Vox Ac30 Fuse problem or bigger? (Couldn't post in AMPS)

[albano1973]

Couldn't get in AMP forum, so I'm posting here

 

First off, love my Vox Ac30CC2X, love how it sounds, gig out with it all the time. The forum page on the Vox is down, so I thought I'd hit you guys up...

 

No sound is coming out when I turn the amp on, both the red power light and the green standby light come on, but none of the tubes are cooking, only the rectifier tube slightly get red but hardly.

 

Do I need a new T500 fuse or do you think this is a bigger issue. I had to order a new T500 fuse as nobody sold them around here, but I'm worried it might be a bigger problem and that I might have to cancel shows until it's resolved. Would love any discussion on this while I wait for the fuse. If it's more than the fuse, will totally take it in to get fix and be back on the road in one or two week. Again, love my Vox AC30

[albano1973]

also does the vox ac30 have two fuses? or are there more fuses in there? I thought I read once that there was four, but I only saw two near the power and standby switch

[isaac42]

I'm not familiar with the circuitry in your amp. I'm used to amps that have one fuse: if it blows, all the lights go out.

[isaac42]

I found an AC30C2 schematic. Looks as though it has 4 fuses. So yes, your problem could be just a blown fuse. Keep in mind that there are possibly dangerous voltages present inside a tube amp even with the amp turned off and unplugged from the wall, and that fuses don't blow for no reason at all. Sometimes it's just an old or defective fuse, which is why replacing a fuse is worth a try. If the fuse blows again, then there is likely something more serious wrong with it, and you'll need a technician to look at it.

 

Looking at the diagram, it's not FS4. That's the mains fuse, and if it were burnt, you'd get nothing. FS1 is for the standby circuit. Assuming that you've checked both of those and that they're good, next are FS2 and FS3, which must be inside the amp. FS2 looks to be an odd size, 6.3A. It supplies the heaters of the power tubes, so if it's blown, you'll see pretty much what you're seeing: the power tubes won't light up, and you'll get no sound. FS3 is for the rectifier tube heater. If it was blown, the GZ34 rectifier tube would not light up, but the power tubes would, though you'd still get no sound.

 

My first guess would be FS2 is blown. Check it. If it's blown, replace it. If it blows again, I'd suspect a bad power tube. In fact, I'm leaning that way already, because, as noted above, fuses don't blow for no reason. But hey, you could get lucky. It could also be a stray wire causing a short circuit. I had a similar problem with one of my amps recently.

 

General information: never replace a fuse with a larger A value (A stands for amperes, which is current). IOW, don't replace a 3A fuse with a 5A fuse. Don't ever replace a fuse with anything else. A guy destroyed one of my amps once by wrapping a blown fuse with the foil from a chewing gum wrapper. Potentiometer shafts are often just the right diameter to stick in a fuse holder, once they're cut to the right length. Do not do this.

[WRGKMC]

Fuses don't blow for no reason. If this is a tube amp you can try the fuses accessible from the back of the head.

Use the exact same fuses only. If the fuses pop, you have bigger issues and need an amp tech to diagnose the problem.

I know the old AC30's had major issues and you need a good tech to solve them I'm not sure if the kinks in the old ones

were rectified in the newer amps But the old ones were a major challenge even for highly experienced techs.