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A (somewhat long) tale of woe:I have a Jasmine Serenade Tube integrated amp. Several months ago I noticed that the sound field had shifted somewhat toward the left channel; the right channel still played, but at a reduced level.
I took it to a local repair shop where I had had successful work on various pieces done in the past. After 2 weeks they told me the problem was related to bad resistors related to the headphone amp and had been fixed. Ignorant as I am about such things, I brought it home. The only cost was the original diagnostic fee.
Unfortunately the channel imbalance, while not as severe, still persisted. I took it back, they agreed it wasn't right, and, after another 5 weeks, called to tell me it was now fixed and charged me just an additional $11.00 for the replacement of a couple of capacitors..
For a week the amp performed perfectly and in fact sounded even better than ever.
But here's where the plot thickens! Just before I took the amp in for repair the first time, I had ordered a pair of supposedly new Valve Art EL 34 tubes from someone on eBay. I got the tubes weeks ago, but didn't try them until today. Almost immediately after installation I noticed a slight crackling sound from the right channel, but nothing too serious-or so I thought. Unfortunately I chose this moment to go upstairs to grab a snack. (I probably should mention that as I was about to install these "new" tubes, I noticed some scuffing at several spots around the base; I attributed this to the possibility that the seller had installed them to check them out.)
When I returned a few minutes later, smoke was billowing around the right channel EL 34 and the cracking sound in that channel was much louder. I shut everything down and after it cooled off, replaced those tubes with a pair that I knew were working correctly. Unfortunately the right channel is deader than a door nail. The right channel speaker, however, seems to be just fine.
Since I'm relatively inexperienced with tube gear, I'd appreciate any and all opinions and/or comments about the situation I've described. Is the most likely culprit the repair having gone bad? Or a bad tube? Or...?
And finally, is it possible to hazard a guess about the type and/or extent of the damage this tube blowing up might be?
Thanks in advance for any responses.
Edits: 08/16/14Follow Ups:
Does your amp have auto biasing? I had a similar problem and found the tube shorted out the cap in the auto bias circuit. I replaced all four caps for all four tubes, and it has been great since.
Bob
It does have auto-bias. I suppose I'll find out what the issue is though after I take it to the repair shop. Thanks for the input.
Open it up and post photos of the damage.
Chinese amps come with Chinese tubes, which may have been part of the problem to begin with.
I'm taking it to a repair shop. I've used Valve Art and other Chinese tubes with various amps/preamps for years without incident until now. The problem, I'm quite certain, is that I was sold a tube that was defective, not the country of origin. Please note the details in my posts.
I had that happen with a pair of 45 globes once. The tube fried, the amp smoked and there was the sound of some part rattling around inside the amp. Blackdog is likely correct, my amp just needed a resistor replaced.
-Rod
Chances are your "new" tubes are not new or defective. You've probably burnt out the cathode resistor on that tube, so that tube is no longer drawing current. It shouldn't be an expensive fix, if that is the problem.
Hopefully it isn't more serious.
Lesson - buying tubes off Ebay can be dangerous. For Valve Art use
www.tubesandmore.com for other brands www.thetubestore.com
Dan Santoni
This is the first time I've ever bought tubes on eBay-and it will be the last. I've purchased frequently from Tube Depot and one other vendor whose name I can't recall at the moment and never had any problems.
Did you check the idle bias current of the new tubes? Sounds like right channel EL34 was drawing too much current and fried some of the circuit around it.You need to go back to the tech, for a complete inspection.
Sorry about the news. Good luck!
Edits: 08/16/14
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