace both and TC4 breaks and falls off, so that's done as well.
Now it seems OK and it's running. This board will burn out the power plug so an extra wire has to be fitted to take the load off the ground pins. It's a faff, but if you don't do it the white power plug will burn out and the machine won't run.
Paul
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