Maine 120C Amp: How to open up the front. Crackling pots, 2nd channel not working

[the_chemist]

Dear all,

I am a newbie to this forum.

I have a Maine 120C Amp, same as this one:
https://reverb.com/item/6780006-main...age-combo-1979

I haven't used the amp for quite some time (3 years?). It used to work okay (some humming).
It turns on okay, but makes now more humming and crackling noises.

The left channel still seems to work: When I turn the volume pot, it makes really LOUD crackling sounds, but I can plug in my guitar and it works.

I found some advice about putting lubricant into the pots. However, I cannot reach them. The front can be unscrewed, but cannot be removed as the inner part is too bulky to pull out... Not possible to remove it from the back, either.

Does anybody have some experience with removing the front and servicing pots on this amp?

Thanks!

Best
the_chemist

[the_chemist]

I solved the issue with removing the front. The trick is to remove the speaker cover first, then there is enough space to pull out the front.
I have lubricated the pots of the left channel and now the left channel works much better, less crackling when turning pots.

I still have a second issue: the right channel (the main one: with reverb, colour, etc.) is not working. The pots do not crackle when turned or touched.

From the circuit layout that is visible to me when opening up the front, it looks like only one signal (left and right channel combined) goes to the back and there to the speakers (but I could be wrong). Therefore, I think it either a problem with the pots or the circuit board for the right channel.

Any suggestions how to tackle this? There have been requests for the circuit layout for the Maine 120C amp on this forum, but so far none were posted publicly. Does anybody have a layout for this amp?

{EDIT: The pots of the right channel do crackle when turned. Also, when reverb pot is set to about 1/3 and the amp is slightly touched, a reverb signal is produced. This indicates that this channel still produces some signal for the speakers. Maybe the plug-ins are defective? Any thoughts?}

Any help or suggestions are highly appreciated! Thanks

Best,
the_chemist