opamp testing?

[nocentelli]

I've suffered a number of inexplicable LFO breadboard failures recently, and have begun to suspect either the integrity of my breadboard, faulty opamps, or my sanity. I know that the usual answer to "why doesn't my circuit work?" is almost always "you did something wrong!", but apart from triple checking connections, there's some weird things happening that make me suspect either the chips, the breadboard or both. Is there a simple-ish method of establishing if an opamp is working? In the course of my most recent failure, I decided to quickly lash together a dead simple fuzz circuit (muff fuzz) to check if the quad i was using was duff. However, I couldn't even get that to work, with the signal dropping right down between stages, and the vref on the non-inverting inputs falling as i measured it... I haven't got much experience with opamp circuits to do informed troubleshooting based on those symptoms like I could perhaps with BJT circuits, so -

Is there a way to check if an opamp is working other than by trying the suspect chip out in a simple circuit that has previously worked?

[GibsonGM]

Short answer: No.
Sorry.

Any basic, VERY simple circuit that uses opamps can be used to test them - the simpler the better...you could make one for singles, and one for duals, for example.    Just something to read the output voltage...1, 2, or 4 test points, if you get the drift.   

If you run it off 9V, you could use something like 1V(DC) for your input, do a X5 gain feedback loop (Vf/Vin), and measure for ~5V at the output, depending on resistor drift.  No need to be fancy.  Do this for each input, depending on if you're making a tester for a 1, 2, or quad opamp.     Worth doing, I think, mainly as you suspect your breadboard.    Be sure to use an IC socket, of course, so you can put them in/take them out!  <he he>   Careful with those pins...

I've never done this, never had to, but always WANTED to have something like a basic opamp amplifier to use for this purpose while troubleshooting PA's and the like.   Give it a try; Ebooks on how opamps work are all over the place....2 resistors for each input, a couple more to set an input voltage, add battery, and done. 

Let us know how you make out!   

[bluebunny]

This, perhaps?

http://www.diystompboxes.com/smfforum/index.php?topic=63394.msg499683

P.S. Google comes up with some ideas too ("op amp test circuit").

[nocentelli]

Superb, thanks - trying it out now.