how to troubleshoot? Not all of us have trustfunds!

[RFAHL]

Are oscilloscopes really necessary for troubleshooting?  They sure as hell
simplify the process, but come on.... with a little ingenuity, there's ways
to get by without one.

The circuit in question is pretty simple - a bandpass filter that gets
popped  by a pulse and resonates as a result, like a stick hitting a hollow
drum.  The circuit has an input and an output.  If you have other similar
circuits on the board that are working you can tap an input trigger from a
working circuit and pump it into the circuit that's got the problem.  Same
goes for the output of the circuit.  You can use a wire to connect the
output of the "bad" circuit to the input of one of the mixers from a
different section.  Just simple ways to use what's right there in front of
you (and two cents worth of wire).  I've used this type of technique
connecting working satellite receivers to non-working ones to track down
problems. This circuit is far simpler, so I don't see why this approach
wouldn't work.

Couldn't you make a simple logic tester to test for pulses using a simple
LED connected between pulse input and ground?

Also, couldn't you use an audio cable as a probe between the circuit and an
audio amp (with a DC blocking cap for protection), using your ears instead
of your eyes?   

Just some thoughts... it's nice when you have money to spend on tools, but
not everyone's in that kind of position.

-------------------------

ElmacacoX at aol.com wrote:
Ok,  thanks for the many replies guys, but an oscilloscope is way outta my
reach right now.  so, how do I test for faulty op amps, capacitors,
transistors with my little DMM?  the tip on the transistors being two diodes
in a three legged race is a good start for me!

thanks

Eduardo




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