I had a strange adventure today. I was repairing a mixer and plugged the connectors reverse when mounting it together. When i turned the power on it was behaving strange, and i started to smell fried electronics. I switched the power off, reversed the connector to proper position, turned on the mixer once again and... It smells so bad but it works. How come? Can fried op amps still work?
It comes down to what was damaged. It could be some resistor or diode in the circuit is what is producing the smell.
Usually if you smell burnt electronics, something has changed. It could be a resistor changed in value, a diode might now leak, a capacitor may have lost capacitance, or an op amp may now draw a lot more supply current and have higher distortion.
In the end, if you cannot tell the difference, and you cannot locate the exact location of the smell, just keep in mind what happened if it starts to play up.
Sometimes you get lucky, and the effect is never seen.