Dumb Luck & a little common sense

By undrdog

April 03, 2020

55 days ago

Someone sent me a plasma display that worked the last time he'd fired it up, but it was dead when I got it.  Some of the resistors on it looked really burnt.  One looked like the solder was broken.  I don't know much about electronics, and have only been soldering since I bought the machine.  Figured it couldn't hurt to take a resistor (didn't even know it was a resistor at that point!) from the display I was replacing,  and put it into the dead one that used to look good. 

Got the resistor off the dead board ok.  Broke the one from the display I had.  It looked pretty bad, anyway.  Wondered if I could use a resistor from somewhere else on the display I had.  Looked it up in the manual, learned it must be a resistor because of the big R, and sure enough, there were several of the same ones.  Pulled one off, soldered it onto the new board.  It was one that someone had already put on as a replacement - it had long leads and was fatter than the rest.  Looked newer, too.

Wasn't sure which way to put the new one on, but either it doesn't matter or I had a 50/50 shot and got it right by chance.

Fingers crossed, I put it in the machine.  Digits 1, 2 & 4 lite up and look great. 

It was dumb luck that the resistor I decided to replace was even the problem on the board at all.  It just looked bad.

Now I can read that guide that shows how to track down problems or just start replacing resistors that look bad until the whole thing fires up.

Anyway, I'm kinda proud of myself for getting this far by dumb luck and a little common sense.  Because I don't know anything about electronics.

Thanks for listening and letting me have this little brag on myself.

Keep safe & keep flipping!

- undrdog

PS It isn't such a great idea to have your pinball machine at work.  Mine is at work, because that's where I have room for it, but I sure would play it a lot more if it was home.  Its kinda lonely going up after work or on weekends to play it in an empty building.

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53 days ago
Got the hundreds digit working, by replacing the resistor next to the first one. Replaced the resistor on the third one, lost it all. Probably too much solder shorted something. Tried unsoldering most of it, still dead. Need a small point tip for my solder iron. And probably thinner solder.
49 days ago
Make sure the resistor is lined up the same as the others. What I mean is that there are different colored bands and make sure that you insert the transistor to match the others. If there’s an orange band on one end and a red band on the other, and the other resistors are installed with orange toward one edge of the board make sure your new one is lined up the same. It won’t work correctly or at all if you install it backwards.
39 days ago
Didn’t know that! Thanks!

Using resistors from other displays and a lot of advice from Pinsiders, the display now looks brand new!

If I’m going to keep working on circuit boards, I’m gonna need a magnifier and a better set of teensy pliers.

Next project: replacing the volume pot.

In other news, I’ve replaced the bullseye drop targets with the explosion pattern, which is more correct.

Probably fixing to have to rebuild the flippers. One needs a new coil, at least.

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