Quick (faulty?) op amp question

funk1980 · 12th February 2013, 08:50 PM

I'v been tinkering woth op amps for some time now. I think I've got the basics down

.
For some unknown reason, a previously perfectly fine DIY circuit (FX loop signal fase toggle) stopped working. I soon realised there was DC on the output. Turned out to be full Vcc. The three other parts of the TL074 are fine. I checked and re-checked everything, but all seems surrounding circuitry seems fine. Do I need new glasses, or is this a way an op amp can fail??

TANDBERGEREN · 12th February 2013, 08:56 PM

This is one of the ways an OP-amp can fail.

Often also external cirquits need to be controlled for any failure.
If possible, detach any output device at the faulty output of the OP-amp, and try again to power up. If the output of the OP-amp still is at full VCC, you may try to just replace the TL074.

funk1980 · 12th February 2013, 09:06 PM

Thanks. I thought I was going nuts.
It still in the 'bread board' stage, so no harm done to Amy existentie equipement. Is there any reason an op amp woud fail this way?

Enzo · 12th February 2013, 10:58 PM

There is always a reason, but you may never know it. All it takes is a slip of your meter probe, which you may not realize you did. breadboarding generally means a lot of handling of parts, so a static discharge into the part may have happened from your fingters. Oh so many things it could be. There is also something we call random component failure. You may have compromised the part somehow a week ago, and it jut now got around to finally failing. Sometimes ther is an A caused B moment, but most times, it happens and the exact reason is forever a mystery.

When I have an amp with an op amp signal path, and it is not passing signal, in fact the first thing I do is verify the power supply is working then go down the row looking for DC on the output pins.

12th February 2013, 08:50 PM	#1
funk1980 diyAudio Member Join Date: Sep 2011	Quick (faulty?) op amp question I'v been tinkering woth op amps for some time now. I think I've got the basics down . For some unknown reason, a previously perfectly fine DIY circuit (FX loop signal fase toggle) stopped working. I soon realised there was DC on the output. Turned out to be full Vcc. The three other parts of the TL074 are fine. I checked and re-checked everything, but all seems surrounding circuitry seems fine. Do I need new glasses, or is this a way an op amp can fail??

12th February 2013, 08:56 PM	#2
TANDBERGEREN diyAudio Member Join Date: Jan 2011 Location: Fosser, Aurskog-Holand, Akershus, Norway.	This is one of the ways an OP-amp can fail. Often also external cirquits need to be controlled for any failure. If possible, detach any output device at the faulty output of the OP-amp, and try again to power up. If the output of the OP-amp still is at full VCC, you may try to just replace the TL074. __________________ Sooner or later you end up with TANDBERG

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12th February 2013, 09:06 PM	#3
funk1980 diyAudio Member Join Date: Sep 2011	Thanks. I thought I was going nuts. It still in the 'bread board' stage, so no harm done to Amy existentie equipement. Is there any reason an op amp woud fail this way?

12th February 2013, 10:58 PM	#4
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	There is always a reason, but you may never know it. All it takes is a slip of your meter probe, which you may not realize you did. breadboarding generally means a lot of handling of parts, so a static discharge into the part may have happened from your fingters. Oh so many things it could be. There is also something we call random component failure. You may have compromised the part somehow a week ago, and it jut now got around to finally failing. Sometimes ther is an A caused B moment, but most times, it happens and the exact reason is forever a mystery. When I have an amp with an op amp signal path, and it is not passing signal, in fact the first thing I do is verify the power supply is working then go down the row looking for DC on the output pins.