Check the drive transistor on the auxiliary power board. That would be a TIP36C.
(Topic ID: 277256)
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1 month later
Quoted from brainmegaphone:is this part of the special solenoid switch circuit? If so could a switch be locking on causing the coil (and ultimately Q1 and R1) to burn out? Or am I on the wrong track here?
No. It is not part of the special solenoids. The special solenoids are 17-22. The catapult is 3A. It can be referred to as a switched solenoid but it's switched in the sense that the CPU drive transistor Q32 is switched between the A or C side not the solenoid being triggered by a playfield switch. The word switch is being used as a verb in one instance (switching between power sources = 3A) and a noun in another (triggered by a switch = 17-22). Curse the English language.
Quoted from brainmegaphone:A little more troubleshooting tonight - the coil that fires the catapult is not shorted nor burnt as far as I can tell. Normal resistance compared to similar coils and I note that the coil sleeve comes out normally telling me the coil is not getting hot or being left on. Not to mention when it burned out last night I would have noticed if the catapult had been stuck up. Switch for catapult also seems to be working normally.
The coil is specified as 23-800 and that should be around 3.9 Ohms (from memory). If the solenoid is shorted you should blow a fuse for sure and possibly damage the transistor due to the excessive current. When you test the resistance you should ideally isolate the solenoid. You can probably just pull the drive wire connector on the interconnect board to isolate it.
Quoted from brainmegaphone:I did test the transistors on the MPU again and they test fine and do not appear to have blown when Q1 and R1 on aux board blew. Despite that I can't help but wonder if the MPU (which has battery damage repair) is somehow intermittently causing a problem that results in Q1/R1 on the driver board to burn out. I'm stumped.
The drive transistor on the CPU board is Q32 and that's in the lower left corner (where all the other regular solenoid drive transistors are). It's almost as far away from the corrosion zone as you can get. That's not to say that corrosion cannot affect it but it's a low probability.
Quoted from brainmegaphone:Would you guys do anything else when replacing Q1/R1 on aux board again? Anything else I should test/check?
I should also mention that (oddly enough) D3, D33, D34 all test fine as well. I don't know what I should be looking at. Help appreciated.
The only thing I can suggest to try putting an explicit diode across the solenoid.
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