Vox T60 60watt amp

[mitchelr]

Hi
I have a 1960's Vox T60 guitar amplifier, which is humming.
I have disconnected before the OC35 ( No.1 on attached sch)
and the humming stops.
If I reconnect and disconnect at C8 ( No.2 on attached sch) the
humming starts.
I have changed the OC72 with no effect.
Any idea's
Thanks for your time
Ron

 

[mitchelr]

I don't think the schematic got there

one here :- http://myweb.tiscali.co.uk/ronniereplay/t60

 

[mjf]

humming

hallo!
does the amp work well and is he only humming?or is he generally bad? k. regards..........

 

[mitchelr]

Yep The amp works well, its just that annoying hum.
I am going to order a new set of elec cap's
I hate to admit it , but it was the first amp I bought ( early 60's)
Regards
Ron

 

[mjf]

humming

there are some reasons for humming when he works:
first of all a bad ground connection,perhaps in the input connectors(clean it with kontakt-spray),or a bad cableconnection(bad soldering point,broken ground connection...).and there could be some electrolytic caps gone weak and old...............
greetings..............

 

[basreflex]

did you check the voltage at point C, (-12.5V vs gnd) the zener may be defective. you could also check the collector voltage of the OC35. if this is far off from -16.5V then the zener would be defective ..

bas reflex