#1
Hi, this is my first post.

I have a Mesa Stiletto Ace combo (greatest rhythm amp I've ever heard, not bad for lead when boosted) and it recently died. I called Mesa and they said it's probably that my power tubes have finally gone (2-year-old amp, original EL34s) and Groove Tubes said the same thing. I got a matched pair of GT EL34Ms just tonight, put them in, put a new fuse in, and turned the amp on. The amp turned on. I was able to use the clean channel (on Spongy) for a while, and then I wanted to try out Channel 2.

I press the footswitch to change channels, and I get about two or three seconds of distortion until the amp dies yet again. At first I think that maybe the tubes weren't quite warmed up yet, but when I swap the fuse out again (I'm using the right fuses - 3A, 120V or greater) and it blows my last fuse as soon as I turn the amp back on.

I'm hoping someone here will know what's up with my amp, since I don't want to get a new one...
#4
id consider taking it to a local guitar shop or specialist and let them check it out and diagnose. If worse comes to worse, send it to Mesa and ask for a new one. They should understand, and the warranty should be good
#5
Yeah, bring your guitar in to a tech because if you have no experience with tubes, you shouldn't try to re-bias the new ones right off the bat without any experience.
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#6
When you say it "died"... did it turn off, did a fuse blow, did sound just stop coming out, or what?
#7
When I said "it died" I meant that the fuse blew, and the amp no longer got any power. I'd think it would still work with a good fuse.
#8
^Eugh, bummer. I'd give Mesa a call and let them know what happened, the first time could've been bad tubes but this time almost certainly wasn't.

I'd be quite pissed if that were me, though... that amp's absolutely amazing IMO.
#9
Mesas dont need to biased theyre cold biased already Im pretty sure.

Also make sure you take it to A MESA CERTIFIED TECH otherwise it will VOID the warrenty.
#10
Try a different type of fuse first just to be sure.
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#11
Yeah, I was probably just going to take to GC. They're the only place I can think of around where I live that is an actual Mesa retailer.

And I know that my amp is supposed to be "Fixed Bias" - is that what you mean by cold biased? The tubes sounded just fine when I was getting sound out of them...

And it's the right kind of fuse - it's the same kind that was in there before, the same kind that Mesa recommends. You can see below that it says "3A Slo Blo" - that's exactly what I have. Slow-Blow fuses have a coil wrapped around a center post, as opposed to fast-acting fuses, which only have the center post and that's what disintegrates.

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Last edited by dwsabianguy at Jul 24, 2008,
#13
The glass? The tubes themselves (as far as I can tell) are just fine...
#14
Quote by dogismycopilot
Tube amps are horrible because they can break; cause of the glass, thats probably why.

this post is made of fail
tube amps can be a hassle when they break, but the tone is better 99% of the time
#15
you funny
(he was joking)

it seems like its a bigger problem than the tubes. perhaps a resistor's gone bad or something and the voltage is too high for the amp to handle, therefore blowing the fuse and maybe your tubes.
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#19
Quote by dwsabianguy
Yeah, I was probably just going to take to GC. They're the only place I can think of around where I live that is an actual Mesa retailer.

And I know that my amp is supposed to be "Fixed Bias" - is that what you mean by cold biased? The tubes sounded just fine when I was getting sound out of them...

And it's the right kind of fuse - it's the same kind that was in there before, the same kind that Mesa recommends. You can see below that it says "3A Slo Blo" - that's exactly what I have. Slow-Blow fuses have a coil wrapped around a center post, as opposed to fast-acting fuses, which only have the center post and that's what disintegrates.

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Yeah fixed biased is what I meant sorry.

Honestly Id take it to a tech or try here
http://forum.grailtone.com/index.php
I hate to link to another forum but these guys really know their stuff and can help you out, its a Mesa exclusive site so they know Mesa Boogie stuff.
#21
This sounds like a rectifier issue. If that amp has a tube/SS option, switch it to SS and see if that helps. If it doesn't, you'll need to take it to a tech since it's probably a rectifier diode or (hopefully not) something worse.
#22
The weird part is that the Channel 2 uses the Diode Rectifier, and Channel 1 uses the tube. I guess it's possible it could be the diode, but for some reason I doubt it.
#24
No, when the fuse blows, it shuts of the power to the whole amp.

And I'm just about positive it's not a recitifier issue, I got a little bit of play time and I was using the tube rectifier...
#25
Well, "play time" doesn't really mean that it's not a rectifier issue. It certainly could have died while you were playing.
But the fact that the light turns off means that it's something worse than just the rectifier. You need to take it to a tech.
Edit: Scratch that, try replacing the power tubes first. One might be shorted.
Last edited by Roc8995 at Jul 26, 2008,
#26
Quote by AthenasGhost
Yeah, bring your guitar in to a tech because if you have no experience with tubes, you shouldn't try to re-bias the new ones right off the bat without any experience.


...This logic is broked I have the same things going on, take it to a professional till you get some experience yourself, but how can i get experience unless I try for myself!? Oh noes!
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#27
A great way to get experience is to take it to a tech and watch him do it. That logic makes a lot of sense to me. Learn from a professional
#28
Seems like a few of you posted good info, it's just really not in any order to follow well.

1. 2 years old... the power tubes most definatly are reaching if not have already reached the end of their life. The preamp tubes are probably fried as well. I would order a new set of tubes from MESA or eurotubes so they will be biased specifically for Mesa's. Replace the fuse if blown. When you replace the tubes, let it run on standby for about 20 minutes and check the tubes to see whether or not they are redplating

If so immediatly shut off the amp and replace that tube. Always have 2 extra power tubes on hand. Tubes are like light bulbs, just because they're new doesn't mean they're not bad, which is why all brands have a warranty for at least the first month. Usually if a tube is going to go bad, it will die almost immediately.

2. If the amp is working but the cleans sound really distorted, the distortion sounds really weak, or a certain channel doesn't work, or reverb isn't working, a preamp tube, or more than one preamp tube is probably dead. Because they're 2 years old, I recommend replacing all of them. It doesn't matter which type or brand you use for preamp tubes, they all have their own characteristics, some desired, some loathed. I recommend JJ's or tung sols. eurotubes.com carry JJ's, he has high gain tube sets if thats what youre going for. Again, it never hurts to carry extras.

3. If you're still having problems, chances are it's more than a tube problem. Go to a mesa certified dealer/repair shop or mail it in to mesa.
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#29
Well, I put some new Groove Tubes EL34Ms in before I started this thread. And the guy that I got the amp from had replaced four of the five preamp tubes. But the power tubes were definitely going if not already gone. One looked flat-out terrible.

That being said, I will soon retube the preamp.

I got some more fuses today, and when I put one in and tried to turn the amp on, it immediately cut off. And the fact that the light cut off doesn't mean anything other than the fuse has blown and cut off power to the whole amp.

My preamp sounds fine, I don't have any microphonics, funny distortion, distorted cleans, or anything like that. My amp doesn't have reverb, either. I have a Holy Grail for that.

I really wish that Mesa was open for more than Monday to Thursday and that they had an email.
#30
No, the light can stay on if the fuse has blown. Look at a schematic. I was making sure your OT didn't blow up, which would result in the fuse blowing but the light remaining lit. This sounds like a shorted power tube to me.
#31
I called Mesa again today and the tech support dude said that it could be a screen resistor... Either way, I'm going to take it for service within the week.

What does OT stand for?
#32
ot = output transformer.
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