• Safe Bally Display Testing

    From Matt Hess@matthess3@gmail.com to rec.games.pinball on Sunday, March 29, 2020 09:17:27
    From Newsgroup: rec.games.pinball

    I have a box of displays with unknown status that I pull from when I need a spare. Last one I pulled must have had a short, and when switched on detonated R93 and cooked U11 on the MPU, and burned R51 on the SDB- which most likely means my HV section is now shorted too (again). This is the board rev with NO 1/4A fuse, but I do have one added in the backbox to try and avoid this scenario (and it didn't blow).
    I'm not sure where the problem is on the display-I do not see any visible shorting- but what a pain in the ass
    My question is, what is the safest way to test displays without putting the rest of the system at risk? I don't want to have to rebuild everything when I pull a dud out of the box.
    Thanks-
    Matt
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  • From bank-a-ball@kghoffman@aol.com to rec.games.pinball on Tuesday, March 31, 2020 18:44:19
    From Newsgroup: rec.games.pinball

    One unpleasant possibility is that the key in your connector has fallen out and you have managed to reverse the connector. That brings bad crap! I had an 8BD once that I used for testing displays. When I brought home over 50 displays from a folded pinball warehouse and tested them, eventually I managed to flip the connector and it was not pleasant. The display fried in a few seconds and there was other hell to pay. Make sure the key is present in your connector.
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  • From pinballdude50@pinballdude50@gmail.com to rec.games.pinball on Tuesday, March 31, 2020 20:57:09
    From Newsgroup: rec.games.pinball

    I would say that there was a short for sure. I've had fires too when I test bally displays.

    Since you have multiple boards, just put them safe by side and meter them out.


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  • From MAC in Indiana@google@mcwhorters.net to rec.games.pinball on Thursday, April 02, 2020 05:28:32
    From Newsgroup: rec.games.pinball

    If you are going to have a test system that uses the production system boards, you need to augment the original non-robust designs by inserting some protections in-line between those boards and you unit-under-test. I hear about people frying dozens of chips on WPC boards when they test a sound board which has a short and ties 12v to the 5v... ouch!
    The key protection to add is over-voltage protection. Each voltage supply should have a "crowbar" circuit added that will clamp the voltage and not allow a short to a higher voltage to back-feed into your test fixture.
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