Maybe you've just become a more demanding discerning 'audiophile' during the time you haven't used it. It happened to me 
Iv known caps to cause issues even without any visual signs.
For example, my Dad took his Hi-Fi Amp for repairs (volume control and 1 channel was distorting), dispite using what the ill minded "Doomy" would call 'Mil-spec' caps, they didn't look to be at fault.
Replacing them anyway seemes to have fixed the issue so maybe its the same case with your 1200?
It`s definately the caps Karlos. My A4000 been doin it for years.
Speaking of which, I think my 1200T and 400D could do with a new set of higher quality non-leakable caps to be replaced to be on the safe side.
