Vox AC30 question (no power)

Voodoomailman · 6th January 2012

Hello... I have a 1997 Vox AC30/6 TB with bluebacks and upgraded Mercury Magnetics transformers. I haven't had the amp very long and today I turned it on and after about a minute it lost power. I tried a different power cord so that's not the issue... and it's not the outlet or anything super obvious like that. Could someone please take a moment to help tell a clueless musician what to do in this situation? I'm hoping it's something relatively simple like a blown fuse or something... but I've never taken apart an amp before and don't even know where to start.

ANY advice would be majorly appreciated!!!!

Thanks in advance!!!

drbob1 · 6th January 2012

First, yes, there is a fuse in there try changing that. If it blows again immediately then something more serious is wrong. If you feel up to it, change the tubes. If that still doesn't do it, take it to a tech...

Ngr · 6th January 2012

of course check fuse first. if blown relace with a proper value one. if it blows again you have a problem with a tube.
in that case just try to remove them one at a time and substitute with a known working one: shut off the amp, replace one tube and switch it on. if it still blows fuse, repeat the procedure until you find the tube that causes the fuse to blow. if it is a pre amp or rectifier tube change it and you are done. if it is a power tube change them all!
with an ac30 it's easy to change power tubes since it is cathode biased and do not need any bias adjustment.

79_Limited · 7th January 2012

Try the fuses first. If that does not work try swapping out the rectifier tube. It is fairly common for those to go out and cause issues with power loss.

drbob1 · 8th January 2012

It's not a slam dunk that it's a tube. It certainly can be, but a bad cap, arcing in a tube socket, shorted transformer, shorted wiring in the power section anywhere... I once had an amp that started blowing fuses because someone had broken off the tip of a 1/4" jack in it, and it managed to weld itself between the B+ and the chassis. Simple fix once the top was off but, as I said before, if it still blows the fuse with no tubes in it, there are other things you need to check.

soundsundergroun · 9th January 2012

AC30's blow rectifier tubes. If you put another fuse in and it pops, change out the rectifier tube. Usually a GZ34 I think

Voodoomailman · 12th January 2012

Yep... changed the rectifier tube and it works fine now... thanks so much everyone!!!

79_Limited · 14th January 2012

Glad it worked out. I usually keep a spare rectifier tube around.

6th January 2012	#1
Voodoomailman Gear interested Joined: Jan 2012 Posts: 9 Thread Starter	Vox AC30 question (no power) Hello... I have a 1997 Vox AC30/6 TB with bluebacks and upgraded Mercury Magnetics transformers. I haven't had the amp very long and today I turned it on and after about a minute it lost power. I tried a different power cord so that's not the issue... and it's not the outlet or anything super obvious like that. Could someone please take a moment to help tell a clueless musician what to do in this situation? I'm hoping it's something relatively simple like a blown fuse or something... but I've never taken apart an amp before and don't even know where to start. ANY advice would be majorly appreciated!!!! Thanks in advance!!!

6th January 2012	#3
Ngr Gear maniac Joined: Nov 2008 Location: Roma, Italia Posts: 250	of course check fuse first. if blown relace with a proper value one. if it blows again you have a problem with a tube. in that case just try to remove them one at a time and substitute with a known working one: shut off the amp, replace one tube and switch it on. if it still blows fuse, repeat the procedure until you find the tube that causes the fuse to blow. if it is a pre amp or rectifier tube change it and you are done. if it is a power tube change them all! with an ac30 it's easy to change power tubes since it is cathode biased and do not need any bias adjustment. __________________ Francesco ngrstudio@fastwebnet.it

9th January 2012	#6
soundsundergroun Lives for gear Joined: Jun 2008 Location: Ohio Posts: 729	AC30's blow rectifier tubes. If you put another fuse in and it pops, change out the rectifier tube. Usually a GZ34 I think __________________ http://myspace.com/soundsundergroundstudio

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6th January 2012	#2
drbob1 Lives for gear Joined: Nov 2009 Posts: 1,420 3 Reviews written	First, yes, there is a fuse in there try changing that. If it blows again immediately then something more serious is wrong. If you feel up to it, change the tubes. If that still doesn't do it, take it to a tech...

7th January 2012	#4
79_Limited Lives for gear Joined: Oct 2006 Location: Atlanta, GA Posts: 528	Try the fuses first. If that does not work try swapping out the rectifier tube. It is fairly common for those to go out and cause issues with power loss.

8th January 2012	#5
drbob1 Lives for gear Joined: Nov 2009 Posts: 1,420 3 Reviews written	It's not a slam dunk that it's a tube. It certainly can be, but a bad cap, arcing in a tube socket, shorted transformer, shorted wiring in the power section anywhere... I once had an amp that started blowing fuses because someone had broken off the tip of a 1/4" jack in it, and it managed to weld itself between the B+ and the chassis. Simple fix once the top was off but, as I said before, if it still blows the fuse with no tubes in it, there are other things you need to check.

12th January 2012	#7
Voodoomailman Gear interested Joined: Jan 2012 Posts: 9 Thread Starter	Yep... changed the rectifier tube and it works fine now... thanks so much everyone!!!

14th January 2012	#8
79_Limited Lives for gear Joined: Oct 2006 Location: Atlanta, GA Posts: 528	Glad it worked out. I usually keep a spare rectifier tube around.