WPC-S High Voltage Repair Question

troxel

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I posted on RGP, but thought I would try here, too.

My +62 wasn't working and therefore displays were blank. Bought a kit
and installed it. Problems was d3 had corrosion on it and ate some of
the trace. I connected it to r4 and q2, and when I put it back in r4
immediately burnt. I double checked all parts and orientation and
everything looks good. Any advice one what to double check?
Thanks!
 
Sounds like there's a short somewhere. Unfortunately, if a trace was messed up somewhere it could have also taken out more than just the obvious component. The thing to do is get the schematics and a continuity tester and try to find out what's wrong.
 
Found the schematics and found that the base of q10 isn't connected to d3/r4 (burnt track). What's the best way to jumper this?

Just not sure what to use since the voltage is higher. I usually just use kynar wire, but would guess that's too thin?
 
Found the schematics and found that the base of q10 isn't connected to d3/r4 (burnt track). What's the best way to jumper this?

Just not sure what to use since the voltage is higher. I usually just use kynar wire, but would guess that's too thin?

First verify that there is a trace that's missing. Or is it a thru-hole that has a broken connection? I'd use thicker gauge wire and do the jumper on the underside of the board.

Here's some video of work done on a DMD board, typical process of going over things and double-checking everything.. http://pinballhelp.com/fixing-a-dead-dot-matrix-display-board-part-1/ It also demonstrates how easy it is to put in a component wrong and fry stuff - things like transistors will come in groups with different pin configurations even though they look identical.. you have to double check everything before powering things up.
 
Good link. Thanks for sharing. It's a burnt track and not a through hole crack. I will hopefully get it back together in the next couple of days, and try it out again. Thanks for the help.
 
Had a chance to look at this again today. My +62 was around +30.

I ordered the 120 Ohm .5 Watt resistor, and hasn't shown up yet, so I used two 220 in parallel. Would this cause the problem if it's 10 ohm difference? If not, any other spots to check?

I'll look over the +62 section again with the schematic.

Thanks.
 
Had a chance to look at this again today. My +62 was around +30.

I ordered the 120 Ohm .5 Watt resistor, and hasn't shown up yet, so I used two 220 in parallel. Would this cause the problem if it's 10 ohm difference? If not, any other spots to check?

I'll look over the +62 section again with the schematic.

Thanks.

I can't comment on that mod not knowing the details of the circuit. Did you pull the resistor and verify it was malfunctioning?
 
Resistor was cooked and measured about 67 ohms. The schematics call for 120 ohm, and I didn't have one. Figured that 110 was close enough, but could be wrong?

Went through the board again and not seeing anything out of line.
 
many resistors aren't better than 10% anyway. if the tolerance band is silver, it's a 10% resistor, if it's gold, it's 5% - there are better ones, but most you see commonly are either 10% or 5%. so 2 220's in parallel is probably a good enough match for the 110 until the one you ordered comes in.
 
Thanks, Elfyhead. That's what I was thinking too. Any guess one what would make the +62 go around 30 volts?
 
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