50% failure rate

[Tonegeek]

On my last 2 consecutive orders, I have gotten 1 bad tube with each matched pair of JJ EL-34's. So, 4 tubes ordered, 2 bad. The tubes were ordered to replace a matched set of JJ's, 1 of which went microphonic after 14 months of use. Can't blame AES at all for this as the tubes were probably working when they left their site. All the tubes worked at least for one day. The first one lasted a week and the second one lasted for one day. The next day it sounded like it shorted directly out. I thoroughly tested my amp for loose sockets etc. and even swapped the tubes in another socket and even another amp to confirm it was indeed the tube. The way I identified the bad tube initially was I put the standby switch in the run position, then turned the AC switch on while I monitored the bias. As the tubes warmed up the current draw shot up to about 88ma before I turned the amp off. It is unlikely I have issues with my bias circuit because my spare tubes work just fine. Also the problem follows the tube to whatever socket I put it in. Of course if there is anything I am overlooking, I would love someone to chime in. I really think it is the tubes. I sure would like to know exactly what goes wrong physically with tubes when they fail this way. I assume there is either parts too close together that touch or arc when powered up, or bad connections internally that open up.

AES is good about replacement and they even credit you for your shipping, but it seems JJ has a QC issue.

[Structo]

Yeah I don't know if it is a dealer problems with QC of their tubes or not, or if it is just current production tubes that are the issue.

BTW, Bob at www.Eurotubes.com sells only JJ's at a good price and I have never gotten a bad JJ tube from him.

[Tonegeek]

Yeah I don't know if it is a dealer problems with QC of their tubes or not, or if it is just current production tubes that are the issue.

BTW, Bob at www.Eurotubes.com sells only JJ's at a good price and I have never gotten a bad JJ tube from him.

Yea I have heard good things about Eurotubes. I will give him a try. I was also thinking about trying the JJ cap cans. Anybody tried them?

[skyboltone]

I've had the same luck with Sovtek lately. %50.

[Sonny ReVerb]

I've used JJ's cap cans in two amps: a 50x50 uF in a p1eX from AX84 and a 32x32 uF in an 18Watt. Haven't had any problems with either of them. I got them from Angela's. They have some good prices on them.

[Structo]

If you go to Eurotubes Bob has some info on the JJ factory and their R&D programs.
They seem to be one of the few companies that really is trying to improve their tube design and reliability.
But at 50% failure rate, they need to work harder, yes?

[CaseyJones]

It's pretty simple... capacitor technology has continued to improve so you can buy capacitors handrolled in a mud hut and they'll perform as expected. Tube technology unfortunately is obsolete so it's a wonder that new tubes work at all.

JJ has been pretty good about improving their product and addressing quality issues ASAP. Their EL34s are inexpensive compared to NOS so my suggestion would be to buy them in quartets, go for a good hard burn-in then shrug your shoulders and replace any duds.

I guess if you own a 100 watt Marshall you'll have to buy a couple quartets and keep yer fingers crossed.

[Lonely Raven]

If you go to Eurotubes Bob has some info on the JJ factory and their R&D programs.
They seem to be one of the few companies that really is trying to improve their tube design and reliability.
But at 50% failure rate, they need to work harder, yes?

I think Bob is related in some way to the people who own or work at the JJ factory (through marrage?)...I forget what the story is, but I heard it years ago. Could just be internet lore, but I was told that's how he became (the original?) importer of JJ tubes.

I've been buying from Bob since he first put up a web page. I've never, ever received a bad tube from him. He's a very nice guy to boot.

[Structo]

I think what it is is that he has a relative that lives in the Chzech Republic but no direct relation to JJ.
It's all on his website.

After spending a few days with relatives just outside of Prague in the Czech Republic my cousin Jiri Pletka found and set up a meeting with two different tube manufacturing companies. KR Enterprise and JJ Electronic.

http://www.eurotubes.com/euro-b.htm

[gearhead]

A small number of new tube sellers burn in (most of) their power tubes for 24 hours. Eliminates infant mortality and cuts down on mismatching if they drift in the first few hours.

One of them is Lord Valve, whom I've done business with. Another is Boi Audioworks, whom I haven't (but considered).

[Nigel Tufnel]

A small number of new tube sellers burn in (most of) their power tubes for 24 hours. Eliminates infant mortality and cuts down on mismatching if they drift in the first few hours.

One of them is Lord Valve, whom I've done business with. Another is Boi Audioworks, whom I haven't (but considered).

I can fully recommend Lord Valve, if he carries the tube you want (he only carries the stuff that he deems worthy) get it from him. There's several good tube dealers out there that you can find mentioned plenty if you search a few forums but LV is the only one that I've never had a duff tube from. He really puts tubes through the ringer before he lets them go.

[BluzMike]

On my last 2 consecutive orders, I have gotten 1 bad tube with each matched pair of JJ EL-34's. So, 4 tubes ordered, 2 bad. The tubes were ordered to replace a matched set of JJ's, 1 of which went microphonic after 14 months of use. Can't blame AES at all for this as the tubes were probably working when they left their site. All the tubes worked at least for one day. The first one lasted a week and the second one lasted for one day. The next day it sounded like it shorted directly out. I thoroughly tested my amp for loose sockets etc. and even swapped the tubes in another socket and even another amp to confirm it was indeed the tube. The way I identified the bad tube initially was I put the standby switch in the run position, then turned the AC switch on while I monitored the bias. As the tubes warmed up the current draw shot up to about 88ma before I turned the amp off. It is unlikely I have issues with my bias circuit because my spare tubes work just fine. Also the problem follows the tube to whatever socket I put it in. Of course if there is anything I am overlooking, I would love someone to chime in. I really think it is the tubes. I sure would like to know exactly what goes wrong physically with tubes when they fail this way. I assume there is either parts too close together that touch or arc when powered up, or bad connections internally that open up.

AES is good about replacement and they even credit you for your shipping, but it seems JJ has a QC issue.

Why did you perform a cold start for measuring the bias behavior? Skipping the warm-up is always hard on tubes. Is your stand-by wired so that it just turns on the HT, or does it also work on the bias supply? If finding late plexi/early metal panel Marshalls, I immedeately chnge that to the standard wiring of having all but the high voltage supply active in stand-by mode.

In what amp with what plate voltage and what bias setting do you run the JJs? In my experience, all JJs are very well built mechanically, and even the factory matching is reliable enough. You do not want too close a match anyway for a great crunch tone with good harmonics .

Are those the standard EL34s (25W dissipation) or the high-grade E34Ls (30W dissipation), which should be biased differently? I have used the E34Ls even in plexi Laneys, which run 560VDC to 600VDC on the plates and the screens (!!!) without problems. You probably would not try this with any other current production EL34.

[dartanion]

New Sensor has started doing 24 hr. burn in on all the premium matched tubes. So far their failure rate has decreased quite a bit. SED does burn in now as well, but may only be on their cryo tubes.