Simple opamp tester

[sshrugg]

Did a little searching out of curiosity.  I've had two build attempts where I can't find any mistakes.  After checking things like crazy, and debugging for days, it turned out to be bad opamps.

http://tangentsoft.net/elec/opamp-tester.html

That might be useful to some of you.  I haven't tried it yet, but I plan on building one.  If anybody has other ways of testing opamps, post them here!

[cpnyc23]

I've been thinking about something like this for a while now... I'm not really a fan of the 'put it in working circuit' method of testing op amps...

I wonder how it would be possible to build one that has sockets for multiple DIP cases (8, 14, 16-pin).  Or would one need to be built for each kind of amp and pinout?

-chris

[O]

I'm not really a fan of the 'put it in working circuit' method of testing op amps...

How come?

[petemoore]

I'm not really a fan of the 'put it in working circuit' method of testing op amps...
  The only non-circuit test I can think would be of any use is checking to see if all the pins are intact.
  You could remove some parts from a gain stage [for instance the DC blocking in/out caps] and have a slightly simpler circuit which could be used to test only DC bias.
  I've had good results with field testing opamps, I've only managed to fry a few, and all the others provided performance consistant with their data sheets..of course I didn't scope them, but trust many others have.
 

[mdh]

I'm not really a fan of the 'put it in working circuit' method of testing op amps...

How come?

Perhaps because that method can be pretty subjective, depending on the nature of the "working circuit" being used for testing?  A simple go/no-go tester such as the one linked by the OP is desirable to have around.  I remember having breadboarded that very circuit at some point in the past, but I don't remember if it detected any bad op amps.

[cpnyc23]

I like the go/no go idea b/c I think it is a simple tool for a simple job.  I'd rather throw a chip into a testing device and verify it before firing up a circuit for the first time and see an LED give me the go-ahead.  Otherwise you have to build the circuit, have it not work, pull the chip out, open up another pedal & put the chip in, plug in the guitar and test.  That is a lot of steps.

Necessary? No.  Just personal preference is all.

-chris

[scratch]

If you can find it, Poptronics, Nov. 2001 has an OP-Amp and Comparator test circuit, go/no-go test, single , dual 8-pin pkgs, 14 pin and 4136 layout quad pkg.  LM339 comparator.

[spudulike]

http://www.headwize.com/ubb/showpage.php?fnum=3&tid=5768

[cpnyc23]

scratch - thanks for the tip

spudulike - thanks for the link!

-chris

[scratch]

I'll try reconnecting my scanner to my PC and see if I can't scan the magazine article, only 3 and a half pages long ...

[cpnyc23]

That would be really appreciated scratch - thanks!!!

-chris

[sshrugg]

http://www.headwize.com/ubb/showpage.php?fnum=3&tid=5768

I like this one more.  I think I'll build it tonight.  Thank you!

[scratch]

couldn't get my scanner to work on my own system, but still managed to scan the article last night ...

The files are large 209K up to 510K.

http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/OPAMP_tester_1.JPG.html
http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/OPAMP_tester_2.JPG.html
http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/OPAMP_tester_3.JPG.html
http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/OPAMP_tester_4.JPG.html

[cpnyc23]

Wow!  That looks like a really cool & useful project - thanks for taking the time to scan and post those Scratch - above and beyond.

-chris

[scratch]

I've been thinking of building that myself for a while, but been busy with other (non-stompbox) digital things so haven't had a need, but there have been times where I wondered if my OP-amps were working ...

As long as it's usefull ...

[sshrugg]

Hey!  Thanks everybody for throwing in on this.  Much like I expected, it became a pretty cool thread with quite a few options.  Thank you!

[grapefruit]

Hi,

I wouldn't really trust the first two circuits shown. Usually when an op amp fails the output is slammed up against one of the rails. If it's the positive rail then the LED will light up anyway.

For a simple tester you could use a circuit similar to the one shown. Use a single 9V supply, arrange the op amp as a buffer or non inverting amp with a gain of say 2. Use a pot as a variable voltage divider to go to the non inverting input of the op amp. As you turn the pot toward +9V the LED gets brighter. The same pot could be used to feed all op amp sections.

Stew.

[sshrugg]

It seems like none of these would work for testing CA3080's.

Does anybody have an idea for those, other than "throw 'em in a working RossComp"?