I suspect your electrolytic capacitors have gone bad, they might have leaked as well, so look closely for damaged traces or components on the board.
Its not an A1200.
@OP, what model is it, standard A500 or an A500+. As plus has battery that trashing everything.
Best next action to re-seat all chips. Carefully lift them and push them back into place.
Despite what people say, 99% of A500 issues are caused by connection issues on chips.