(Topic ID: 251092)

Lamp Matrix issue - please help

By jrawlinson_2000

4 years ago

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Latest reply 4 years ago by herg
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I hate matrix issues I never have any luck (idea) on how to fix them.

So I have a BSD and the 'R. Ramp 2 Million' lamp is lit when any of the others are also on in the same row, most of the lights if not all are boards so the diodes are on PCBs is there an easy why to try and diagnose what and where the issue is?

I did try a multi meter on the power board pinouts but I guess I need to use a probe, so another question is; (as I have a probe) how do I use it and check the power boards pins to see if its a cabling or power board issue?

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Check solder joints on pcb. I had issue once where someone repaired on and the solder was touch pin next to it. It would fire off the other adjacent row light.

Try this with power OFF to see if you have a shorted transistor.

Measure resistance from the tab of Q83 thru Q90 to either the board screw or to the ground braid. From what I see on my Corvette, all these transistors have high ohm reading.

If Q83 is measuring quite a bit lower ohm reading than all the other 7, then disconnect J133/J134/J135. If you have the same low ohm reading on Q83, then the transistor is shorted on the board and needs to be replaced. If the short went away, then you have an issue under the playfield.

As an update;

I had to pop in another power board to fault find another issue whilst in I tested the lamp matrix issue and it was no longer an issue.

So its a power driver board issue I bet transistors.

Thanks for your help folks.

Even with the board out, you can test from the transistor tabs to the board ground to see if one is shorted.

What @pinballmaniac40, says. If it is the transistor, I would expect all rows to show the same issue, though. So, Dracula Face on with all of row 7, etc.

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