vintage 70's technics

Hi all, my Technics SA-600 Receiver has a quiet left channel. To my ear it sounds as though it is missing much if not all of the high frequencies. I have to crank the balance right over to centre the sound at low volumes. At moderate volume it isn't as noticeable. Voltage bias is balanced okay...

I have a Technics M33 cassette deck, and the keys are sticking. To tell the truth, I'd rather pay someone who really knows how to clean, lubricate, inspect and maintain a deck, but do you have any tips on getting these function keys to loosen up? It looks like I'm going to have to pull the deck...