I just replaced the 2000uf capacitor near the power supply.  I am going to try to replace the 1000uf capacitor near the speakers next.  Thanks

You can hear the guitar along with the hum.  I'll check the speaker cone and voltage tonight and get back to you. Thanks

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.  I have attached a schematic of the U150RX which is close enough to my U150R model.

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

Alright I am trying to build this realllllly simple amp for a school project and I was wondering if anyone knows how I can install a headphone jack so when you plug in the headphones the speaker doesnt play? 
http://makezine.com/images/09/CrackerboxAmp_Schem.pdf

I have no real experience with electronics so please simple..

Thanks