Don't you hate it when you try to help someone out and end up making things worse?

Tried to help out a fellow pinsider by showing him how to adjust the leaf switches on the slingshots. Got them adjusted, but now row 8 switches aren't working right. I don't know how well they were working before -- that may be why I thought the slingshots needed to be adjusted -- but they aren't working at all now.

When I test the switches I get notice that all of the row 8 switches have a ground fault.

I disconnected the white wires from the slingshot switch and all of the other switches on that row - with the exception of the slingshot of course, and the right magnet opto work correctly. When I connect the two wires (but don't connect them to the leaf switch) the test immediately shows a groundfault, then shows that the last switch operated was the opto. (I should have tried connecting just the one power wire to the switch to see what happened, but didn't think about it. Will try this tomorrow.)

So I am thinking that the problem HAS to be with the opto, correct?

Can anyone tell me:

A) Am I on the right track with the diagnosis that the problem is with the opto?
B) If the opto is shorted, is it possible that it is the opto itself, or does it have to be a wire or connector to the opto?
C) How the heck do you get to the back of the playfield to even work on it?

Thanks for your help!!!

Chris

LTG,

If I pull the connector off the pins it comes up with a check fuse error.

I don't see how it can be a board problem. If it was board then nothing on row 8 would work at all, but as I said, if I break the row 8 partway down the chain, the other items on row 8 work properly.

Chris

LTG,

It does say check fuse F114 and F115. But it ONLY says this when the J209 connector is removed.

When the J209 connector is plugged in it does not have the check fuse error -- just a ground fault error.

When the two white wires are removed from the slingshot leaf switch, the ground fault goes away and everything on Row 8 works correctly with the exception of the Right Magnet Opto and, of course, the slingshot - since it is not connected.

I would buy the U20 if nothing on Row 8 EVER worked.... but the fact that it works as long as one or more of the switches are isolated means that the board is working correctly, doesn't it?

Chris

Thanks markmon... I caught that too, that it should be U19, not U20.

I did try the dmm on it. Looked for continuity between wire 9 on the J209 connector and the ground braid. Tried it at a few different switches and couldn't get continuity -- of course I couldn't reach to the rear opto to try back there, and the resistors might be preventing continuity anyway.

I just feel like it HAS to be a physical ground somewhere, but I can't find it.

Coz, thanks for the heads-up. I will take a look. You say under the first switch.... Do you mean the first switch on the matrix...? The right inlane switch? Or do you mean the first switch the ball trips when it goes up the right ramp?

Thanks for your help guys. Still open to any suggestions!

Chris

Thanks coz. Will take a look at that tomorrow. Thanks.

Morning bump.

Okay, it IS an opto problem, (kinda)!

Have it isolated to the 16 optical board. I have continuity between the R8 pin and the ground pin.

So what does this mean? Easiest, I'm sure would be to replace the whole board, but it is $75 and no one seems to have them in stock.

How can I go about figuring what on the board went bad. It might be as simple as replacing one or more of the $1.00 U Chip Quad Comparitors.

Suggestions!!!!!?????

Thanks!
Chris

I *think* it is the U5 chip. I tested all of the chips and U1-4 all test the same, but U5 has absolutely no resistance between the ground lug and 4 and ground lug and 7.

Gonna try and de-soldier and install once the kids are in bed. Picked up a socket and a new LM339 at R-Shack tonight.

This is my first attempt at board-work. Wish me luck (Especially since it isn't my board!)....

Chris

Well, I am happy to announce that my first board soldiering attempt went well... sort of. Meaning that I didn't make things worse.

Unfortunately, I didn't make them any better.

I removed the U5 LM339, installed a socket and replaced with a new LM339. The problem is exactly the same. I still have a grounded J5 pin 8.

NONE of my diodes test bad. If NONE of my diodes test bad, it HAS to be in one of the other LM339 chips, doesn't it? Is there any way to find out except to take each one off of the board and replace it?

Can anyone suggest any test I can do to isolate this problem?

Driving me insane....

Chris

doctor_pinball

Thank you. That is interesting.

I think my next step will be replacing the LM339s on the Opto board. Can you tell me which two you replaced? I was thinking of starting with U3 and U4 since the seem to be controling the Row 8 optos.

Thanks!
Chris

It ended up being a bad LM339 chip on either U3 or U4 (I can't remember which one) on the Opto board. I had a 50/50 shot and just ended up picking the right one the first time (Well second time..).

Learned a lot in the process, mainly that the best way to do de-solder a chip is with a bulb, not with a wick. I nearly burnt up the board (literally) in my attempt to get a chip (the wrong one, ironically) off of the board. Went tonight and bought a bulb and what took me two hours last night, took 15 minutes tonight.

I'm going to share my words of wisdom (in my experience only)....

If you have a problem with a switch or a lamp, don't immediately assume that it is a problem with a chip on the main board. Three times now I have had weird matrix problems - two with lamps, this one with the switch. Each time the immediate suggestions that I got were to replace the chips or other piece on the main board. Each time that would have not solved the problem.

1st lamp problem: Wire connected to wrong lug of lamp - not isolated with the diode
2nd lamp problem: Had a phantom trace in one of my lamp boards - had to scratch it out
Switch problem: A short in a chip on the opto board (granted this one was a chip problem, but not the chip that was suggested I replace.)

Eliminate everything else first, if all else fails, THEN look to your boards -- don't start there.

Thanks to everyone who offered suggestions and support. Sometimes the best part of this forum is bouncing ideas back and forth. Taking the time to think about it while you are writing often solves a lot of problems!

Chris

Yeah, that Hakko looks sweet. But I think I will stick with my $12 Radio Shack Special....