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Subject: Re: [M]: LX-3 electronics troubleshooting
From: Dave Sage
Reply To: mapug@shore.net
Date: Mon Nov 25 05:50:49 1996

Tom Krajci wrote:
>
> 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.

Depending on the technology used to design the circuit board - sometimes
manufacturers find it necessary to use jumpers to get over trace routing
problems. I think what you describe is a zero ohm resistor (actually
made and sold as such) and used as classy jumpers as described. Use an
ohm meter on it if it is zero ohms on your lowest scale in bothe
directions and it isn't burn't up it is probably a zero ohm resistor.

> 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.

The warm parts are usually connected to if not THE actual problem. I
assume you have tried another transistor?

Also look for a diode directly across the input supply. Sometimes they
are placed across the supply input such that they conduct on reverse
supply and take out the fuse or the circuit board. If the circuit can
take it, sometimes the diode survives but goes short and draws a lot of
current even when the supply is later connected properly.
>
SAGE