McIntosh MAC. 4100 Receiver FM tuner right output weak

[firealley]

HI FOLKS,
I have a Mac 4100 that has an issue with the right output only when it's on FM. The sound is very weak and scratchy. Left side output is fine. This is an intermittent problem... Works fine for a while , then cuts out for a while. All other functions work fine continuously. ( phono 1&2, Aux. AM all work fine and mono function is fine. Any help and suggestions are well appreciated.

 

[firealley]

 

[firealley]

Quick Update... I had read a 5 year old thread, which talked about removing the Amplifier and Decoder cover and checking for loose connections. So I removed it (twice now) and each time I remove the cover the FM channels work perfectly. (equal in stereo) when I replaced the cover the first time ,after a while the FM problem returned. I'll monitor this closely this time. Any thoughts? I know this situation sounds weird and might not make sense, but it is true.
The cover that I removed is posted in the previous post.

 

[arcsound]

Did you leave the cover off the 2nd time, so you can tap components with a dowel, to see if there is any mechanical sensitivity? If the problem does not come back with the cover off, I would suspect that the cover is applying mechanical stress that is related to the cause.
Love the MAC-4100, hope you get yours back in the pink soon!

 

[firealley]

Yes, I left the cover off and gently taped a few which didn't reproduce the problem. I left the cover off and it's been playing now for at least 4 hours without a problem. I'm suspecting that its the brown plug at the bottom of the photo with two wires (purple and white) which lead into a connection marked (IF OUT)....... Maybe it was just loose?