Wisconsin Pinball

Hey guys,

Looking for some advice on my next step. Restoring a Black Hole. As I mentioned in a previous post, I'm having issues with the coil that resets the lower playfield 4-drop target group always being on. Here are the steps I've done so far:
-Gottlieb ground wire mods
-Rebuilt the power supply board
-Repinned the A3-J1 connector between the MPU and driver boards
-Replaced the power transistor and secondary transistor that drives the coil on the driver board
-Checked the switches on all 4 of the drops

When I first started troubleshooting this, it would happen about 4 games in. Now it happens almost immediately when launching the 1st game. Thinking it has to be some kind of a short and all my dinking around has made it worse. I'm about out of ideas on anything else would cause that coil to always have 44V driving it. Any ideas on my next step? I've plum run out.

Scott

Check the input voltage to the driver transistor just to rule the transistor out.

Thanks John. Are you talking about the +5V between R57 and the ground at R58? The circuit in question is Sol.5.

http://www.scribd.com/doc/223467608/Got ... ion-Manual

Page 26 has the Driver Board schematic.

Coil and/or diode Ok? Wiring harness not pinched anywhere? Doublecheck your re-pinning work to be sure a trace didn't get ripped. Heck, doublecheck all your work. I know I've ripped my fare share of traces!!

Keep at it and good luck!!

I'm on my 2nd coil, so one had to be good at one point or another. This thing gets hot! Troubleshooting sooner or later bubbles the sleeve. Good call though, I think I just need to go thru the relevant wiring harness and look for a pinch. Thanks Tully!

All righty then....feeling very happy and kind of dumb at the same time. I have resolved my stuck drop target coil issue. Turns out the problem was the 2N3055 power transistor after all. I had already replaced it and the feeder U45 transistor. Both read fine on the dmm in-circuit, but since there was nothing else to replace with just the 2 transistors and 3 resistors in the circuit, I went ahead and replaced it again. Bingo!!! Played about 30 games on it and the drops on the lower playfield are working just fine. Speculating that when I replaced it the first time, I didn't have one of the mylar washers and perhaps either the Base or Emitter pins was making contact with the housing (Collector) and shorting it out. Then the short wasn't there when I pulled the board out to test it again without the tension of the connectors. I'm going with that. At any rate, happy camper.

Next step...replacing the grinding spinner motor. We're getting close Mark.