I have a Onkyo TX-8211. It's become unresponsive to both the factory
remote and a universal remote that was programmed to control it. I
popped it open to inspect the receiver module. I couldn't see any
markings on it (without removing it from the pcb, anyway). I measured
5V on the supply line. On the output line I could see a digital signal
that was about 120mV peak-to-peak when I sent an IR signal from one of
the remotes.

Anyone know if this is typical of the output? Should the signal be
larger? If the module needs to be replaced, how would I identify a
replacement?

Since it is generating a signal I'm wondering if some other part has
failed. There's an electrolytic cap wired to it, which I'm eying
suspiciously.