help please! Lonestar problem at the gig last night

I'm afraid I did some damage but I can't be sure, and I don't know what to check. I haven't used the SOLO feature in months, but when I stepped on the footswitch last night to engage the solo, I got a loud crackling sound (like when you touch the end of a live guitar cable) and an immediate burnt plastic smell. I was getting a little bit of signal but certainly not "SOLO'D".

After 5 seconds, I disengaged the solo, and played the rest of the song with no trouble. Turned the amp off after that song. 1/2hr later, turned the amp back on, after the gig, and everything works fine, including the solo.

I had the amp laying on the ground, using a roll of duct tape as tilt legs. So, basically it was almost 90' facing the ceiling. Maybe I overheated it? This bar is so small and the owner cries of loud volumes, so that was why I tried that. Never again.

What can I check to ensure my amp is really ok? TIA.

OK now the amp died altogether. I played 4 songs with it at tonight's gig and it shut off. Replacing the power tubes did nothing ... this won't even turn on now. Any ideas what I cooked?

Step one: Check the fuse.

So did you change any tubes after the first nights problem? A tube can go nuclear and then recover (usually by switching the amp off and back on), but the tube is still going bad and needs replacing...

I had crackling and reduced power and also the burning smell, but I had a quick look at the tubes and saw which one was red plating before I switched off. Once replaced the amp was fine.

Change the rectifier tube....5Y something.

When my LS died it was because of that tube alone.

Thanks guys. At the end of gig #1 I didn't check the fuse, because the amp recovered. After gig #2 last night, I checked the fuse onstage in poor lighting and it looked OK. Today at home, upon closer inspection I found 2 things. 1, the fuse does look ratty. Not broken in 2, but not brand new either ... some of the outer coatings are flaking off inside. Also, one of the center 6L6s has some black on the glass. I'll throw some spare tubes in the center position and later today I'll try and find a replacement fuse (hopefully Radio Shack has 'em).

The rectifier tube doesn't look damaged, but I can't be sure.

Do you guys think my amp might be OK, because the fuse stopped any real damage?

Mine worked fine, even after burning fishy smell. jjboogie's right, the "rectumfryer" tube is a big suspect....

Black or silver on the inside glass is normal. A white powder or white coating indicates blown-ness.
If the amp won't turn on at all (no pilot lamp), the fuse is the first thing to check, because that's what the fuse does - it cuts the A/C, mostly to prevent further damage. Merely replacing the fuse doesn't indicate the problem is solved, however. Be absolutely sure the replacement fuse is the correct value. It's very common for idiots (not you, a previous owner) to try to cure blowing fuses by installing a larger value.

Thanks for all the help so far. UPDATE! I replaced the fuse with the exact match= 4amp 250V slo blo. I also replaced the 2 center 6L6s. The amp turns on now and works fine. I am so happy.

NOW. I'm still considering having a Mesa Authorized tech give my amp a complete inspection. What I want to try next is putting the 2 "suspected bad" 6L6s in there again and see if I can recreate the problem. In theory that would make me feel better, since it would show me that the tubes in fact were the culprit. Do you guys think I might be tempting fate, and risking damage to more than the new fuse? I bought 12 fuses, so I don't mind killing one, if it helps me diagnose this.

Thanks so much!

Whoa! Before you do anything, first be sure the BIAS SELECT switch on the rear panel is set to "6L6".
If you want to test the 6L6 pair not currently in the amp:
Switch the amp to the "50 watt" setting.
Install the suspect pair in the OUTSIDE sockets. Only the outside pair is used in the 50 watt setting. But leave the inside pair in the amp.
In the 50 watt setting, you can also switch back and forth between the solid state and tube rectifier.
All this info is available in the manual.

Thanks again. Yes I always have it set to 6L6 - never EL84.

I put the bad tubes in the outer position, set it to 50 watts and my wife played my strat while I watched the tubes in action. The suspected bad tube started out glowing less than half as brightly as the other 50watter, and it just grew more dim every few seconds. Within 1 minute it was barely glowing at all, so I turned the amp off & swapped in 2 good tubes again, for a total of 4 healthy tubes. I now have more clean headroom, alot more volume and no trouble so far.

Thank you all very much for your help and your time.

UPDATE - I killed it again. 2 new tubes and I was cruisin along just fine for a while, but now I've managed to burn up another fuse, and shut the amp down. To the authorized repair center she goes.

Maury said:

UPDATE - I killed it again. 2 new tubes and I was cruisin along just fine for a while, but now I've managed to burn up another fuse, and shut the amp down. To the authorized repair center she goes.

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Did you try the Rectifier tube yet? Try that too before it goes to the repair center.

Try it whether or not it looks bad.

No, the rectifier tube is the only one I don't have a spare of

Maury said:

No, the rectifier tube is the only one I don't have a spare of

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Those are the ones that are NOTORIOUS for being the culprit too!

My guy at Mesa said at one time there was a batch of amps that went out that unfortunately had some not so good Rectifier tubes in them. I was sent a few spares.

Sorry you don't have one.....you might wanna buy one and try that first before you pay some bigger bucks on having it serviced.

You can always get the tube try it out and if it solves the problem great! If not you go get the amp fixed and you have a spare rectifier tube!

I hope you get it worked out soon though cause it really sucks having a sick amp at home!

I can appreciate that, but I have to drive the same distance - over an hour - to either buy a tube or drop it off for repair. Good news is the amp is under warranty until July of this year.

Generally speaking, if it's the rectifier tube that's gone you'll lose sound on 5W and 15W, but retain sound on 30W as it uses a solid state rectifier at that setting.

UPDATE: Musician's Electronic Services in Ardmore PA turned my Lonestar around in 1 week's time. He replaced 4 6L6s, sold me a rectifier tube (so I have a spare) and cleaned up some questionable solder joints. I'm looking forward to getting it back today and I must give MES 2 thumbs up!

Het Maury,

Any updates?