(Topic ID: 240447)

System 11 A/C select relay: works but doesn't switch to C power? FIXED

By dmacy

4 years ago


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  • 35 posts
  • 5 Pinsiders participating
  • Latest reply 4 years ago by GRUMPY
  • Topic is favorited by 2 Pinsiders

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#4 4 years ago
Quoted from dmacy:

All flashers work with exception of two by flippers.

Well then the A/C relay is working, if it was not working then none of the flashers would work. You didn't say which flasher wasn't working.

Quoted from dmacy:

I on the right path or is there something else that actually is driving the A-C select other than Q8?

This turns on the relay giving power to the flash lamp bulbs, but you still need another transistor to turn on to apply the ground to complete the circuit.

#6 4 years ago
Quoted from dmacy:

I made it kinda confusing

Let me see if I'm following correctly. A pair of flashers never worked when you got the pin and now no flashers are working.

#8 4 years ago

Looks like you may have unsoldered some 906 sockets. Is it possible you left off a orange wire? All the power for the flashers is daisy chained on the orange wire.

#12 4 years ago
Quoted from dmacy:

But if there was a break, why would they all work if I ground Q8 and run coil test mode and they all work when in A side tests?

Let me see if I'm following you here.

1st. You run a coil test and the coils work but no flashers. Correct.
2nd. You ground Q-8 metal tab and then you run coil test and the flashers work on both the A side and C side but no coils. Correct.

#16 4 years ago
Quoted from dmacy:

Correct on both.

Then your problem is on the CPU board. Do you have a logic probe?

#18 4 years ago

Try this, put the game in switch test. Then remove the balls. Now there should not be any switches showing up on the display. Now ground Q-8 metal tab. A/C relay should click and you should see A/C relay show up on the display. Does this work?

#21 4 years ago

I think DumbAss is on target here. His idea of the opto isolator on the inner connect board, or a bad connection for the switch matrix wires on the inner connect board.

#24 4 years ago

There are some tests that you could do.

You can check the resistance of R-13.
You can jumper pins 4 and 5 of U-1 while in switch test. This should show up as switch #2 C side power A/C relay.
You can check U-1 pin 2 for ground.
You can test U-1 pin 1 for voltage while you ground transistor Q-8 metal with a jumper to ground.
Doing this will confirm that U-1 is bad and needs to be replaced.

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#27 4 years ago

Why don't you remove the interconnect board and post pics of both sides.

#29 4 years ago

Check continuity from U-1 pin 4 to J-1 pin 18.
Check continuity from U-1 pin 5 to J-1 pin 2.
Check continuity from U-1 pin 1 to R-13.
Check continuity from J-5 pin 9 to R-13.

#31 4 years ago
Quoted from dmacy:

I do have continuity to all four of those points.

Something isn't adding up. If there is continuity for U-1 pins 4 and 5 to J-1 of the innerconnect board, and when in switch test nothing shows up when you short pin 4 and 5 of U-1. Then you must have some other switch issues that you are not aware of. There must be a wire break from J-1 of the inner connect board to 1J-8 or 1J-10 of the cpu board. Innerconnect board 2J1 pin 18 goes to CPU board 1J-8 pin 1 and 2J1 pin 2 goes to 1J-10 pin 8.

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#33 4 years ago
Quoted from dmacy:

and as much as I hate board repairs and diagnostics

Hey, this is the best part of pinball.

#35 4 years ago

It was all @DumbAss, he put you onto U-1 right away. I was just along for the ride.

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