Need help from amp guys. AC30 problem

  • Thread starter Thread starter Enjolras56
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Enjolras56

Enjolras56

New member
Hey guys-

Just turned on my Vox AC30cc2x for the first time in about 6 months.
It's sat mostly unplayed for the last 3 years in my garage as it does not tonally work for my current band situation. FYI- we recently moved and the amp was transported on a hired moving truck.

So I plug in my in-tune Les Paul at a low volume. I hit an open E chord and it sounds like I'm going through a ring modulator. Especially on low notes on the 6th string it just sounds out of tune, farty, and incoherent if that makes sense.

I turned it up a little which improved things a bit, but I notices it breaking up sooner than I would expect.

Wanted to see what potential problems you guys think I might be facing. From some quick Google-IMF of my symptoms, it seems it might have a filter or power cap issue? (which I know nothing about)
Any ballpark ideas on what kind of cost to expect.
One of the pains of tube amp ownership is the cost involved in maintenance, especially having multiple amps!
 
Check for tube micro-phonics with a non conductive object like a chop stick or pen. Tap the tube with the amp on and if its makes noise there is your problem.

Could also be your reverb tank, pull the reverb tube driver and see if that helps. V4

VoxAC15-30Layout2007-08-17b.gif
 
Just a heads up, that diagram is something other than the CC series ac30, which only has 3 preamp tubes. :)

Have you tried new tubes? That's always the first thing to check, and it's an easy thing to do on AC30s because as long as you use a matched quad of power tubes, you don't need to take it to a tech for biasing.

Based on the ring mod sounding description, I'd start by changing out the power tubes. But if you've got a tube amp, it's worth having spares of everything - you'll need them at some point, and it'll keep you from having to call a tech unnecessaraly.

Something else worth mentioning... if you use the standby switch, stop! :yes: It's badly implemented on the CC series. The amp doesn't need it and it actually can damage the amp over time. Just leave it in the on position all the time and pretend it doesn't exist. If you don't believe me, and it's fair if you don't, google it. :)
 
Cirrus":26nipilg said:
Just a heads up, that diagram is something other than the CC series ac30, which only has 3 preamp tubes. :)

Have you tried new tubes? That's always the first thing to check, and it's an easy thing to do on AC30s because as long as you use a matched quad of power tubes, you don't need to take it to a tech for biasing.

Based on the ring mod sounding description, I'd start by changing out the power tubes. But if you've got a tube amp, it's worth having spares of everything - you'll need them at some point, and it'll keep you from having to call a tech unnecessaraly.

Something else worth mentioning... if you use the standby switch, stop! :yes: It's badly implemented on the CC series. The amp doesn't need it and it actually can damage the amp over time. Just leave it in the on position all the time and pretend it doesn't exist. If you don't believe me, and it's fair if you don't, google it. :)
Click to expand...

I am not versed the the CC series and thank you for the correction. However why would you start replacing tubes without knowing if its the cause of the problem?

Also what you said about not using the stand by switch? Could you elaborate more on this? Its my understanding when you switch the amplifier on with stand by engaged the only electricity flowing thru the amplifier is the DC heaters on the tubes. When you take it off stand by then the circuit is active.

I will try to dig up a schematic of the CC series see what I can find out out what you mean by badly implemented.

BTW I am not doing this to prove you wrong. I wan't you to be correct. I just wan't to know exactly how what your saying works. No hard Feelings.

Luke
 

I am not versed the the CC series and thank you for the correction. However why would you start replacing tubes without knowing if its the cause of the problem?

Also what you said about not using the stand by switch? Could you elaborate more on this? Its my understanding when you switch the amplifier on with stand by engaged the only electricity flowing thru the amplifier is the DC heaters on the tubes. When you take it off stand by then the circuit is active.
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LukeCurd":3n3eejcw said:
My quick solution without rewiring anything is just to pop in a yellow jacket ysr. Its a solid state replacement that plugs into your rectifier tube socket.
http://www.yellowjacketstc.com/Product_Manuals/YJR.pdf
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https://www.premierguitar.com/Magazine/I ... erter.aspx
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Hey Luke no probs at all :)

I was suggesting starting out by replacing the tubes because it's worth having spares anyway. So best case is that they solve the problem, and save Enjolras56 from having to pay an amp tech to do it, and worst case is they don't solve the problem, but now at least he's got spare tubes for when they eventually do need changing.

Also, I had a similar "ring mod" type sound to my amp that started happening halfway through a gig, and it turned out to be a power tube that had gone bad. I guess there's quite a few things that'd cause that kind of problem, even a healthy AC30 usually has some undertone caused by the filtering not being perfect so it might well be a filter cap issue. I just figured it's worth trying tubes first since it might be them and this is the easiest way to find out. :D

I used a weber copper cap for a while which I think is the same sort of thing as the yellow jacket, that's a really good idea! In the end since I was modding the amp anyway I just disconnected the standby switch.
 
Thanks for sharing your knowledge guys! Btw, glad to hear it won't need re-basing if I used a matched quad.
I recently learned my lesson that jarring car rides can really do harm to your power tubes, so I suspect the moving truck may have done it? Who knows...
Do I have to be careful about voltages with unplugging/plugging power tubes?
 
Enjolras56":15zk6kz7 said:
Do I have to be careful about voltages with unplugging/plugging power tubes?
Click to expand...

Tubes are safe to handle. The don't carry any electrical charge like a capacitor does. They can heat up to 200 degrees centigrade so just make sure they are cool before you pull em. Other wise swapping tubes is a pretty easy task. Don't force the tubes, the holes line up with a divider and only go in or out one way. Gently rock them back and forth while pulling up.
 
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