Repair 9 - I bought a MPU3 board off ebay which was sold as ‘probably not working'
which translated from ebay speak to English means shagged!
The good news is that it
boots up with photo/reel drive. So far so good. (Just green/red and power)
With the
blue plug in...
The program is a rebuild and doesn't switch off bad transistors so
I get a stuck lamp drive traced to T33. (It was red hot) which makes things easy,
just replace the hot transistor.
With the white plug in the payout slide is stuck on, put the meter on the slide (not
the common) and trace stuck slide back to white plug pin 13. Replace T3 and TC3 and
that's sorted that.
Again, this program doesn’t spin the reels on start up so reel errors don’t show up until the start button is pressed. When started the reels spin but alarm, no photo. The photo diodes don’t light – looking at the schematic, photo diodes are switched by T55 – replace T55. Diodes are back. All 3 faults done. Board runs OK.
Repair 10 - Next board, missing lamps 1 column of lamps missing (8 bulbs out). Find the common line to all 8 lamps with the meter on the lamp holder, trace to the blue plug, follow the pin on the blue plug to the bad transistor. Traced to BU12 lamp drive, replace transistor T28. Fault is fixed.
Repair 11- Next board, battery not charging, Magik got this one off the bat, bad transistors T60 or T61, replace both transistors. Battery now charging, you can actually see it come up 0.1v every second or so. Fault is fixed.
Repair 12- Next board, board was working fine, then for no reason the sound went really quiet, you could just hear it, but very faint. Checked speaker and speaker pot which were all good. Changed T11 which sorted it.
Repair 13- Next board, Missing reel drive, board boots into attract but no reel spin. Photo diodes come on, but no reel spin. Missing 50hz pulse at IC18 pin 12. Fault traced to D44. Also replaced R85 and all components in the white power plug area (all resistors and diodes). They get very hot and burn up.
Repair 14 - This board was working when the machine went into the garage. Now it boots up, but then starts counting down in hexadecimal. Change RAM. Problem solved.
Repair 15 - Next board, no 5v at regulator and capacitors in poor condition. Board is corroded and has some battery damage. Completely rebuild regulator pcb, 3 new caps, new regulator, new triac. 5v is back. Problems around D44 and D45, missing 50hz pulse. Repair both rectifier diodes, but still not right, replace R85, but still can’t see 50hz pulse. It’s at IC18 pin 12, so the 555 is good, but no joy. More to follow on this repair. For now it’s on hold.