My HD-130 with phase inverter tube was just repaired in two stages. Many, but not all caps were replaced. Rebias. New tubes, including the phase inverter tube, which was probably original. I played one gig with it. I practiced for the gig. Yesterday, I am practicing on the full power setting and the amp had probably been on continuously for four or five hours. There were complaints about the sound of my ES-335 through the amp from friends in the audience at the gig, I think that it was too harsh, so I am changing lots of settings in my multieffects pedal. After a lot of practicing and switching of guitars (the four of five hours of continuous use), at one point no sound is coming from the amp and I notice a burning smell. Then I notice that smoke is coming out of the back of the amp, it's coming from one or more of the output tubes. I turn the amp off. I run to read this forum about smoking tubes and read that it could be something as simple as a faulty input jack (in this case coming from my multieffects pedal, and the cables I get here are crummy). I wait 20-30 minutes. I change the external transformer I had been using and the input cable to the amp from the pedal, I turn the amp on at 65 watts, and it seems to sound fine and is producing the volumes I expect. The tubes barely appear to be on, whereas they were glowing orange and very hot when the smoke was being produced at the full power setting. I turn the amp off and go to sleep.
Is it safe to try the amp at full power, or should I immediately take the amp back to the tech who has been working on it? I have already spent about 400 euros, close to $550, on repairing this amp. That's a sunk cost, but this is very disappointing. It's not just the money. I live in rural France, and it's a major hassle to get the amp to the tech and back home. I am thinking about getting a new amp, though I don't gig so much that it was a pressing issue. I played for an hour on a Fender Super Deluxe III (not a common amp, it seems to have been phased out, but this guy has at least two of them) in a shop in Toulouse a few days ago, and it seemed very serviceable, so I am interested in getting a new amp, one that is less heavy and won't require an external transformer. But I was also hoping to get a few years use ouf of the Musicman while trying to figure out exactly what I want/need, which is not easy to do, because it is not easy to do A/B tests on amps in my part of France (and not that easy anywhere, probably) and I might want to buy a fairly exotic rig and have it sent to me. However, the main question now is, can I test the Musicman at full power, or do I need to take it immediately to the tech? I realize that one or more of the new tubes could have been defective.
Update: I have just played for over an hour at low-power (65W) but at sufficient volume to play the sort of gigs I've been playing. No problems, it sounds good, no smell, no smoke, no overheating. I've put it on Standby and will try again later.
Overheating
It honestly sounds like whoever "biased" it got it WAY to hot. Are you sure he didn't adjust it like a Fender amp and set it around 35mA? It kind of sounds like it, since you can run it on low and it's OK, AND you say the tubes glowed orange. Sounds way too hot. DO NOT run it on high unless you have it tested PROPERLY. Also, you say you have an EXTERNAL TRANSFORMER. Is this some kind of export amp? Are you using on 50hz power? Step down transformer? Step UP transformer? Which. Mike.
Overheating
I'm in France. I'm going from my 110-V American amp to 220. And it's at 50 Hz now. I personally exported/sent the amp to France with the rest of my belongings when I moved here. I've got a lot of transformers to go from 110 to 220. I don't know whether these are called step-up or step-down, but they typically only go in one direction, from 110 to 220. I have a few that are bidirectional. I was not using one of those.
My thought, after this incident, was also that he did not bias the amp properly, although he assured me that he had done it according to the original Musicman specs. He says that he works every year on the 410 Musicman for a guitarist who tours with Johnny Holliday, who is the biggest thing in French rock/pop, he'd be like the Rod Stewart of France. The tech seems to know what he's doing, he certainly thinks he knows what he's doing, but this whole thing has been a nightmare. I must reiterate that I know nothing about electronics, but after reading some stuff about bias, I also formed the hypothesis that he had screwed that up.
Step Down... Quality Tubes... Return to tech...
If you are in France then you are not going from 110 > 220, it's the other way around. A step down is required that takes the France power of 220 and cuts it to 110 so the amp will run. The first thing I would do is make sure the voltage is in the ballpark. Make sure it is converting to 110v-120v, not in the range of 150v. A simple multi-meter would be up to the task.
Next - you said the problem exists in HI mode but not LO mode. In HI mode that amp puts about 700v on the tubes, and not all tubes are up to that task. In LO mode the amp puts around 450v on the tubes, which is something they expect to see. I take it this is a 6CA7 (EL34) model. Unless you are running some really good NOS tubes, (some people have had success with new JJ-EL34L tubes as well) I recommend you run the amp in LO mode. Basic Chinese tubes are not going to be able to keep up.
Lastly - if you got the amp repaired in France and that person is suppose to be knowledgeable of Music Mans, why not take it back and ask them what is going on. Surely they won't charge you for a simple follow up after doing 400 euro's worth of "tune up"... If they do - find a new tech.
Just my 2 cents...
Update to Urgent Request
Thanks to all those who replied to me.
I spoke to the tech on Tuesday. He said it would be OK to test the amp at 130W and to keep him informed about what color the tubes are when I am playing. The four output tubes are orange at 130W, and I see no difference among the tubes in terms of how lit they are. They are hot, but not nearly as hot as when one or more was smoking and I wrote the original urgent request. At low power, the four tubes are faintly blue, they are not even obviously lit. The amp can still produce a lot of power at 65W.
I have the idea now that the problem was the step-down transformer I was using. I am surprised that the amp works at full power, but I've played for about 1/2 hr straight on it at the 130W setting without any apparent problem...so far.
If you cooked one tube, I
If you cooked one tube, I would suggest AGAINT using it on high at all. That tube MAY have melted the insides a little and it may sag and touch another plate. If you are going to use it use it on low. If they are ORANGE and brightly ORANGE, that is probably not good. A nice faint blue is a good sign. Especially true if using current production tubes. Mike.
Over Heating Gone Bad - Johnny Winter Vienna 2009
This can happen...Johnny Winter , November 2009.
http://www.youtube.com/watch?v=AXi0o5RiZg8