Roadster smells like fire!- please help

[alex1fly]

I've read through the manual and I think I know what the problem is, but I'd like to see what you guys think about it.

I was using my Roadster at practice last night in a college house that is not electrically grounded (but no rain or anything). After a minute or so of being on it popped and shut off. The fuse was blown and there was a funky burning smell. Got some more fuses, blew two more and decided to call it a night; this time however, the amp made a really loud noise while in the "On" position (not in Standby) before it turned off again. Read in the manual, checked out my power tubes, found that one of tubes did indeed smell like burnt material and its particular socket had black residue on it. The tube in question was on the far right, farthest from the Input jack. Does this sound like a simple power tube short? Is it okay to put my stock tubes back in and test it with the residue on the one tube socket?

I should add that I'm using EL-34s and for about the first 30 minutes of their use I hadn't set the Bias setting to EL-34, but I did that and used for a couple of weeks before this happened. And last week the amp was making some softer crackly noises that I just attributed to a bad cable. Thanks a bunch!

Alex

 

[AdmiralB]

You've probably arced that tube, from plate to heater. DO NOT turn it on again, there are probably burnt components inside.

 

[fishyfishfish]

Do what the man says!!!!! It's time to go to the repairman, it sound like a blown power tube. I had the same experience with my Lone Star. Mesa fixed it right up!

 

[alex1fly]

It would be sweet if I could just replace the power tube. There aren't any real techs in my area and shipping the amp to Mesa may take too long- I have shows coming up! I am worried about other damaged components like the tube socket itself or the transformers...

 

[AdmiralB]

The carbon trace on the socket will conduct. Even if you repair the internal damage (and I guarantee that there is internal damage), the next time you power it up, it'll arc again.

You have to replace the tube socket; *sometimes* it's possible to grind off the track, but not always.

The way Mesa fuses their amps (slow-blow mains, no HT fuse) guarantees that you will have internal damage when this occurs.

 

[alex1fly]

Well ****. I guess I really do need to take it to a tech. Can I take it to any tech or does that void the warranty; are authorized Mesa dealers also Mesa techs or will I need to ship my amp out to Cali?

 

[francric]

Call Mesa customer service. They will give you the name of the closest Mesa tech in your area for warranty work. Going to a non authorized tech will void your warranty.

 

[Travis]

I had a preamp tube explode in an amp, fuse blew too. New tube new fuse and no more problems.

 

[alex1fly]

Found a Mesa tech, took it to him (120 miles of driving : boo!), and he was nice enough to take a look at it that day! He said its probably a resistor and the socket. It will still be some time before my tubes arrive. Thanks everyone for helping me out!

 

[Crikey]

a bit off topic, the band had just got a smoke machine, only the bass dude and myself knew.
I set it up behind the other guitarists amp stack and set it off, I also had a small firework cracker handy After the cracker went off they saw the smoke , the guitarist went white, I have never seen so many blokes running around so quickly disconnecting power leads :lol:
After calling me everything name under the sun they finally laugh about it.

 

[mrd]

In other news, why the heck did you plug in a high-end amp into an outlet with no ground? :shock:

 

[Dusty Rhodes]

In other news, why the heck did you plug in a high-end amp into an outlet with no ground? :shock:

+1

 

[alex1fly]

In other news, why the heck did you plug in a high-end amp into an outlet with no ground? :shock:

Because I don't really have a choice; in my crappy little town you practice wherever you can, which means ungrounded college rent houses built in the 1940s. These outlets are two prong and even the adapters you can get just fall right out of the wall. Sketchy, I know, but I love to play with people I've been doing it for almost 2 years now without any problems.

Would it be in my best interest to take a surge protector/power bar to practice?

 

[rvschulz]

depends if you want this to happen again. if i was in your power situation, i would bring a power conditioner and UPS to be sure i have a cleaned-up source and a filter for surges.

no matter what, i always plug power through a surge protector. period.

 

[AdmiralB]

This had absolutely nothing to do with grounding. He arced a power tube, probably from a mismatched load.

 

[AdmiralB]

no matter what, i always plug power through a surge protector. period.

If you're using a Mesa amp, you already are. All of them have MOVs on the mains, which is all a surge protector is.

 

[AdmiralB]

if you read the Mesa catalog, they talk about "varistor" which is a built-in surge protection component in the circuitry/board. Maybe Admiral Man is referring to the same.

Yep, MOV=Metal Oxide Varistor. It's a resistor whose value varies with the voltage across it. Typically here we use 130V units - they have extremely high resistance at 130V but above that the resistance falls quickly, so they "short" with surges, passing the current through themselves rather than whatever is on the circuit they're attached across.

If you open up your garden-variety surge suppressor, it's just an outlet strip with an MOV across the terminals. Mesa puts them in all their amps at the AC inlet.

Note that all you need is one of them on a circuit, so if you have one plugged into your wall, everything else on that circuit is covered by it, whether you actually plug into that strip or not. And when the 'protect', they usually die, so they're 'one-shot' devices for big surges.

 

[mrd]

This had absolutely nothing to do with grounding. He arced a power tube, probably from a mismatched load.

Yes, but plugging in without a ground is just a bad idea anyway. That's how you get electrocuted. Power-bars aren't gonna fix anything. If the house isn't grounded, you run the risk regardless of whatever fancy equipment you use. Personally, I would stop. But if the urge to play overpowers you, then I guess play.. but hopefully you don't get shocked.