Quoted from mdhawkeye:Refurbing a Firepower I bought a few weeks back. It's my first pinball, but I've done several other similar projects (jukebox, helped my son on a Blackout, etc) so am somewhat familiar with the workings. The credit knocker solenoid was toast...completely fried, dark brown and the knocker stuck in the sleeve. I'm assuming in a past life the sleeve got dirty, the knocker stuck and burnt out the coil. Replaced the solenoid and still nothing. When I pulled the driver board, I noticed the trace for the solenoid (#14-> pin 4 on SJ9) was totally burnt out of board...YIKES!!!! I replaced EVERYTHING in the path of that circuit...the resistors R68, R69 and R70, and the transistors Q40 and Q41. I used a tiny jumper wire to go from the emitter of Q41 to pin 4 to replace the trace. So far I've blown 3 TIP122 transistors. I figured the first was sloppy soldering on my part, the second I pulled because it was getting REALLY hot during the solenoid test, and the third sparked and cracked in half during power up :-O I tested voltage as best I can with a digital multimeter coming out of the resistors and the Q40 BEFORE Q41 and all seems to be in spec as best as I can tell (hard with DMM in the back box...suggestions welcome). Voltage off of pin 4 all over the map again because of my tools but off the emitter of Q41 when I can reach it seems correct, between 32-35V. I know the ICs in the path are doing the correct thing (used a logic probe to see that they were pulsing properly). I've looked at most wiring coming from board to molex, and molex to knocker and dont see anything obvious. I'm kinda lost now, and would appreciate the expertise of those who have been here before.
Thanks
Andy[quoted image][quoted image]
When these transistors are burning, is the knocker firing?
Do not solder the jumper wire between the pins of the transistor. Scrape the solder mask off the remnants of the burned trace, directly above the transistor. Leave the leg of the new transistor long and bend it towards the center of the board, following the old trace. Solder the long leg to the old trace and the patch wire to the long leg.
Power up the board with the driver board connector that runs to the coils removed and see if the transistor still burns or over heats. If it does, you have a problem with the board.
While you have the connector removed, measure the power to the knocker coil and make sure you have power connected to the banded side of the coil. The other wire on the coil runs to the connector on the driver board you have removed.
If all this checks, and the transistor does not burn up with the driver board connector removed, turn the game off, re-connect the driver board connector and turn the game on. If you hear the knocker energize, quickly turn the game off. This means the coil is still locking on and we need to troubleshoot further.
mdhawkeye
Casper, WY
