I think I screwed up my amp...?

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Myriad_Rocker

Myriad_Rocker

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So I was tracking guitars today with the other guitarist in my band. We have the cab downstairs and the head upstairs. It's a Mesa Dual Rec and a Mesa 4x12, by the way. I have a 100' Pro Co snake running from the downstairs to the upstairs. The cab is plugged into the snake, which is then plugged into the head upstairs.

We were tracking guitars and stopped. When we started back up, there was no sound. I look over at the head and noticed that it was off. I had blown a fuse in it not more than a few months ago. It was because my cab came unplugged from my amp. I had replaced the fuse and all was well. So, I pulled the fuse out and there it was...black and obviously blown. I replace the fuse and take the amp downstairs to plug into my cab because there was no way that I was going to use the snake anymore to connect the cab to the head.

When I plug the head into the cab and turn it on, there is just crazy amounts of static and pops. This static and popping is not present on the clean channel. I looked in the back and notice that the two power tubes (not recto tubes) on the far right are glowing more than the first two. And when I turn the standby switch to the off position, it makes a loud pop. I let the tubes cool down a bit and put my fingers on the first two. They're kinda warm but I can keep my fingers on them. I touch either one of the next two and they're so hot that there's no way you can keep your fingers on them.

So...I have some old tubes and I was thinking about swapping the power section out with my old tubes to see if I messed up the tubes. If that doesn't work, then something larger is wrong.

Any ideas?
 
The staticy popping smells of screwed tubes to me. But I may be wrong.
 
legionserial said:
The staticy popping smells of screwed tubes to me. But I may be wrong.
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That's exactly what I thought. I just got done swapping out the power tubes to my old stock ones. It's still doing it, though. I'll check the preamp ones as well and see if anything changes.

If not, well....looks like it's going to the shop. Hopefully it doesn't cost me an arm and/or a leg to get it fixed.
 
You were using a stage snake for a speaker cable? They are two completely different types of cable. No wonder you fried it.

I am not an expert, by any means, but I think that usually zaps your transformer or something else equally expensive...
 
What possibly happened is that the small wires in a snake overheated amd melted the insulation resulting in a short at the output of your amp.
That's very possible and if so, you probably took out something in the output section ..... or possibly in the power supply but most likely in the output..
Good luck ...... hope it's cheap.
 
(in my best eastwood) "well do you fell lucky...." if ya are it's just some output tubes... if your not add an output transformer..... the fuses go real quick or take a few seconds???? take the output tubes out and try it... still blow fuses???? if so ya probably have a new output tranny in your future...
 
I bought a display model 6505 and when I got it the preamp tubes were worn out. They weren't completely dead, just old. I was getting a fair bit of pops and static but nothing on an enormous level. So it might be worth trying retubing the preamp section. The main problem was that I wasn't getting anywhere near enough distortion even for recording with the pre gain all the way up.
 
Lt. Bob said:
What possibly happened is that the small wires in a snake overheated amd melted the insulation resulting in a short at the output of your amp.
That's very possible and if so, you probably took out something in the output section ..... or possibly in the power supply but most likely in the output..
Good luck ...... hope it's cheap.
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No, that wire has to still be good because I used it for a headphone feed later on when we moved the guitar heads downstairs with the cabs.

dementedchord said:
(in my best eastwood) "well do you fell lucky...." if ya are it's just some output tubes... if your not add an output transformer..... the fuses go real quick or take a few seconds???? take the output tubes out and try it... still blow fuses???? if so ya probably have a new output tranny in your future...
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I'm going to try the preamp tubes today. The thing is, the power amp tubes are okay when the power is on and the standby is off. They they become blue when the standby switch is flipped up.

Also, the fuse doesn't continue to blow. Once I put the new one in, all was fine....except for all the loud static and popping.



If it's the output transformer, that'll set me back $275. If it's the power transformer, it'll be about $300. Is it more likely to be the output transformer or what?
 
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amra said:
You were using a stage snake for a speaker cable? They are two completely different types of cable. No wonder you fried it.

I am not an expert, by any means, but I think that usually zaps your transformer or something else equally expensive...
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Same thought came to mind when I read this. I'm guessing that the transformer is toast. Likely that it first fried your snake and then the output transformer.

Take it to a shop.
 
punkin said:
Same thought came to mind when I read this. I'm guessing that the transformer is toast. Likely that it first fried your snake and then the output transformer.

Take it to a shop.
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Like I said, I used the same cord from the snake to do a headphone feed later and it worked fine.
 
Myriad_Rocker said:
Like I said, I used the same cord from the snake to do a headphone feed later and it worked fine.
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Yeah but your amp puts out a lot more than that headphone amp ........ so it can arc at some weak spot in the insulation even if the headphone amp doesn't; so as far as your amp would be concerned ..... that'd be a short even though the lower powered headphone amp works fine thru the same snake.
I'm not saying that this is definitely what happened with your amp. But this is one of the reasons why you're not supposed to run speaker type signals thru a snake or even a guitar cable.
You'll have a better idea what it was when they find out exactly what's messed up.
 
Over the years I've had a number of amps go bad. Unfortunately, the problem was almost never a tube.

Good luck.
 
My vote is you fried the transformer along with the tubes
the good news is that it will cost less to repair than it will to replace seing it is a Mesa.
i think you learned a valuable lesson about using a snake as a speaker cable.
Snakes should only be used as a signal sends to the mixer input not as speaker cables.;)
 
i work on tools and small components, unrelated but yet related to audio.

and shorts are very common to fry things, and shorts due to the breakdown of insulation is tricky, as it can work/insulate fine under small current conditions and then short-out during high current conditions....the wrappings of the fine wire in a transformer, with extremely fine insulation covering the fine wire of a transformer is a good example.
These thousands of fine wrapped wires around the magnet, may short only when running hot, or hi amps...yet be fine when cool and low current.

and of all the thousands wraps of wire...it only takes one spot to short out.
A transformer mfg tech support said Lightening strikes and spikes are common to degrade the fine-thin insulation of transformer winding wires.

tricky stuff... repairing things and spending money only to have them short out again when the system is using Hi-current is a bitch.
 
Snapping and popping could be some low-level arcing across a tube socket, more likely a fried cap or resistor. It could even be the output trannie, but since it's not blowing the fuse, probly not.
 
Roguetitan said:
My vote is you fried the transformer along with the tubes
the good news is that it will cost less to repair than it will to replace seing it is a Mesa.
i think you learned a valuable lesson about using a snake as a speaker cable.
Snakes should only be used as a signal sends to the mixer input not as speaker cables.;)
Click to expand...

AMEN:

Speaker cables are not some type of gimmick they are absolutely necessary on a power amp. A valuable lesson from the school of hard knocks indeed.
 
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Myriad_Rocker said:
If it's the output transformer, that'll set me back $275. If it's the power transformer, it'll be about $300. Is it more likely to be the output transformer or what?
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Uhmm this probably wont help but I have the old output transformer from my Marshall TSL. I don't suppose they're interchangeable but on the off chance that they are, you'd be welcome to it. Weighs a ton though and the shipping cost would be massively expensive.
 
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