Ok, let's answer some questions, though at this point I'm pretty sure I saw the answer I was looking for, so I AM indeed an amateur who doesn't know his op-amps (an idiot, basically)...
Are you sure grounding both inputs produces a valid output? Something flakey with your breadboard? Power on wrong pins or hooked up backwards? They don't normally die sitting on a shelf. Operator error?
Unfortunately I don't have a scope to see exactly what the output is doing, but with my DMM, it just sits there at 0v.....mocking me....
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/xfacepalm.gif.pagespeed.ic.EBDwh1hCfo.png)
I went as far as to measure continuity directly on the Op-amp itself to make sure the pins are actually making contact all the way to the end of the corresponding wires and they DO, plus it doesn't explain why it worked the first time.
I THOUGHT I might have done something wrong with the first chip, indeed but why the others too ? I power the breadboard from my bench supply through a DC-jack, so polarity can't possibly switch, unless I move jumpers around, which I didn't, so that's not it either...
Then:
just to clarify. where did you buy these opamps ?
today fake world of even simple electronics components is wider as you may think...
We buy parts from TME, so there's no doubt in my mind they're genuine TI parts, although for such a basic and low power application I'd expect even the cheapest, worst, disgusting knock-offs off Aliexpress to at least swing from one goddamn rail to the other ! I wouldn't trust power electronics or precision stuff indeed, but this is too basic an application not to work !
Then:
Did you use a diode to catch the back-EMF of the relay coil.
Absolutely, plus that's the very first thing I did when I noticed it's no longer working: disconnect the output from anything else, so that's not it.
However, THIS:
The LM383 are open-collector - they don't actively turn on. You need to add a pull-up resistor to Vcc to make it work.
This indeed is the answer I mentioned and it made me go oooooohhhh......so THAT explains it ! Ok, THIS actually makes sense and I had a look at the diagram and the 393 indeed can't swing positive, only to GND, so this is definitely it and I was measuring it all wrong
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/xfacepalm.gif.pagespeed.ic.EBDwh1hCfo.png)
However, it doesn't quite solve the whole mystery and doesn't explain what happened to the bunch of 833s and whey they seemed to work the first time....I couldn't have killed them one by one as I tried them on the breadboard...............couldn't I ?
![Cheesy :D](https://www.eevblog.com/forum/Smileys/default/xcheesy.gif.pagespeed.ic.KPzuH4J-TG.png)
I even made sure to discharge myself
![Cheesy :D](https://www.eevblog.com/forum/Smileys/default/xcheesy.gif.pagespeed.ic.KPzuH4J-TG.png)