What causes a tube amp to fart out?

[Teh]

I was playing my new HRD III (about a month old) tonight at a low level (about '2-1/2' on a scale of '12') when I noticed it was slowly losing output power. It dropped to about 25% of the original volume, so I turned it off for a few seconds and then back on. It came back to full volume and worked fine the rest of the night. Wasn't doing anything crazy as I was testing out a new reverb pedal. Running through the clean channel, had a little compression, delay and reverb, and the OD pedal was used intermittently. Was certainly not overdriving the front end with what I was doing.

What would cause this? Bad tube? Flakey power transformer?

[django49]

GAS?

More seriously, if it is a NEW amp I would not expect that. It would not hurt to swap out some tubes to see if the problem goes away. I recently had a somewhat similar thing happen, which was traceable to a bad resistor(s) in the circuit. Which was, apparently, occurring when the component overheated.

But the LAST thing I am is an electronics-minded person......

[Armitage]

If it's a month old take it back for service.

[Steve Haynie]

Maybe a capacitator came loose. Get a screwdriver and tighten them things back down.

Seriously, though, try checking to see if a tube is knocked a little crooked. That would be an immediate thing to check. Try the amp again with a different guitar and cable to see if it will do it again. I had a Fender Prosonic head that had an intermittent problem like the one you described, and the person who fixed it spent a lot of time tracking down the source of the problem.

[bubs_42]

Its a Fender, return it and get a real amp. Take it back where you bought it for service after you check the Power Tubes.

[cmatthes]

Chipotle tubes.

[Teh]

thanks for the info. I've got it heating up in standby mode for a few hours this afternoon and will give it another play tonight. I've read about crap resistors overheating being another cause of volume drop, so we'll see if that might be it. I'll have to order the 6L6 power tubes to swap them out. I have a few spare 12ax7 laying around the house, so I could swap them as well. I've got over a week before the next gig, so there's time to figure it out.

The frustrating thing is the friggin' amp is only a month old. Intermittent issues SUCK!

[Feynman]

They'd probably just mail you a new one under the five year warranty. Let them figure it out.

[it's me HHB]

This is why I avoid cheaper PC board amps. They all down this sooner or later. Get a Tophat

[bubs_42]

They'd probably just mail you a new one under the five year warranty. Let them figure it out.

I won't buy a fender amplifier, its not going to happen and that goes for just about any China Built amplifier. Even the *ender made in "Mexico" from my understanding aren't if you know what I mean. More like assembled in or are they????

[Teh]

I re-seated all the tubes last night and gave it a thorough workout. Turned the output gain down on a couple of the modulation pedals at the end of the chain to present a lower signal to the front end input, then turned up the volume of the amp. Didn't have any problems, and sounded great. the more I dig into the problem, it may well have been operator error. I'm still planning on replacing the tubes with better quality ones, and may go with 12AT7s in the front end to provide a little more clean headroom. If it craps out again in the next couple months, then I'll take it in for warranty work.

They'd probably just mail you a new one under the five year warranty. Let them figure it out.

I won't buy a fender amplifier, its not going to happen and that goes for just about any China Built amplifier. Even the *ender made in "Mexico" from my understanding aren't if you know what I mean. More like assembled in or are they????

I dunno about that, Bubs. IMO, you gotta take the good with the bad. In my case, I really like the sound of the Fender. The clean tones are what I like to hear from my guitars - nice and full on the low and pristine but not harsh highs. Without any pedals, the amp makes Teles and Strats sound like a record, and worked out great last weekend with the full hollowbody jazz box. The spring reverb is good quality. And it's quiet -- virtually no hiss or noise. The overdrive channel isn't the best, but for a little grit it's passable. The pedalboard more than makes up for this deficiency.

I've had an Egnater Rebel 30 for the past few years. Frankly, the Fender makes the Egnater sound like a Radio Shack speaker housed in a shoebox. The Egnater has better overdrive, but that's the only advantage -- Which has been neutralized by the OCD pedal. The Fender's advantage really comes through when running with a little chorus and delay, or a Strat straight up with a little compression and reverb, or a humbucker with a little dirt from the overdrive pedal. Great classic rock sound.

Putting this all in context -- I am in no way an expert on amps or electric rigs but, to be fair, I only play a handful of gigs a year that require this kind of gear. I spend most of my gigging time playing solo acoustic shows or in a folk/rock/pop acoustic group. I'm a lot more comfortable working with my acoustic rig (Bose L1). There are lots of amps I'd love to get my hands on (the Top Hat is one), but I can't justify spending the money for the high end when the Fender covers the bases nicely at half the price.

Now, guitars are another discussion altogether...

[Teh]

Update: Stopped by GC tonight on the way home from the airport. Explained the issue, and the salesman immediately walked over to the computer and ordered a replacement. should be here in a week or so. No pain, no strain...

[Biz Prof]

Chipotle tubes.

My potty humor radar must be malfunctioning. It took me about 48 hours to get this one. ;-)

[Armitage]

Update: Stopped by GC tonight on the way home from the airport. Explained the issue, and the salesman immediately walked over to the computer and ordered a replacement. should be here in a week or so. No pain, no strain...

The right thing to do.

[Roshark]

I had a similar problem with an 80's Artist Marshall head . Very intermittent and very difficult to trace . It turned out to be a faulty solder joint on one pin of an output tube .

[Teh]

Picked up the replacement amp this afternoon. All is right with the world...

[Hfan]

Good for you. Good to have spare tubes around as well. If something goes south at least you can eliminate the tubes as a cause. Swap em one at a time.

[Caddie]

Don't waste your money on new tubes. It works now, right? Most tube amps spent a lot of time in unGodly humid warehouses. Then in a shipping container crossing the Pacific. You took the tubes out of the sockets, that in itself wiped the corrosion off the pins & sockets. There ya go! Or you could take it to some self proclaimed tube amp guru and $200 later you'll walk out cursing Fender.

Question #2) I can here it already, "How do you bias this thing?" Get on line and google "how to bias tube guitar amplifiers"

Make sure you unplug it first. Unless you want a new hairdo,

Cheers!

caddie

[Teh]

I've been playing the snot out of this amp since I picked up the new one last weekend. Sounds great, not going to touch a thing. I've got some spare 12AX7s from when I swapped the tubes in the old Egnater, just in case they're needed.

Re: Biasing -- I re-biased after the aforementioned tube swap. Not a big deal. I'm getting my dirt from the OCD on the pedalboard and the clean tone is sweet as is, so no reason that I can think of to tweak on it now. Down the road I may do some probing and twiddling but, for now, life is very good!

[Caddie]

Chipotle tubes.

My potty humor radar must be malfunctioning. It took me about 48 hours to get this one. ;-)

I still don't get it but I'v never been to Chipotle.

[Armitage]

Me neither...