Amp problems

dainbramage

dainbramage

New member
My AC30C2x is really messed up. I turn it on and the volume is really low and muddy, and there are these crackling sounds coming out of it that is much louder than the guitar. Sounds like breaking ice, you know like cracking glaciers that you might have seen on television. I figured it was the tubes, so after having spent most of my money on my new guitar I was desperate enough to spend the rest of it on a full set of tubes. Swapped them all today and expected everything to be fine, but no, it sounds just the same.. :facepalm:

Now I don't have any money left to leave it at a tech. A LITTLE bit frustrated over here. New guitar and everything. Excuse my swedish, but FUCK.
 
arcaxis said:
My first thought was a loose or dirty tube socket contact, but having swapped out the tubes that may have "fixed" that sort of thing.
Click to expand...

Hey arcaxis, thank you so much, I cleaned the tube sockets with electronic cleaner and whaddayaknow, the noise is almost gone (it spits a little sometimes but not nearly as much) and the sound doesn't sound muffled anymore. Awesome! However the volume is really really low, I can turn the preamp volume to max and hardly get any saturation. It is supposed to distort like crazy and be deafening. I don't think it would even be able to play over a drummer with everything set to max as it is now. It also hums quite a bit which it probably would anyway with volume set that high. Can I damage the amp playing like that you think?

One of the preamp-tubes I got at the store was a 12AY7/6072A instead of the recommended 12AU7WA. The guy said I could use it if I used the 12AU7WA tubes in socket 1 and 2. He said I would get a "different sound" but that it would work. Do you think that has got anything to do with the drastic volume change. It most certainly seem to be preamp-related since it does not distort at max volume.
 
That is indeed my amp.

Thanks a lot arcaxis. Great advice. It is getting late around here and people are sleeping in this house but I will look more into it after work tomorrow, call the store and also see if maybe the old tubes still work in case the problem was dirty sockets. It does still crackle a bit sometimes but definitely less than it did before cleaning the sockets. Bypassing the effect loop did not have any effect. Will also try bridging the send and return.
 
Try moving each of the tubes and see if you can recreate the noise. I once had a bad tube socket that did something similar to your description. You can "sometimes" retension the socket to hold the tube firmly.

If this does not recreate the problem you could have a bad solder joint
 
Sounds to me like what I just had on one of my amps....mainly loose tube sockets, and maybe a bit of oxidation.
The "springs" that hold/contact the pins can open up over time, and you get all that noise. If you *gently* rock the tubes with the amp on, and you hear lots of noises...that's the problem.
Cleaning with DeOxit stuff is step one, I like to use the Caig D100L, and just tab it on the tub pins with a Q-Tip, not real wet, just enough to leave a film, then work the tubes in/out of the socket a couple of times and then seat the tube all the way normally. The D100L cleans, but also helps with improving the connectivity....
....but you really need to re-tighten the springs to get all the noise out.

This guy shows it nicely how it's done. Not a hard thing to do....mind the instructions on draining the amp juice off before you start sticking things into the sockets, and if you use a screwdriver with an insulated handle, all the better...and of course, before starting, the AC plug. :)
I wouldn't bother with re-soldering the pin connections unless after tightening, you can still gently rock the tube and get lots of noise and movement of the entire pins. On fairly new amps, the solder joints should be fine, it's mostly the pin springs that open up.
In my case, I always find this type of problem with the preamp/9-pin sockets. I've never had issues with the bigger power/rect tube sockets.
Also, you can stretch the springs inside the tube covers out a little more so that they push down on the tubes a bit harder, which will keep them more solid in the socket. Watch it, if you pull hard enough, the springs can come out of the sleeves...but no big deal, just push them back in. You don't need to stretch them a lot...just make them maybe a half to one centimeter longer than they were.

Billm Audio » Re-tension, re-solder your tube sockets
 
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The amp has been off and unplugged for about 24 hours now, but I am still a little sceptical. How can I be sure there is no charge left? How much of a shock could it give? (i.e. is it potentially lethal?). I have pretty much no experience with electronics.
 
dainbramage said:
The amp has been off and unplugged for about 24 hours now, but I am still a little sceptical. How can I be sure there is no charge left? How much of a shock could it give? (i.e. is it potentially lethal?). I have pretty much no experience with electronics.
Click to expand...

Google search how to discharge your amp. Just leaving it off and unplugged isn't always enough. One common way is to turn it on, standby off, like you're playing, hit a chord, then power it off without flipping standby. That can do it, but the foolproof way is to ground one of the preamp pins to the chassis ground with a jumper wire, and then check the caps with a voltmeter, but I can't remember which pin it is. Google it. You'll see a little tiny spark, but it's okay. You might need to do it a few times because capacitors can "rebuild" a charge. They're like batteries. I'm no amp tech by any means, but I've done the pin ground thing and it works perfectly. When the caps show no charge you can dig around and not die.
 
dainbramage said:
How much of a shock could it give? (i.e. is it potentially lethal?).
Click to expand...

Oh yeah....it can give you a nice jolt, or even knock you on your ass...and it can be lethal.

I zapped myself twice last weekend chasing some tube noise, and having the amp out of the combo....so of course, the guts are open.
Now I know my way around and what not to touch, etc....I've tinkered inside of amps enough times...but in the heat of the moment as I was moving the chassis around, I managed to touch a hot wire, and OUCH!...then I did it again 2 minutes later.....OUCH!

:eek:
:facepalm:
 
Greg_L said:
....but I've done the pin ground thing and it works perfectly....
Click to expand...

Yeah, that's the smart thing to always do, or at least check if there's any voltage left in the caps with a meter, since some amp circuits include a bleed resistor in the circuit for the specific purpose of draining off the caps, so you can check to see when it's drained off.
You can also drain the caps by going right off the positive cap leg to chassis ground with a screwdriver....just watch you don't touch the metal of the screwdriver.

Here's three ways to do it. I've been meaning to make one of the bleed resistor hook-ups for awhile now....just haven't gotten around to it, but after getting zapped last week, I think I'll make one up to have. :D

Discharging Filter Capacitors
 
had dirty pin receptacles in my Classic thirty. The 4 el34s are in series, one goes out they all go out. Got in there and cleaned out the sockets and voila, the problem was gone.
 
I pulled the amp apart and found what I thought was a bad solder joint on one of the heater pins. I resoldered that and figured I was out of the woods. Brought it to practice and within fifteen minutes she conked out. Brought her home and took it apart again, couldn't find anything wrong. Decided to clean all the tube sockets and tube pins, put her back together and she hasn't gone dead since?
 
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