Hey Everybody

Ok I just got this old Univox solid state amp from the early 70's. Its kinda in good shape, with a spring reverb and tremolo and 2 ten inch speakers.

BUT there is a CONSTANT hum when I turn on the amp, with or without a guitar plugged in. Its quite loud. You can find a schematic here: http://www.abeltronics.co.uk/download.php?manu=univox&file=univox-150rx-amplifier-schematic.pdf
I wanted to post it but it too big....

So far I have replaced the power supply capacitor (the 2200 uf and 35V one, {the schematic says 2000uf but that wasnt what the actual part said}) and cleaned all the contacts.

Does anybody have any suggestions to what it could be? Should the amp become parts? THANKS
It'd be hard to troubleshoot it over the internet. My guess is that one of the jacks is not closing properly.

Looking at the schematic, though. Only the "guitar" input is a shorting jack.

Another guess, I'd touch the chassis. Any bare metal on the chassis. If this gets rid of the hum, switch the plug out for a 3-prong grounded plug.