bad tube with bizarre symptom

[daz]

Guess i'll toss this winged C el34 but i hate seeing another one bite the dust with the current situation at the russian plant. My amp sits a foot from a wall, so when i check the bias i tip it towards me about 30 degrees to get to the slotted bias pots. It's dual bias. So i decide to check it because you know how tubes often drift after a while. I set them the same, about 35ms. I then let it gently back upright and i go to turn off the meter and i see the one tube has gone way low, around 23ma. So i tip the amp again to adjust it and it goes up higher this time. i adjust it, let it back upright and it goes up to 44ma ! So i test it by tipping the amp and letting it back upright several times and every time i do the bias move way up when upright and back down when i tip it by 10 to 15 ma. I tapped it, moved it around, no effect. Tip the amp and it does it every time. Replaced it and the tube i replaced it with works fine so it's not that side either socket or pot or anything like that.

not really asking a question here as much as just thought it was a interesting story to relay. I have never seen anything like that before.

[Chuck H]

Good observational skills are a vital part of good trouble shooting skills. You probably saved yourself a lot of time by catching that weirdness early! That WOULD qualify as strange. But I've seen tubes do some strange things. So much so with new production tubes that even if I fire up a brand new build (even a one off custom design) and it has some problems I check the tubes first. Logic would seem to dictate that a manufactured item, like a tube, would be consistent enough that I should question my hand wiring first. But more often than not I find a problem with one of the NEW tubes!?! Must be part of why people pay out the nose for NOS.

One big problem is that I might take a few months getting to every aspect of a new build before I ever install the tubes. And the tube vendors only offer a 30 to 90 day warranty! I haven't yet disciplined myself to test all new tubes when they arrive. But it's starting to sink in. Up to now I just toss the bad, new tubes and replace them. Adding fifteen to forty bucks to the materials expense for my last three amps!!! Which really sucks when you've already taken a materials deposit from your customer. Then, to avoid looking like an idiot, I just have to eat the expense. Not that I make any real profit for my time, but when unforeseen expenses come out of my own pocket it sucks. If I sold product or services as poor as the tube vendors I'd either starve to death or be in jail. And that's not a joke! But these are the times we live in. So test all tubes (including tilting them apparently!?!) when you receive them. That way you at least have some chance of returning or replacing them before it becomes a schedule or money issue. It seems ridiculous that I need to do MY job to earn money to buy the tube vendors products, and then I need to do THEIR job and make time concessions to avoid losing money I paid them for a product and service!. That's just absurd.

[km6xz]

That is the sad situation now, premium prices for less than acceptable QC.
Buy from a vendor who accepts returns and box them once a month or two and send the fallouts back to them for replacement or credit. If they will not accept returns, find a vendor who will.
When I had my shop before moving here, we had a large box with padding where all the new-bad tubes went(which were not many actually a few a week) and Tom, the owner of Magic Parts/Ruby Tubes would come pick them up and issue a credit. There was no reason to even bother looking for another source with that sort of no-questions asked customer service. He built his business on good testing of every tube so we used a lot of tubes and had very few failures out of the box.
For a while we tried Groove Tubes but the policies and failure rate were poor. In fact I get a better rate of working tubes as bulk from China than I did with some of the "expensive brand names" which spent most of their QC budget on ads and promotion than bothering to check their products. None had as flaky and inconsistent matching as G.T., yet at the time, they were the most expensive.
I just got a stock of EH 12AX7s from the factory, and the first two used in customer units were bad out of the box. So I ran curves on the whole batch and found I have about 1/2 which are noisy, unbalanced 1/2s or failing to meet minimum gain requirements.
I have the best luck with new Chinese 12AX7s for noise and microphonics but many Russians reject anything made in China so I have to stock other tubes as well and use them even if they do not perform as well.

[daz]

Thats my problem right now. I love the SED winged C 34's, and i've tried almost every other current 34 and just cannot live with them. theres just a certain tone and dynamic i just love. But i can't buy several quads to stock up if they are truly going out of production because when i get defective tubes they tend to go bad after 10, 20, maybe more hours of use and i can't just play for 3 weeks straight all day. So stocking up isn't an option, i'm just shitoutaluck. That is, IF they are out of production. Tubedepot told me only the 6550's are out. (i THINK he said it was 6550's) So i dunno.

On a very surprising side note and one that gives me some comfort, i found that no el34 made me feel like i could be close to as happy as the SED's, but one tube did....a JJ 6L6 ! Not only do i generally not like JJ's, but i swear thier 6L6 sounds closer to the winged C el34 in my amp than any of the el34's, at least as far as the important things i like about them! I even tried JJ el34L's and no go. Even winged C 6L6 sound mediocre in it. In fact, that really surprised me because i figured it might be the best 6L6 going. In 6L6 based amps maybe it is, but in mine JJ 6L6 beats it easily. They don't make me happy as the SED34, but close enough that i won't have serious withdrawal if they do go extinct. So weird....

