NAD: Tech21 TM60, but no sound on Ch1

Hi! I picked up a TM60 over the weekend from someone a few hours away. I didn't have good chance to check it out thoroughly. Dude send me a video showing that the amp worked as he twisted some knobs and pushed some buttons and I heard sound, so i thought it was good enough to buy without further checking.

Turns out there's basically no volume on channel 1. if i hit the channel switch to ch2, the amp works fine. but when i switch back to Ch1, no sound. well, basically no sound. if i turn all 3 knobs up to 10, i hear a faint sound.

So i did my research, and figured I needed to Deoxy it from head to toe, especially the loop jacks. I took out the chassis, sprayed everything down, and did all the jacks directly and plugged it in/out many times.
I put the chassis back in, and VOILA, Ch1 works perfectly! Sounded great and I couldn't be happier.

Then i turned the amp on again today, and the same situation. ugh. pulled the chassis again, sprayed everything down again, and Ch1 came back! but then I took the cord out of the amp, plugged it into another amp to compare tone, and when i plugged it back in, Ch1 didn't have any sound.

Yes, i can pull the chassis again, or just try spraying the loop jacks again, but this doesn't sound like the typical issue. I even left the loop jacks connected by a 6" cord, but still no sound on Ch1.

Any ideas or suggestions? I don't think i'm going to be able to return it, so i want to see what y'all think the issue could be and hopefully something i can fix.
thx!

 

didn't come with a footswitch. i have a 2-button switch which i tried, and it did switch channels, but no difference in sound.
thx!

 

checked what i could. its small and tight in there didn't see anything glaring. sprayed everything down again (3rd time) and the sound has come back on channel 1. pretty buzzy, though, and with bite off, drive at noon and punch at 0. trying to get BFDR tone out of my strat at home office (ie: low) volume. level on ~3.5 and its barely above conversation level. that doesn't bother me too much, as I just noodle around in my home office. just not sure if this is typical. i'll just leave it on with guitar vol at 0 while i'm away for an hour. hopefully still good then. and the buzz is coming from the reverb. its set ~4, but that's pretty buzzy.
thx!!

 

quick update - i left it on for about 4 hours last night, not playing it really, but checking it every hour (geez, it sounds like I have a sick kid!!). worked fine and then i turned it off when i went to bed. just turned it on now and ch1 is still working!! hopefully it lasts, but wow, it must've really been badly oxidized for it to take 3 deep cleans.
And to be honest, i'm still a little concerned that it only affected ch1 and not ch2. odd..
thanks for all the help and suggestions!

 

Just an update. I've been playing the amp in my home office for the last week, and it sounds great with my strat! I even love the bridge pup now on ch2 with the knobs at mid (no weep) and treble at 4pm. sounds killer!
BUT.... the problem returned today. I hadn't touched the plug and had the same cord attached all week. when i went to change cords to a little wireless thing i have, ch1 cut out again. exact same symptom. ch1 didn't work but ch2 did. ugh.
I plugged the input into the return jack of the loop, and ch1 worked! no reverb, of course, but that makes me think that the problem is with the input jack. The channel switch button seems to work fine. not sure why the input jack would cause this problem, but not sure what else it could be.
Also, I plugged headphones in and ch1 worked fine.
So i'll pull the chasis again and spray everything down again. I hope it works again until i figure out my next steps.
But the amp does sound damn good!!