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Subject: [M]: LX-3 electronics troubleshooting
From: Tom Krajci
Reply To: mapug@shore.net
Date: Fri Nov 22 05:18:17 1996

Help! I blew the electronics in the board of my club's LX-3 by
reversing the polarity when I hooked it up to my car battery. I've
since replaced all semiconductors that may have failed but it still
won't work. Both motors still work (when I give them the proper
voltage from another power supply), and the step up transformer is
still fine.

There is one "mystery device" on the board that I can't identify, and
haven't replaced. It's the size/shape/lead pattern as a 1/4 watt
resistor. . .but it's colored gray with only one thin black band on
it. This band is like a reisistor color band but it's in the very
middle of the device. This device is connected to one of the pins of
a small transistor. What is it - a diode? It's not like any diode
I've ever seen.

When I power up the board it draws so much current that the power
supply drops to about 50% of no load voltage. No signs of shorts,
solder brigdes, smoke. One TIP 30 transis gets warm to the touch.

Any advice on how I can troubleshoot this board. Typical voltages I
should see at various places, etc. would be a big help!

Thanks in advance,

Capt Tom Krajci
B-52 Intelligence Officer
"In God we trust, all others we monitor!"
http://spur.barksdale.af.mil