Vox T60 60watt amp

mitchelr · 1st January 2009, 04:19 PM

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 · 1st January 2009, 04:46 PM

I don't think the schematic got there

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

mjf · 1st January 2009, 08:06 PM

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

mitchelr · 2nd January 2009, 03:33 AM

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 · 2nd January 2009, 10:46 AM

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 · 2nd January 2009, 05:23 PM

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

1st January 2009, 04:19 PM	#1
mitchelr diyAudio Member Join Date: Nov 2008	Vox T60 60watt amp 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

1st January 2009, 08:06 PM	#3
mjf diyAudio Member Join Date: Jan 2009 Location: upper austria/near linz	humming hallo! does the amp work well and is he only humming?or is he generally bad? k. regards..........

2nd January 2009, 10:46 AM	#5
mjf diyAudio Member Join Date: Jan 2009 Location: upper austria/near linz	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..............

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1st January 2009, 04:46 PM	#2
mitchelr diyAudio Member Join Date: Nov 2008	I don't think the schematic got there one here :- http://myweb.tiscali.co.uk/ronniereplay/t60

2nd January 2009, 03:33 AM	#4
mitchelr diyAudio Member Join Date: Nov 2008	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

2nd January 2009, 05:23 PM	#6
basreflex diyAudio Member Join Date: Oct 2007	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

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