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Dead Marshall Blues Breaker Mk1

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Re: Dead Marshall Blues Breaker Mk1

Postby Wonks » Thu Jul 18, 2019 3:48 pm

Folderol wrote:Yes, same for all of them, it's a check for leakage more than shorts, but the actual values you get will also show up O/C resistors or a wonky chip.

Oi! Leave my chips alone and get your own! ;)
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Re: Dead Marshall Blues Breaker Mk1

Postby ef37a » Thu Jul 18, 2019 4:38 pm

I am with Will, op amps rarely fail and you can easily bugger the print.

An op amp will have its output pin at 1/2 supply within a few mV . If not check the input pin voltages.

You can get a pretty 100% test of an op amp by hanging a meter on the output pin then using a resistor of about 10k (+ or - 100%!) take the inverting and non-inverting pins in turn to either -ve or +9V . The output should move accordingly. I use a wet finger but only do that for battery power!
Not likely any danger from a wall rat but no point in chancing it.

If you are really sure an op amp has failed, chop each pin in turn then remove the bits by heating and banging on the bench. DON'T try to pull them out, that way damage lies. Clean up with solder wick.

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