Help. My Whirlwind System 11 is having solenoid trouble on the 25V side first noticed at the shooter lane solenoid not popping the ball up.
After some troubleshooting, I do not have 25V supplied to the solenoid, peaks up to about 5.6 and then drops back to ~0. The whole (brown wire) circuit has this low issue back to the F2A fuse affecting four solenoids.

If I measure the voltage on the 25VDC "C" side at F2C I see a constant 35.6V. On the rest of the 25VDC circuit after the 25VDC Supply (At W6, F1 and F3) I have the same 35.6V. On the 50VDC side I see 74.9V consistently through the circuit, before and after the A/C relay, but the 50V "C" side is not used.

I disconnected the J11 and the J4 connectors to take the coils/playfield out of the circuit and test the board. There was no change to the measurements above.

So I suspected the A/C relay because everything looked right up to the relay. When power on and am in game play I can hear the A/C relay constantly cycling and again the F2A voltage fluctuates significantly as the relay cycles. I purchased a replacement Auxiliary Power Driver board from Marco Specialties thinking this would fix the problem. It didn't; I have all of the same issues with the brand new board.

I cant understand why part of the A/C multiplex relay would function and not others.20181122_083033 (resized).jpg

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I have checked continuity through the connectors as best as I can. Everything shows good continuity through the F2A and F2B from the board to the solenoids.

I also disconnected J4 and J11 to remove them fro the circuit and still had the same result at the board.

I went to test mode to fire the individual coils. When in test mode the brown wire shows a constant 39.6V on all 4 coils (and I don't hear the A/C relay cycling). 1A, 5A and 8A coils all work in test mode. 2A still does not.

I followed the Voilet/Red wire from coil 2A back to the Auxiliary Power Driver Board and have good continuity Back to 5J4-8 on the Aux Power Driver Board. with J4 disconnected at the board, that pin has pretty flaky readings showing a drifting <1V whether it is firing or not. That's different from the other pins, but I'm not sure if its significant.

After I saw the brown wire was at 39.6V in test, I tried the circuit again in game play. Setting my meter to MAX, I measured 39.6V all over the brown wire in game play. I think my meter is too slow to display the 39.6V with the A/C Relay firing.

Based on all of that I think I was running down the wrong path with the low voltage thing. I think that the issue is isolated to whatever fires Solenoid 2A. According to the prints, 5J4-8 is the pin that fires the Solenoid 02A. 5J4-8 ties to 5J1-7 on the Aux Power Board. My prints show a Solenoid 2 going from a 5J1-7 to a 1J11-3 at the main MPU so I'll start trying to backtrack there and check continuity, etc.

I'll get back on it tonight and see what I can find.

If everything shows continuity back to the MPU I am not sure what I can do from there.

One more note, I did test the 2A coil by jumpering over to the Violet/Brown wire on the 01A coil and it fired repeatedly without issue. I also changed out the coil just to be certain and had the same results.

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Putting it in test mode I have narrowed it down to just solenoid 2A so I have not tested removing 1J12. I can still do that if it helps.

The brown wire goes from 8a to 5A to 2A to 1A and everything is really solid and good continuity to every coil.

Im suspecting something in the Voilet/Red wire so am planning to check that all the way back to the MPU tonight.

Ok, voltage checked good all the way back. 39.6V at 5J4-8, 39.4V at 5J1-7, 39.1V at 1J11-3. Since there was a slight voltage drop, I thought that maybe there was just a strand of wire somewhere so I:

1. Jumpered from the violet/red terminal on coil 2A to 1J11-3. The coil did not function in 'test' or in game play.
2. Jumpered from 1J11-3 to ground and the coil fired immediately (twice).

I think that this means that the wiring and connections are good between the Violet/Red terminal of 2A coil and the CPU board. So it has to be in the CPU? Or is there something further I can do / look at?

Sorry, I have several bulbs out and just assumed this one was too. I didnt think through that 2c would be relevant.

I grounded the metal tab on Q25 and nothing happened. I'm not sure what a cracked header solder joint is so I'm not sure what to do with that.

I noticed that Q25 was hot to the touch when I tested it and I have a thermal camera so I took a picture. Q25 and U20 (feeds Q25) are the only abnormal hot spots on the board by almost 100F. Man you are good! The peak temps are 177F in this image.

If I need to test Q25 in the board, can you give me direction on that one? I am afraid of poking around in the main CPU with power on and making something worse. Should I somehow test U20 also or is it likely that the Q25 problem is causing U20 to get hot?

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Sorry GRUMPY I was wrong. I had plugged 1J12 back in so the A/C relay was on. I unplugged 1J12 and tried again. This time coil 2A fired. Sounds like Q25 is bad then?

Thank you for all of your help Grumpy!

I'll order the spares from Marco. Looks like they don't have the 1N4003 for D-2 but they do have a 1N4007 rated for 1A-1000V. I will order it but likely wont use it since I just replaced the Aux Power Driver Board with a new one, I don't think that this is it.

I'll post back when the parts arrive and let you know how I turned out.

I got the parts and replaced them. Pulling the old transistors proved pretty challenging; its been 20 years since I had circuits labs.

Q21 and Q25 did it. Whirlwind is back in business and the kids and I are back to loving it.

Thank you Grumpy!