NAD 4150 problem/parts

[ericrhenry]

Sorry if this is the wrong forum. I have a NAD 4150 tuner that I pulled out of storage to use as an RF signal detector for testing continuity of long coax cable runs (I had an HP RF signal generator at the other end). (Any flames for low IQ gracefully accepted :-)) Some other large signal (possibly even 60 Hz line) snuck on, after which sensitivity of the signal meter is seriously trashed, and I can't get any demodulated audio out when passing in an FM-modulated signal even in the millivolt range. I initially thought I might have damaged one or more of the RF stages, but lately I'm thinking the LA1235 IF chip might be at fault (because of the meter problems, at least). Anybody have any thoughts about this, and if it's not a totally bizarre idea, any suggestions about where I can get a single replacement for this (fortunately socketed) chip to test the idea out?
Many thanks in advance,
Eric