[Chuck H]

One important parameter is biasing and drive voltage. There are plenty of EL34's out there. Many are more like 7591's or more like 6550's! The parameters for tube designation for the purposes of sale must be pretty weak. But IMHE most big bottle power tubes can be made to behave similar enough if the bias and drive voltage are adjusted for that particular tube. A critical matter that can't be met by circuit adjustment is OT primary impedance. Old Marshall and Fender ideals lean toward the low side. This makes the way a tube responds to dynamic speaker impedance a more critical "feel" factor. I have pretty good luck designing with primary impedances more typical of the data sheets. That is, higher than most guitar amps. Different tubes seem to balance better in the same amp. But that in itself changes the feel by taking every tube to the lowest common denominator in this respect. Still, biasing different tube types to their ideal is a good place to start. I just replaced some Sovtek EL34WXT's (fat bottles. Strange EL34) with some Sovtek EL34B's. The WXT's were adjusted to 40mA current (which was correct for the Vp with those tubes). When the B's were just plugged into the circuit they were drawing 70mA each!!! Once adjusted the tonal difference wasn't startling at all. More similar than I would have expected considering how different the two tubes seem to be otherwise.

[Leo_Gnardo]

When I had my shop before moving here, we had a large box with padding where all the new-bad tubes went(which were not many actually a few a week) and Tom, the owner of Magic Parts/Ruby Tubes would come pick them up and issue a credit. There was no reason to even bother looking for another source with that sort of no-questions asked customer service. He built his business on good testing of every tube so we used a lot of tubes and had very few failures out of the box.

Indeed, God bless Tom & his crew at Magic Parts, even the ex-employees.

Early 90's I was a big fan and user of Siemens EL34. Whoever was really making them for real, they sounded good and were tough as nails. Magic ran out but I found them at ARS. Everything went well for a couple dozen then one day ARS shipped me a dozen or two EI pointy-tops LABELED as Siemens. Orange label painted on the tube, blue & orange box. Now I know EI have their fans but practically ALL these pretenders were failures. I sent 'em back for credit then a couple weeks later got a call from ARS. From their ACCOUNTANT "There must be something wrong with you because none of our other customers have more than 1/10th of a percent failure rate and you're complaining about a 10%-plus failure rate." I calmly explained to her that the tube ARS was shipping was not an authentic Siemens but this did nothing to settle her ruffled feathers. Maybe ARS has some deals but that experience really put me off. No matter - they refused to fulfill any more orders from me. No great loss.

At this time things went to a very low point. The only EL34 available were those awful Chinese ones that had a steel "splint" spot welded to the plate, to keep it from bending as it heats up. Just rubbish. I had a chat with Tom at Magic & he said he learned Chinese & went to the plant where he offered ideas to improve their products, starting with EL34. The plant manager rebuffed him "We make 300,000 EL34 a year, and sell every one of them. What makes you think we need to improve anything." Shortly after that Marshall started using wafer-base Russian "5881" (6P3) and stopped using EL34. I think the Chinese plant manager "got the message" around that time, and put Tom's suggestions to work. Now we have some pretty darn good EL34BSTR and EL34BHT from China via Magic. You can thank Tom for his perseverance in getting that to happen. Coincidentally "real" Svetlana EL34 started showing up right about then, late 90's.

Daz, if those JJ 6L6 sound right to you, "trust your ears" and stock up. It is your ears you're trying to satisfy and that's the bottom line, innit?

[daz]

Daz, if those JJ 6L6 sound right to you, "trust your ears" and stock up. It is your ears you're trying to satisfy and that's the bottom line, innit?

I don't want to stock up on them, as they are readily available and probably will be for many years. JJ has been like that. Plus while they are the closest i've found, the C's still beat them handily. Besides, i still don't know for sure that the C's are out of production. I only spoke of stocking up if the C's will be gone. I will buy another set, maybe a quad. At my age that may carry me thru to the end anyways.

[Leo_Gnardo]

I don't want to stock up on them, as they are readily available and probably will be for many years. JJ has been like that. Plus while they are the closest i've found, the C's still beat them handily. Besides, i still don't know for sure that the C's are out of production. I only spoke of stocking up if the C's will be gone. I will buy another set, maybe a quad. At my age that may carry me thru to the end anyways.

Daz, I think you can take it as truth, from Stan who for Pete's sakes VISITED the Svetlana plant, that "receiving" tube production has ceased. Regardless of any "blue sky" rumors from tube dealers. Of course dealers are always scrounging around for boxes full of unsold tubes, that's what they do, so there's always hope they'll find more to sell. And I hope I buy the winning lottery ticket, too. And if not me, you.

And we've also seen JJ's quality control go from bad to well, sorta OK, and back again. A couple of years ago I depended on their 5AR4/GZ34. Now I can depend on them to FAIL. Magic told me a couple years ago they got a shipment of 200, and 199 were bad. "JJ has been like that." I'd say get your JJ 6L6's while the gettin's good. The future's uncertain.

