Reverb noise issues silverface Vibrolux

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Reverb noise issues silverface Vibrolux

Postby Arvidsson on Sat Sep 03, 2016 5:23 pm

Hi! Need some input on som issues im having with a newly aquired amp. Its a early 70s vibrolux that sounds very good but has a low hum at idle that doesnt increase with volume BUT gets much worse the higher you run the reverb. Tried a bunch of things, cleaned rca jacks and installed new quailty braided cables, pulled the tank and ran it outside the cab, swapped around tubes Both driver tube and recovery, checked bias within spec, replaced cathod bypass caps. The hum is still there! Pulling PI tube kills it, checked the filter caps looks fresh definitley serviced at some point.

Any more suggestions here! :)

/Arvidsson
Arvidsson
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Re: Reverb noise issues silverface Vibrolux

Postby Dean Jr. on Sat Sep 03, 2016 7:38 pm

You say you 'swapped around tubes'. did you pull V3 to see if the hum stopped with the removal of that tube? V4? Pulling tubes one at a time can lead you to the problem area...even if the tube is not the problem. It seems likely that your problem is in the circuit....resistor, cap, reverb driver transformer...
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Re: Reverb noise issues silverface Vibrolux

Postby Arvidsson on Sat Sep 03, 2016 7:57 pm

Hi! Yes i've pulled all tubes one by one.. Only tube it went quiet with was the PI which would suggest something in the preamp but where to start :lol:

/A
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Re: Reverb noise issues silverface Vibrolux

Postby Dean Jr. on Sat Sep 03, 2016 8:07 pm

What happens when you pull V4 and rotate the reverb level pot?
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Re: Reverb noise issues silverface Vibrolux

Postby Arvidsson on Sun Sep 04, 2016 6:15 am

Dean Jr. wrote:What happens when you pull V4 and rotate the reverb level pot?


The "base hum" is still there but it doesnt get worse when you turn the pot.
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