Diagnose Tube Amp Problem?

[Meyatch]

Ok, so my guitarist bought new tubes for his Line 6 Somethingorother amp.

He put the new tubes in, let the amp warm up on standby, played quietly for a couple minutes, then the amp made 2 popping sounds, the second one louder than the first one, and then there was no more sound.

He says everything turns on, lights up, functions as normal, including his pedalboard (which is like a built in controller for the amp or something) it just doesn't make any sound.

He tried new cords, none of the fuses blew, and he even tried putting the old tubes back in and it still doesn't make any sound.

Firstly, is this a bias issue? He did not bias the amp, but he is using the same model of tubes that were in it before. I understand that even the exact same model of tube will bias slightly differently, but it was my understanding that it should still work, just not optimally.

If it is not a bias issue, what do you think is wrong with it?

He is trying to get ahold of someone to take a look at it, but we have a show on saturday, and I'm not sure anything will get done by then. All the effects he uses are built into the amp, so I was thinking maybe we could run the preamp out of it into another amp. But I don't want to do furthur damage to the amp either.

-mitch

[JimmyM]

did he try putting the old tubes back in?

[Meyatch]

yes, behaves the same way. Everything appears to work, but no sound.

[blendermassacre]

I would say that the line 6 tube amp guitar stuff isn't the easiest to diagnose via the internet. Too much could have gone wrong.

[Meyatch]

perhaps, but perhaps it is something that could happen to all amps. I'm just wondering if its a symptom anyone has ever encountered.

[JimmyM]

Originally Posted by Meyatch

perhaps, but perhaps it is something that could happen to all amps. I'm just wondering if its a symptom anyone has ever encountered.

when you do wholesale tube changes when everything works, yeah, stuff like this can happen. my motto has always been "if it ain't broke, don't fix it." i'll leave my tubes in my amps until something goes wrong, then i'll only replace the tube that's bad. too much can go wrong on total tube changes. doesn't help you to diagnose it, but it might prevent something like this in the future.

anyway, blender's right...in a line 6 amp, it could be almost anything.

[jelwood]

I'm kind of wondering that myself. The whole "tubes have to be replaced every year or whatnot," is a complete myth according to the general consensus among the notorious SVT users we have here. Why did he decide to change the tubes at all if the "old" ones weren't broken? Sorry, that doesn't really help. Good luck with the tech.

[T-Bird]

Hi.

The only feasible option in a case like this is a trip to a tech. The high voltage safety requirements with all tube amps is one thing, the diagnostic/safety circuits in amps like Line6 another.

Unless someone comes up with a "booting sequence" it's highly unlikely that the problem can be solved over the 'net.

The people who wonder about tube changes with guitar amps, well the guitar amplification world has absolutely nothing to do with bass amplification.
Since 8 times out of 10 the goal is to get a responsive output section distortion and there's perhaps 10 times more differently behaving tubes to choose from, guitarists roll the output tubes like (some of us anyway) we roll pre amp tubes.

Regards
Sam

[KramerBassFan]

Yep, not to mention, it likely has tiny integrated components, which can be a pain to track down, and fix. Good luck!

(Never looked at one, so it may not)

[BassmanPaul]

Not knowing the amplifier, if the amp has a tube output stage and he just changed out the tubes the bias could be way out for the new tubes. Normally there is a fuse to protect the tube section which could have blown removing the high voltage. The amp would look as if all is normal but it will not work.

I endorse Sam's recommendation for a trip to the tech.

Paul

[RickenBoogie]

It's uranium then, to the tech the amp should go.