crackling noise

[Waspination]

I have a Mark IVb from 2001. Ive had for about 9 months. Here and there I noticed some crackling when i play but it goes away. Its most noticeable on channels 1 and 2. When i tap the speaker jack i hear it crackle. Recently i noticed it crackles a lot more when I switch to class A, and if i touch a power tube and just barely wiggle it, it will crackle.
SO was checking here if anyone with experience could help me out. Is it just my tubes cuz that be fine with me... my concern is if its something internally.
Lets say it is and i get it serviced, whats a price range of getting it checked and fixed?

p.s -Also channel 3 hisses but i thought its supposed to cuz its at such high gain and i dont have the best guitar, but is there supposed to be no hissing at all?

 

[screamingdaisy]

Channel 3 will hiss. If you turn the volume on your guitar down to zero it will give you an indication of how much of that hiss is originating at your guitar.

As for the rest of it, the crackling sounds like a tube that's mechanically failed. Basically, something on the inside of the tube has come loose and will short things out when it vibrates the right way. The way to confirm this is to tap each tube and the tube that crackles is the defective one.

 

[Waspination]

Channel 3 will hiss. If you turn the volume on your guitar down to zero it will give you an indication of how much of that hiss is originating at your guitar.

As for the rest of it, the crackling sounds like a tube that's mechanically failed. Basically, something on the inside of the tube has come loose and will short things out when it vibrates the right way. The way to confirm this is to tap each tube and the tube that crackles is the defective one.

I just played on it and low volumes it is fine. When i crank it up, and it vibrates more, it crackles, pretty bad when i hit the string hard and it almost sounds like its cutting out.
It seems to be any power tube that it crackles. They look fine though. any chance it could be a preamp tube?

 

[screamingdaisy]

It could be. When it happens to me I tap all of them just to make sure.

 

[boogiemon]

sounds like a pre-amp tube to me.

 

[Waspination]

sounds like a pre-amp tube to me.

I Hope it is
Here just made a video to see whats goin on. Image this cutting into your sound, It tears the first two channels up bad but the 3rd seems fine. I did this all in channel 2. I didnt tap the preamps on here but it does the same thing as the power.
http://www.youtube.com/watch?v=nMmRI22y4k8

 

[boogiemon]

ok, that *doesn't* seem like a bad pre-amp tube problem: maybe a loose ground wire somewhere.

good luck.

sounds like a pre-amp tube to me.

I Hope it is
Here just made a video to see whats goin on. Image this cutting into your sound, It tears the first two channels up bad but the 3rd seems fine. I did this all in channel 2. I didnt tap the preamps on here but it does the same thing as the power.
http://www.youtube.com/watch?v=nMmRI22y4k8

 

[Scary]

It may not be the amp at all, is it possible something in the FX loop is going into clip?

 

[Waspination]

It may not be the amp at all, is it possible something in the FX loop is going into clip?

but i dont have it on. Wouldnt it not affect it if i have it off?