pinbot system 11 coil stuck

robotype

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ok when I start a game or enter test mode the top bumper (special solenoid) will be energized and stays on. so I replaced tip122, 2n4401 and 7407. nothing changes. before replacing the PIA I thought to post here for some suggestion. oh yes if I remove the connector with the blue wires the solenoid won't be activated.
 
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I might be dealing with something similar. I'm down to the 7404 and the PIA myself. It's the lower pop bumper for me on a Taxi. Waiting on the 7404 (or was it 07?, I forget, whatever it is, it's on the way).
 
ok as soon as I start a game or enter test mode the top bumper (special solenoid) will be energized and stays on. so I replaced tip122, 2n4401 and 7407. nothing changes. before replacing the PIA I thought to post here for some suggestion. oh yes if I remove the connector with the blue wires the solenoid won't be activated.

Is the switch stuck closed?

You can also test through the driver circuit with a logic probe rather than just replacing everything.
 
Is the switch stuck closed?

You can also test through the driver circuit with a logic probe rather than just replacing everything.

no the switch is ok in the test mode. I probed both ttl before but I can't figure out where the problem could be as (in test mode) all the pins from the 7407 were red except pin 12 and it's the line for the faulty solenoid so I replaced the ic but on the 7402 are all green including pin 5 which goes to the solenoid acting strange, anyway I will replace the 7402 as well.
 
7402 replaced, problem not solved. as soon as I enter game/test mode 1J19 pin 9 will be grounded even if switch matrix inputs are disconnected. should I go for the PIA @ U51? not sure what to probe on the PIA to check it...but I think it could be the only cause at this point, or is there something else I could check first?
 
I might be dealing with something similar. I'm down to the 7404 and the PIA myself. It's the lower pop bumper for me on a Taxi. Waiting on the 7404 (or was it 07?, I forget, whatever it is, it's on the way).

does yours get energized when you switch on the game or when you enter test/game mode?
 
does yours get energized when you switch on the game or when you enter test/game mode?

The latter. I've been dealing with this on and off and I think I may have missed something on the MPU in the switch logic. The line for the problem pop is getting pulled low by something while the other two are staying high.
 
The latter. I've been dealing with this on and off and I think I may have missed something on the MPU in the switch logic. The line for the problem pop is getting pulled low by something while the other two are staying high.

exactly the same! do you think it could be the PIA (U51)?
 
Here's what I would have done before replacing anything:

Note: The upper pop bumper on Pinbot is driven by special solenoid #6. These instructions are for that circuit but the logic applies to all the special solenoid drivers.

Start by disconnecting the coil that's stuck on when in a game, if you have not already. Put a meter across the wires going to the coil. It's better to troubleshoot with a meter than a coil.

The solenoid only energizes when you start a game so we know it's not a shorted driver or pre-driver transistor. If either of those were shorted the coil would energize as soon as you turned the game on. The first thing to look at is the stuff hanging off the switch side of the NOR gate in the pre-driver circuit.

Logically you could split the circuit in half at the NOR gate. One side comes from the switch and one side from the CPU via a PIA and some logic combining it with the blanking signal to basically "turn on" the circuit. The switch side also has a PIA output connected to it so the CPU can drive the circuit when it feels like it (like test mode). The CPU "turn on" side seems to be working because the coil is only energized when you start a game so the switch side seems shorted.

The first thing to do is eliminate the switch as the source of the problem. Remove the connector coming from the switches. If your problem goes away you know either the switch is stuck closed or there is a playfield wiring problem.

If that doesn't solve the problem I would look at C74 and ZR7. If either of those shorted you would see the problem you're having. Check pin 5 of U50 with a logic probe. It should be high. I'm guessing in your case it will be low. Desolder one side of both C74 and ZR7 and check again. If it's high now then either the capacitor or zener diode are shorted.

If pin 5 of U50 is still low it's time to check the path back to the PIA. The PIA pin controlling that driver circuit is pin 39 of PIA U54 (CA2) but it also goes through a buffer (pins 12 and 13 of U49.

If pin 12 of U49 is low and pin 13 is high then the 7407 at U49 is probably bad. If both pins are low then it's time to test the PIA.

As usual, confirm all this stuff with the schematics. I'm making this stuff up as I go, not just copying it from somewhere else :)
 
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Could be. But I plan on following Lindsey's troubleshooting when I work on it next. I'll post when I figure it out.
 
'twas the Zener for me. I haven't plugged the board back in yet, tryIng to fix my display problem, but my switch line is no longer grounded.

Thanks, Lindsey.
 
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zener for me too!! ZR7 like you said Lindsey, thank you so much!! I printed your troubleshooter and it will stay in my pin*bot manual forever...ooooh canada
 
zener for me too!! ZR7 like you said Lindsay, thank you so much!! I printed your troubleshooter and it will stay in my pin*bot manual forever...ooooh canada

Happy to help :)

That's actually really cool. When I first started working on these things I printed out all of Clay's stuff. It's nice, years later, that someone wants to use my ideas in the same way. That's what keeps me trying to learn even more.

Also kind of shows a trend in those diodes failing. That's good to keep in mind for future troubleshooting.
 
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