Vox AD30VT problems

RobK

I'm having a bit of a problem with my AD30VT. It's one of those really annoying random and intermittent things, so I'll try my best to explain what's happening.

Basically the amp cuts out. Just no sound.

Last week it started cutting out while I was playing. The sound would just be gone. Then it would either suddenly come back with a hard strum or it would slowly "crackle" back to life. Other times it would sound like the volume was being turned up slowly and it would come back that way. It would also, on occasion, not come back fully - just sound sortof really distorted and quiet (even on a clean channel). Sometimes it wouldn't come back at all, until I switch it off and do a reset. Then it'd be OK for a few minutes and start doing the same thing again.

This whole wekend I had no problem at all.

Today, I switched it on and no sound. Plugged my headphones into the line/phone socket and it works fine. Unplugged the headphones and it, again, crackled back to life. Messed around just strumming and picking strings and could hear it crackle again.

I have tried swapping cables and guitars and I get the same. Incidentally, the cables and guitars work OK plugged into my PC so I don't have a reason to suspect them.

So, any ideas anyone? Feel free to ask for more info and I'll provide what I can. What could it be - tube? electronics? speaker?
(I did notice a small hole at the edge of the speaker - right at the edge - the doped part, right next to the baffle - don't know whether that would cause any of this though)

Just want to get an idea of whether this is just something I could sort out by replacing a part or whether I should just take it to someone to look at.

Thanks for the help/ideas.

EDIT: Here's a link to a sound file - just stuck a mic in front of the amp - not beautiful, but it gives an idea of the crackling I'm talking about ?

http://www.box.net/shared/gqjymaz80q

AlanRatcliffe

Today, I switched it on and no sound. Plugged my headphones into the line/phone socket and it works fine. Unplugged the headphones and it, again, crackled back to life. Messed around just strumming and picking strings and could hear it crackle again.

Dirt in the phone socket is a possibility. Try inserting and removing a jack a few times, spray with switch cleaner if you have. Otherwise the connection to the speaker is another possibility - check any plugs/sockets/joints.

Danny-B

Sounds kinda like a capacitor. Had the same issue with my JC and thats what they claimed was causing it.

RobK

Alan Ratcliffe wrote:
Today, I switched it on and no sound. Plugged my headphones into the line/phone socket and it works fine. Unplugged the headphones and it, again, crackled back to life. Messed around just strumming and picking strings and could hear it crackle again.
Dirt in the phone socket is a possibility. Try inserting and removing a jack a few times, spray with switch cleaner if you have. Otherwise the connection to the speaker is another possibility - check any plugs/sockets/joints.

I'll have to get some spray tomorrow and try. Just plugging and unplugging doesn't help. Shone a torch into the input socket - looks spotless though.

Danny B wrote: Sounds kinda like a capacitor. Had the same issue with my JC and thats what they claimed was causing it.

TomCat

I recently had a strange distortion on our Vox Pathfinder 15. turned out to be the loudspeaker spade terminals being loose on the loudspeaker terminals. This also being a Vox amp could be suffering from the same problem.

Try removing the spade terminals off the loudspeaker terminals and pinch the terminals lightly with a pair of pliers. Push the terminals back onto the loudspeaker terminals. They should push on tight.

Once we did this to our amplifier the tone and overall sound of the amplifier improved greatly.

Danny-B

Danny B wrote: Sounds kinda like a capacitor. Had the same issue with my JC and thats what they claimed was causing it.

That I wouldn't be able to see. I can take a look inside the chassis for any loose connections, but if it's one of the components, I think I'll leave it to professionals. With my luck I'd most probably end up electrocuting myself. ?
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Best to leave it to the professionals then, I would never try opening my amp, too scared ?

RobK

TomCat wrote: I recently had a strange distortion on our Vox Pathfinder 15. turned out to be the loudspeaker terminals being loose on the loudspeaker terminals. This also being a Vox amp could be suffering from the same problem.

Try removing the spade terminals off the loudspeaker terminals and pinch the terminals lightly with a pair of pliers. Push the terminals back onto the loudspeaker terminals. They should push on tight.

Once we did this to our amplifier the tone and overall sound of the amplifier improved greatly.

OK, did that and in the last 10 minutes or so no crackle. The lugs on the speaker were a little loose, you could wiggle them, but they wouldn't just pull off easily - seemed to have decent contact. I pinched them a little tighter - to the point I had to use pliers to push them back on, so they're quite tight now.

I'm hoping this does the trick, but it might just be that the amp is just in one of it's happy places and behaving again ? . I'm holding thumbs, though. Thanks for the suggestion.

TomCat

If the wire were wiggling...then they were too loose. They need to be tight.

Keep us posted if the problem has gone away....

RobK

I always thought they needed to be just tight enough to make contact and not pull off if tugged a little. They wiggled side to side, but stayed on when tugged, so I thought they were OK.

Going to leave it for a bit and try it a little later (though quieter - playing isn't good enough for neighbors to bear for even short bursts ? ), and tomorrow.

Thanks again everyone.

RobK

So, two days later and I haven't heard any crackling from the amp/speaker. Also seems to be less "noise" when it's just standing idle.

Seems like it was :

- as Alan said - one of the joints (thought I never thought it would be the speaker ones)
- as Tom said - the speaker lugs/terminals

Still holding thumbs, as it did come right before, but then went wonky again. Today I'll close the back up again and if it still works after this weekend, I'll consider it case closed ?

Thanks for the help again.

EDIT: Looks like I spoke to soon. Had the amp on, doing nothing and the crackle re-appeared. Only thing different from yesterday is that I put the back on. Going to buy some of the electronics cleaner spray and spray the whole thing. If it still does it, it's off to amp hospital for, hopefully not too much, surgery.

RobK

So, sprayed everything with the cleaner spray. Not much gunk came out. Waited for an hour before I put everything together.

Results:

The attenuator knob at the back generated the crackling when turned. Knob is new suspect.

No crackling through line out since the line out bypasses the tube (?) and the attenuator, I think (attenuator knob has no effect on the line out).

Could the tube be a problem?

Did some more spraying/cleaning. Lots of cleaner on the attenuator. Pulled the tube as well and sprayed cleaner into the socket. Put everything back together.

Turned the attenuator knob backwards and forwards a bit - slight crackle which went away. Turned everything to max and nearly had a heart attack and crapped my pants at the same time. The dogs across the street started howling in pain. This thing is LOUD. I think it's louder than it was before. Actually I'm pretty sure it is.

So far, been OK for about 30 minutes. Now I wait and see.

TomCat

HaHaHaHa........ ? ? ?...I'm having a good laugh as I did the same with my friend's Hot Rod Deluxe. After reassembling the amp I plugged the loudspeaker into the wrong jack socket and ended up with a very soft sounding 40watt tube amp. After some investigation the only conclusion I coud come up with was the loudspeaker jack being in the wrong output. Replugged the loudspeaker to the other socket, switched on and played a cord and screamed at the same time.....the volume knob was still at 8 out of 12 with a nice hot humbucker plugged in.....Full drive off 40 watts of tube power in a 3m x 3m room is....LOOOUUUUUDDDDD....... ? ?. I felt like Micheal J Fox in the beginning of "Back to the Future"....... ? ? ? ?

RobK

Well, it's been 5 days and no problems. Seems the attenuator knob was the problem, although I don't doubt that taking it apart and making sure all the other connections were tight and clean helped as well.

I suppose being at the coast, it might be beneficial to do some cleaning once every 6 months or so to keep something like this from happening again.

Now that I know how loud it can be, I'm starting to think that hooking a 2 X 12 cab into it might not be such a good idea ?