What the actual fuck is wrong with my amp?

[repoman]

I had a AC15 that started crackling and when I changed the power tubes it stopped.
It crackled mostly when turning up the volume knob, there was a tiny tiny bit of crackle if I played hard.

[Mudfuzz]

Tubes in bass amps tend to go microphonic because of the low frequencies at loud volumes making them vibrate [if you put your head on your cab].. most of the noise you hear from a tube bass amp that you think are preamp tube issues are actually power tube issues due to this.. You might need new tubes.. fuck... my mesa 400+ is still sitting unused because I either need to replace 2 bad tubes and off load the thing or buy 10 more fucking power tubes...

[Jwar]

I do set it on the cab. Maybe I need a stand or something.

I do have replacement power tubes, I'm just really bad at that stuff. Preamps are easy, the other I don't understand.

[Faldoe]

Good you seemed to fix the issue but next time maybe not just go spraying shit everywhere or changing the preamp tubes unless you know they are bad. Unless money is no object.

If you had issues with certain pedals I'd see if everything was fine with just a direct signal first. If it was, then it might be a pedal issue or like someone said the signal was overloading something, maybe a preamp tube.

I'd thinking if you took it to a tech before they would have cleaned the sockets anyways.

[repoman]

A way that you might find the culprit tube (if it is a microphonic tube causing the crackling) is to have the amp on and tap each of the tubes with the eraser side of a pencil (or something similar that won't damage the glass), it should make some kind of noise if its bad. They can make all sorts of weird noises when they become microphonic, besides crackling, they can make odd overtones, hums, honks, squeals.

If the amp is constantly eating powertubes its probably not biased correctly. I would think a set of KT88s should last many years before going bad.

[Iommic Pope]

This wouldn't have anything to do with that stupid fixed bias shit Mesa pull, would it?

[Jwar]

Good you seemed to fix the issue but next time maybe not just go spraying shit everywhere or changing the preamp tubes unless you know they are bad. Unless money is no object.

If you had issues with certain pedals I'd see if everything was fine with just a direct signal first. If it was, then it might be a pedal issue or like someone said the signal was overloading something, maybe a preamp tube.

I'd thinking if you took it to a tech before they would have cleaned the sockets anyways.

Haha. I was slightly exaggerating when I said I sprayed everywhere. I was very calculated on where and how I did it. Mostly I just sprayed out all of the jacks. Previous to that I had sprayed out the preamp tube sockets. I didn't do anything with the power tube. sockets. The preamp tubes were shit. I had new ones laying around and have some Gold Lion KT88's for the power amp when I need those replaced.

Yes you would think the tech would clean them, and who knows, maybe they did and they got some shit in them in transit. I have no clue.

Also, been through all the direct signal stuff before. That wasn't it. I wish it was a pedal so I could smash it with a hammer.

I'm just glad it seems fixed for now.

[Jwar]

This wouldn't have anything to do with that stupid fixed bias shit Mesa pull, would it?

No. This one you have to bias. That's why I'm afraid to do the power tubes. I had done it previously and fucked up a few of them.

[waltdogg]

it's not uncommon for an amp, even one that sees regular use, for it to collect dust and corrosion in the jacks and switches to cause what you were experiencing.

[elevenstrings]

Long ago, I used to have a roadcase Mesa 4x10 and 1x15 with a Basis M-2000 head.

What a piece of junk. I think I had to bring it back to Mesa twice before getting rid of it. Fortunately, their office/warehouse/factory was only about a 20 minute drive from me.