Sudden Rat Death

[Fleetdog]

A coworker brought me his Proco Rat today to have a look at.  He has had it for years with no problems then one day, he said he plugged into it and he got just a second of sound then it died.  No sound since.  I opened it up for a quick peek and I see no obviously broken wires or charred components.  Has anyone had experience with this sort of thing who could give me a likely first place to start looking.  I figured I would first use a multimeter just to check resistor values and idle voltages (if I can remember enough from school to calculate a few from the schematic).  Failing something there, I thought I'd try to build a simple audio tracer. 

Surely someone here has a better idea than this plan and I'm all ears. 

[yertle]

I would start by taking a look at the ic and transistor voltages first using a multimeter. Then get yourself an audio probe and start from the beginning of the circuit to the end to see where the signal 'stops'. good luck.

[petemoore]

Has anyone had experience with this sort of thing who could give me a likely first place to start looking.
  Yes, take a look at the debugging page [~top of threads], it outlines the information necessary to do 'effective' debugging...when visual inspection and dwiddling fail, this is the place to start completion of the debugging tasks..

[Fleetdog]

Well, that didn't take long.  The lightbulb went on and I realized that this pedal is true bypass but we aren't getting any sound no matter what you do to the switch.  I ohmed the switch and found that the output side of the switch never has continuity between the throw and either pole.  Defective switch.  Should be an easy fix. 

I did look at the debug thread (briefly) before posting but it seemed to be directed mostly towards a new build that isn't working versus an old pedal that has worked for a long time.  I was looking mostly for components that are likely to fail over time.  I should have worded it better in my first post.

[frokost]

The debug thread, Geofex: http://www.geofex.com/fxdebug/fxdebug.htm and the audioprobe. Should take care of most things.

[Processaurus]

yes, the carlings they use are worthless.  Had to replace mine as well.