JJ E34L Tubes... Bad batch?... Anyone have issues recently?

[gf3364]

Hi all,

Anyone else have issues with JJ E34L's recently?

Recently completed a new build(not a kit) that came with JJs. Within 6-7 minutes of powering up for the first time, after checking/setting the bias, two hot plated / red plated, kicked the HT Fuse, and were toast.

Checked the tube sockets(OKAY), and voltages(OKAY) then, popped in a set of GT34LS that I have in another amp. Checked the voltages again, checked/set the bias. Everything totally fine.

Ordered another set of JJs. Ran the GTs for a week while waiting for the JJs to arrive. New JJs show up, back to square one, put the JJs in, check voltages and check/set bias. All good and 2 minutes later one pops almost like a light bulb burning out, the HT Fuse kicks again, and of course, another tube toast.

So, I take my two known okay JJs from set one, and two known okay JJs from set two, and make up a quad. Back in business.

Over the next couple weeks, trying some different "tweaks" and mods so the amp doesn't get a whole lot of use other than testing the changes made, nor does it get pushed very hard.

This past weekend, on Sunday, I wired up a cascade to try it out. Ran the amp for about 5-10 minutes, and two tubes hot plating / red plating again and the HT Fuse blew again!

Checked all the tube sockets(OKAY), completely checked ALL the leads/wiring in the amp. Changed the screen grid resistor wiring after reading a post about possible oscillation causing red plating. So, switched the screen grid wiring from a single 1.5k across V4/V5 Pin 5 and V6/V7 Pin 5 to one 1.5k at each Pin 5, then each pair joined.

Tubes still hot plating / red plating. And of course, the hot plating / red plating follows the tubes so, I am quite certain it's the tubes.

The other strange thing;
When checking B+ voltages prior to putting the tubes in, the B+ voltage was at 499v. The voltage readings at pin 5 was -55v(with the bias pot backed off to the limit) which is as cold a starting point as I could get. Once tubes were installed, I checked all the voltages again and proceeded to bias to 35ma which is the calculated value. Then rechecked all the voltages, to find the hottest tube, and fine tune the bias from there.

With the JJs in, V4 B+ = 486, V5 B+ = 483, V6 B+ = 484, V7 B+ = 484 so, I biased based on V4 being the hottest tube.

With the GTs in the amp, all B+ voltages are bang on 499 and the bias is exactly the same on each tube.

One thing I can say for the GTs... albeit a bit harsh sounding, they are tough as nails! This set is like my bench set that have been in many amps to test with, and when not on the bench spend their time in a modded X100B I have that gets run hard.

Are the JJs just garbage lately? Bad quality control? Bad production run? ????

I've heard good things about JJs E34Ls, have had good luck and results from their preamp tubes in other amps, and from what everyone describes, the sound is what I'm after vs. what others describe EHs or Winged Cs to be like.

I am really reluctant to get another set. At $100.00 a set including shipping, taxes, etc. this is already expensive for an amp that barely has any hours on it and I don't feel like blowing another set, or two, or more!

Comments, experiences, suggestions welcome.

[SandovalPDV]

I have no experience with el34 from JJ but I have used their 12ax7's and el84's with no tube failures at all and I have alot of time on these tubes. They still sound great I've got about 400 hrs a Mesa dc-2 and about 100 on a 60's Vox ac30. Where are you getting your tubes from? Eurotube.com has a quad of el34 for $54 not including shipping and taxes if you live in Oregon. I know he tests his tubes before he ships them. I've ordered from him a few times with no problems at all. I guess it is possible to get a bad set of tubes. They could have been damaged in shipment. I will be ordering a set for my Super Lead. I will report on them when get around to ordering them. George supplies them with his kits if they were a bad tube I don't think he would use them.

[AustinTx]

Yes......I have burned up 4 Quads of KT66's since Feb 1rst... My amp tech has been in contact with the main JJ distributor and others are having problems right now. JJ outputs are normally pretty bulletproof. Total Bummer, I had to temporarily switch to Gold Lions.

[axeman]

I've heard good things about JJs E34Ls, have had good luck and results from their preamp tubes in other amps, and from what everyone describes, the sound is what I'm after vs. what others describe EHs or Winged Cs to be like.

I am really reluctant to get another set. At $100.00 a set including shipping, taxes, etc. this is already expensive for an amp that barely has any hours on it and I don't feel like blowing another set, or two, or more!

Comments, experiences, suggestions welcome.

JJ tube work and sound great. Check your grid stoppers/blockers and make sure they are of correct value. I've sold plenty of E34L's and KT88's this year and a bunch of them last year and I have not had one tube come back yet, not even last year. JJ tubes work well and you should give them a second chance. Try the ones that Gorge sales. He haves a maxi matcher and can sale a great matched quads. So I hear.


Axeman

[gf3364]

Hey SandovalPDV,

This was my first time the JJ E34Ls. I made the choice because of what I heard and they sounded like what I was after. I too had used the 12ax7s many times and liked them.

