AC30CC Help/ Troubleshooting

[jdean492]

Hello all, can anyone help me?

I recently purchased a Vox AC30CC used from someone local. I plugged in before I bought it and everything sounded great. But here I am three days later and the amp has stopped making any noise what so ever. I am hoping that it is just the power tubes that need to be replaced, but I would like some confirmation from some other people.

Here are the symptoms of the amp:
- was working fine until I moved it from my house to our band's practice space. It wasn't dropped or anything, no hitting big bumps in the car.
- the power and standby lights come on.
- replaced the guitar cable I was running through, no sound.
- plugged into a different speaker cabinet, no sound
- I took the chassis out and pulled the power tubes and put them back in, still no sound
- the fuse still looks good
- when the amp is powered up, the rectifier tube glows but not the power tubes.

Any ideas?

Thanks

 

[Wagster]

Sounds like the rectifier blew. Buy a JJ or NOS 5AR4 and change the fuse by the power cord. The stock Sovtek 5AR4's are notorious for failing. Also check and make sure all the preamp tubes are lighting up. I've had several Tong-Sols 12AX7's die on me.

 

[sixstring531]

Rectifier blew, change fuse under cable (one is blown if not that one). I prefer the sovteks as every JJ (and I had an ac30) rec I've owned has blown, some within the first year.

 

[jdean492]

You guys sure about the rectifier tube? Its the one glowing. Not the power tubes

 

[54GT]

Had something similar happen when I first got mine. As folks above suggest, replace rectifier tube; also there are three (?) fuses in there in different locations if I remember right. (see if you can download a schematic). Need to make sure all are good, and I recall at least one being pretty well hidden on the circuit board.

 

[Steve73]

Yeah, this exact thing happened on my AC30cch. First, try and change the rectifier as mentioned. If that doesn't work, it is probably the heater fuse, which is a bit of a PITA to get at. You can't see it from the back of the amp. You first have to pull the chassis from the cabinet. Then you have to take off the slider board on the bottom of the amp. I think the fuse is labelled F2. Careful in there, there are potentially lethal voltages present. Good idea to discharge the caps before digging around in there. After you get it replaced, one of the most common things guys say to do to avoid this is to not use the standby on the amps. Just leave it off all the time and power the amp up without it. Another solution is to get a Weber Copper top to replace the rectifier tube.

This might be of use to you:
www.voxamps.com/downloads/PDF/AC30_troubleshoot.pdf

 

[jdean492]

OK, I am going to do as suggested here and replace the rectifier tube along with the fuses in all locations, but can someone please explain to me why the rectifier tube would still be glowing if it is the one that needs replacing? I feel like I have a decent understanding of amps and electronics in general so feel free to get as technical as you like. I would just like to learn the reasoning behind this diagnosis.

I will update when I try out the new tube and fuses.

Thanks guys

 

[utterhack]

btw, leave the standby switch set to "on/standby" at all times, or this will happen again.