Here's to your good health, long life, & not running out of your favorite tubes.

And thanks for the headsup on the tilting tubes phenomenon. Sounds like loose grids to me.

[daz]

Now I can depend on them to FAIL. Magic told me a couple years ago they got a shipment of 200, and 199 were bad. "JJ has been like that." I'd say get your JJ 6L6's while the gettin's good. The future's uncertain.

But the gettin is NOT good from the first sentence above. Gotta be something that will come along thats good. There seems to always be something currently good. Before the SED there was GT EL34LS made at the tesla factory b4 it became JJ spec'd by GT along with penta. Those were what i used after the seimens ran out. I liked them almost as much, maybe as much. Then those went away and the SEDs came along. I tried the current svets which actually sound more like the SEDs than the JJ 6L6, but they sound like a lousy thin sounding version of them w/o as much mid complexity. Maybe like a worn out SED. If they could change them a bit towards the SED sound they'd be good. Cheap too. The JJ 6l6 doesn't so much sound LIKE the SED34 as it just does the important things i like about the SED34 pretty well.

[Leo_Gnardo]

But the gettin is NOT good from the first sentence above.

Seems at JJ one production line goes bad at a time. Couple years ago something went kablooey on the 5AR4 line and the QC dep't (if there is one) said, in Slovak, "When in doubt, ship it out." Mr J.J. himself when confronted with the problem tried to touch his earlobes with his shoulders "who us? QC problem? Nawwww, couldn't happen. Everything we make is FANTASTIC!" And you & I and the rest of us know, that's baloney, any way you slice it.

Meanwhile I've still been having good luck with JJ's 6V6 and EL84. Until those go bad, I'll continue to install them. You seem to be getting along well with their 6L6, so for the moment they're OK. Too bad, nobody rings the bell to let us know when the quality goes to heck.

Remember when JJ got started say 1999-2003 they made ALL their octal base tubes with pins that were too skinny. Totally unacceptable. After a couple years they did get their s#!t together and make them correctly. So they can do it right, when they want to.

I hope for ALL our sakes someone besides Shuguang-China starts to make an acceptable and affordable EL34. Until then, those are what I'll have to use.

[Chuck H]

Does anyone else find it interesting that the JJ 6L6 is the best sounding EL34 going besides the Winged C's!?! I don't have personal experience with this but I trust Daz's word on it. He's picky and even though he's green compared to some, he always lands in a logical and justified place through a long process of trial and error. He DOES know what sounds good. So, if the JJ 6L6 is the next best EL34!?!?!? Why the hell do manufacturers even bother putting designations on the tubes? IMHE the whole bevy of big bottle, roughly 25W tubes should simply be classified "big bottle tube" with the caveat "figure it out for yourself". I'm sure Stan has the toughest time with that. The need to explain every tube he sells! What a pain in the ass. Kudos to him for taking it on. It's somehow comforting that the problem is recognized and being handled by someone. Even if we don't have that luxury in the U.S.

[Randall]

I like JJ's. I've had one bad set that got replaced, but other than that I'm still on the team. And I play in bands.

[Mick Bailey]

Remember when JJ got started say 1999-2003 they made ALL their octal base tubes with pins that were too skinny. Totally unacceptable. After a couple years they did get their s#!t together and make them correctly. So they can do it right, when they want to.

The JJ 6L6 has thinner pins than the Svetlana by .006" - at least the ones I have here are which are current production.

[daz]

I'm not saying that at all. All i'm saying is that it seems to have less deviation from what i like about the WC34 than any of the other 34's i have. And it sounds closer to a el34 than any other 6l6 i've used, but NOT just like one. It's totally subjective. You may hear it differently but to me it simply deviates less from what i like about the WC. I also don't at all think it's better than other current el34....it just is to me, and note that it's very dependent on the particular amp too, not just the particular ear.

Does anyone else find it interesting that the JJ 6L6 is the best sounding EL34 going besides the Winged C's!?! I don't have personal experience with this but I trust Daz's word on it. He's picky and even though he's green compared to some, he always lands in a logical and justified place through a long process of trial and error. He DOES know what sounds good. So, if the JJ 6L6 is the next best EL34!?!?!? Why the hell do manufacturers even bother putting designations on the tubes? IMHE the whole bevy of big bottle, roughly 25W tubes should simply be classified "big bottle tube" with the caveat "figure it out for yourself". I'm sure Stan has the toughest time with that. The need to explain every tube he sells! What a pain in the ass. Kudos to him for taking it on. It's somehow comforting that the problem is recognized and being handled by someone. Even if we don't have that luxury in the U.S.

[drewl]

The JJ 6L6 sounds like an EL34??
What about the other specs, Impedance etc?

If so, that's funny.
I've used plenty of JJ EL34's but not 6L6's, I'm tempted to pick up some to try this for the heck of it.