(Topic ID: 274200)

System 11A troubleshooting solenoid 4A-C (C locking on)


By dmacy

5 months ago



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  • 4 posts
  • 2 Pinsiders participating
  • Latest reply 5 months ago by dmacy
  • Topic is favorited by 1 Pinsider

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#1 5 months ago

Issue: On Fire!, I have an issue with my solenoid 04A and C. The coil and the corresponding transistor Q24 get very hot.

But some background: Machine was fine before i did anything. I swapped out the playfield and noticed the issue after fire up and found that I had the left down coil wires swapped. I corrected them and added in a new diode to be safe. Coil tests 5.2ohm which is same as right down coil using same part number so believe they’re ok.

Replaced just the TIP122 with a 102 as it tested bad. Same issue so noticed resistor R49 (68 ohm) was burnt and predriver transistor NPN 2N4401 tested bad. Ordered them to replace them as this should be the fix!

Today: 68 ohm and 2N4401 replaced and the issue remains. I ended up cutting the coil out and took the thick leads and wired them together. Tested again and the transistor doesn’t get hot whenever the 4C isn’t firing. So I’m led to believe the issue isn’t the 4A down coil but likely upstream in the circuit.

I’d like to work this out myself with some help on here. It seems like it should be obvious. I had LED’s in the C side and cut the 330ohm warming resistors Cut but put in incandescent and out the 330’s back in. They still don’t flash and stay lit whenever any C circuit is lit.

Am I missing anything or should I be checking something else? Pics below are be for the predriver and resistor were replaced.

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#2 5 months ago
Quoted from dmacy:

So I’m led to believe the issue isn’t the 4A down coil but likely upstream in the circuit.
I’d like to work this out myself with some help on here. It seems like it should be obvious.

I think you have already stated the direction you should go ... "upstream". Try looking at U20. You can do a static diode test on the IC to look for an obvious problem. If you have a logic probe you can check the digital logic signal is behaving correctly during solenoid test.

#3 5 months ago

Thanks DumbAss. Friend who can take this further will be diving in deeper for me. He can get it back. I’ll update when he gets to it.

1 week later
#4 5 months ago

You called it dumbass it was bad U20 that took the hit. My friend 80spit socketed it and replaced it and working great.

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