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Vox AC50 head wrecking problem!!:-(
Old 29th December 2010
Gear Nut

Vox AC50 head wrecking problem!!:-(

Hey everyone,

I know its a bit off track but im wondering if ye could help me with a problem im having with my vox ac50 i cant get my head around..

I have been given an very old ac50 which isnt working.. When i plug in a guitar all i get through the cab is a harsh distortion noise when i play hard. If i play light nothing comes through. When i turn up the volume however when playing light i seem to get the same noise as when i play hard. It happens on both channels (normal and bril). Iv tried different cabs but to no avail.

Would anyone have any ideas what might be wrong? Iv checked all the soldering and everything seems to be ok but id be a fairly new at the DIY game!!!;-)

I followed the schematic and see that the R29 which seems to be a 750r 3w resistor seems to be bloted out. Im thinking it might be blown. Would this cause the sound im getting?

Thanks a million

I can post sound samples and pics if need? Any help or advice ye could give me would be great..


Old 29th December 2010
Gear Nut

How old are we talking? 60s? Wish I could help...could be a tube problem. I say take it to a tech. Probably your best bet, but maybe someone more knowledgeable than myself can chime in.
Old 30th December 2010
Gear Nut

Ya its from late 60's.. Cheers for the reply.. I replaced the tubes twice thinking it was them but to no avail.
Old 30th December 2010
Gear Nut

Oh I also just today replaced R29 (the 750r 3w resistor) and the minute i turned on the amp it just burned out straight away..

Would anyone have any ideas?

Thanks a million
Old 30th December 2010
Lives for gear
Colonel Blues's Avatar
Go straight to a tech before loosing everything !!!
Old 30th December 2010
Lives for gear
I think that's a screen resistor, very necessary for the operation of the amp and if it's blowing then there's plate volts (450) somewhere there shouldn't be. Unplug it. Take it to the nearest tech. That's way too cool an amp to destroy learning "fixit" on, and it's real close to blowing up kind of problems...
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