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Subject: Re: PCB problems please help

Date: 12/04/01 at 1:03 PM
Posted by: Darren
E-mail: darren@guartel.com
Message Posted:

In Reply to: Re: PCB problems please help posted by Russ Kincaid on 11/30/01 at 9:27 AM:

Thanks Russ, I tried a freezer spray but this didn't work as the cct board just frosted up! So I fashioned a piece of steel to the right shape, popped it in the freezer for half an hour and then touched each component in turn. Alas it was a transistor in the feedback path, although only rising by a couple of degrees C. This transistor only passes very small current and is wired as a diode (NPN). However I used a discreet alternative thus raising it off the board and it works fine. Many thanks.
Last question: I have a connector that connects a coil to form a resonant circuit. The signal is a sine wave, 22kHertz, 2-5v pp, 2.5V dc offset. When the circuit is running, touching the connector case will effect the resonant circuit. The case is isolated from the pins. Also the same can be said for the 9V battery that is also near by. I need to know why this is happening and how to cure it. It doesn't happen on all samples, just some.

Cheers Darren


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