I recently puchased a non working Firepower. The game didn't boot with original boards in, so i installed a spare Rottendog 327 MPU/driver combo.
The game worked perfectly, probably played 30 games on it. At the same time, i had purchased a Tri Zone project (non working), so put the Rottendog combo board in it, and it worked fine for a few games.
Then i put the Rottendog combo board back in Firepower - after resetting the board to Firepower, the game booted fine, started a game and after plunging the ball, i am 99% sure that exactly when it hit the top left pop bumper, the game died - all lights out and it took out the solenoid fuse on the power supply board. I also smelled a light electrical smell from the rottendog board, but couldn't visually see any damaged chips, or feel any that were hotter than others. The board then wouldn't boot.
NOTE: I did not do anything else to the Firepower while the board was in Tri Zone, so it appears to be a very unfortunate coincidence it happened after the board swap. I also triple checked the plugs and their positions and am quite certain i got that correct.
So i sent it off, along with the original MPU and driver boards for repair. All boards were repaired, for interests sake, the following was replaced on the rottendog board:
Replace 2 x 74hct08 chips , 1 x 14 pin socket , 1 x 74hct240 chip and socket , 1 x 74hct10 chip and socket , 1 x 74hct244 chip and socket , 1 x Uln2803 chip and socket , 1 x 6821 chip , 1 x crystal.
Received all boards back, and installed the orignal CPU and Driver in the machine. I did notice there was a coil firing every couple of seconds - the same coil and i am fairly sure it was one of the kickout holes, so assume a switch may have been a bit sticky. I power cycled the machine and it booted fine a 2nd time, no coils firing and added credits. Plunged a ball, and again, am 99% sure it happened exactly when the ball hit the top left pop bumper, machine went dead, no displays, no lights and a buring electrical smell from the CPU area. I have attached pictures of the wiring - as i really made sure i had the plugs installed correctly, referencing this page: http://firepowerpinball.com/downloads/BackboxWiring.pdf Now the machine has both LEDs locked on upon power up.
So now i am quite frustrated, obviously quite a few $ down the drain in repair costs as twice it appears there is another problem that is taking out parts of the CPU board. I am aware i might be focussing on the top left pop bumper a bit too much, but am fairly convinced its either related to when this coil fires, or maybe when any coil fires?
After inspecting the top left pop bumper, i saw nothing unusual visually. However, i did find 2 things;
1. The top right (not left which is appearing to be the problem one) pop bumper coil had the signal wire fallen off - it doesn't appear to have shorted on anything the way it was hanging - or had a previous owner cut this wire off? - I don't think this is the case as i don't recall it not working when playing the game previously, but i can't be certain
2. Using the capacitor test on my multimeter, the top left pop bumper capacitor on the switch tested quite differently (sometimes 1500, other times 1 - 10) to the other 3 caps on pop bumper switches that all consistently tested aroudn 130 nf. All 4 caps appear to have been replaced by a previous owner and are 22uf 63V electros
I tested the coil diodes (snipped a lead) and they were all fine, along with coil resistance being around 4.3-4.5 ohms on all coils.
So i am starting to think the cap on the switch may be the culprit, however am unsure if this failing could cause such problems on the CPU? I am also very cautious and unsure about how to test anything, as i really don't want to keep frying my boards, paying for repairs and 2 lots of postage! I do have the repaired rottendog board i can use for testing. I will also replace the wire off the top right bumper coil, not sure if this is related or not.
So long post, but do you think i am on the right track with replacing the switch capacitor of the pop bumper, and is there any way of testing without taking more boards out - or are there other checks i should do? Or, could the problem reoccur when any coil fires?