HK tuner fm signal breaks

Stink Bear

Active Member
I'm working on a Harman Kardon TU615 tuner.It started out as a power problem - no dial lights. I got that fixed but now when playing it breaks the fm signal very briefly, sometimes often, sometimes just once in a while. It seems to do it more when I first turn it on, and it seems to be worse on certain frequencies (lower) / stations. When it happens the signal meter LED's go out sequentially and the fm stereo and QZ lock lights go out.
I'm fairly new at troubleshooting and most of the units I've worked on were receivers with amp problems.
I believe this is in the fm tuner section. I have some ideas on how to isolate to a particular stage by looking for a signal with an o-scope but I'm not too sure about that, and if I can isolate to a stage I don't know what to do from there.
Any suggestions would be appreciated.
 
I've done some more troubleshooting, I believe I've found that there is an IC in the IF amp section that is bad. If I turn off FM muting the music continues, the lights still go out temporarily.
I've decided not to put any more time into this tuner, I don't think it's worth it.
 
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