I got the tubes from reputable places. I don't want to name names because it's definitely not their fault and I don't want to come across as pointing fingers ya know?!

I've had the Groove Tubes in the amp since the first post... no drift, no issues! Have run the amp fairly hard with and without an attenuator.

I ordered another set so, I'll definitely be "reporting" on what happens.

Thanks man!

I have no experience with el34 from JJ but I have used their 12ax7's and el84's with no tube failures at all and I have alot of time on these tubes. They still sound great I've got about 400 hrs a Mesa dc-2 and about 100 on a 60's Vox ac30. Where are you getting your tubes from? Eurotube.com has a quad of el34 for $54 not including shipping and taxes if you live in Oregon. I know he tests his tubes before he ships them. I've ordered from him a few times with no problems at all. I guess it is possible to get a bad set of tubes. They could have been damaged in shipment. I will be ordering a set for my Super Lead. I will report on them when get around to ordering them. George supplies them with his kits if they were a bad tube I don't think he would use them.

[gf3364]

Yes......I have burned up 4 Quads of KT66's since Feb 1rst... My amp tech has been in contact with the main JJ distributor and others are having problems right now. JJ outputs are normally pretty bulletproof. Total Bummer, I had to temporarily switch to Gold Lions.

Ouch!

Well, I'm currently waiting on set #3 so we'll see. I'm up north of the 49th so no matter how I look at it, it's close to $100 a set from the US and most places here are either more or don't have JJs. Starting to hurt the budget!

So, sounds like something may be up. I'll be interested to hear what your tech finds out re: problems of any kind.

Thanks for the input.

[gf3364]

I've heard good things about JJs E34Ls, have had good luck and results from their preamp tubes in other amps, and from what everyone describes, the sound is what I'm after vs. what others describe EHs or Winged Cs to be like.

I am really reluctant to get another set. At $100.00 a set including shipping, taxes, etc. this is already expensive for an amp that barely has any hours on it and I don't feel like blowing another set, or two, or more!

Comments, experiences, suggestions welcome.

JJ tube work and sound great. Check your grid stoppers/blockers and make sure they are of correct value. I've sold plenty of E34L's and KT88's this year and a bunch of them last year and I have not had one tube come back yet, not even last year. JJ tubes work will and you should give them a second chance. Try the ones that Gorge sales. He haves a maxi matcher and can sale a great matched quads. So I hear.


Axeman

Hey Axeman,

Yeah, checked, checked again, rechecked the whole amp and everything is fine. As noted in another response, have had my trusty bench set of Groove Tubes in the amp since the first post, and everything is fine!

Set #3 on the way.

Thank you as well!

[Big Mike]

Kooky. Any luck?
Actually those GT's ARE JJ's with some extra heat dissapating 'wings' for higher voltage tolerance. Or so I read.


I've been using the E34L's in my cathode biased amp. Other than that the amp uses tubes hard, I've had no issues as of late with JJ Power. Maybe try a set of their KT77's which I also like.

[RussB]

I have read of others experiencing troubles with the EL-34L JJ's


Where are you buying your tubes from?

[Big Mike]

now that i think about it, I may be using the GT version in my amp...I can't remember. That's a slightly different tube.

[nsabino70]

I had a while back a JJE34L redpalte 2 mins into the amp. Got a pair in exchange, no problems since.

Nelson

[Kevin]

Well, I'm currently waiting on set #3 so we'll see. I'm up north of the 49th so no matter how I look at it, it's close to $100 a set from the US and most places here are either more or don't have JJs. Starting to hurt the budget!

Where are you getting your tubes? thetubestore.com is in Ontario, and should make more sense than bringing them over the border.

I have always avoided JJs - along with pretty much all other current production. A set of RFTs might cost you a bit more, but will last a lot longer, and sound a lot better.

[big_teee]

I just had a fairly new JJ KT77 tube fail.
It blew and took out the B+ Fuse, in my 2204 Build.
I called TubeDepot where I bought the tubes, and they said that Not Un-Common for a JJ.
Terry

[johniss0001]

I know i may be a tad late here on replying about jjs everytime i have had jj e34ls there has been a problem no disrespect meant to the people who sold them to me. 7 years ago I bought a quad of e34ls from george and they died after less than 5hrs started humming so was no use. Last quad i had of jj e34ls came in a 1968 laney supergroup they were biased waaaay too hot i.e. 58mV on a 600VDC amp!!!! Not only were they biased way too hot tried the valves in a diff amp as i use these as test valves but they have become microphonic and hum in my laney.

Only valve I haven't had any trouble with is the chinese i have them in all my vintage amps and i install them in clients amps and not had a single complaint or failure.

[sixpakldp]

I've had problems with JJ EL34's in the past. A long time ago, prior to owning my metro I had a JCM 2000 with a quad of JJ's.

That amp was unreliable which is why I built a metro in the first place, however compounding that issue was a bad quad of JJ's. The amp was constantly at my local music shop between gigs for problems and one of those instances was due to a bad set of JJ's that appeared to have small metallic dust floating around inside the tube. If you flicked the tube ever so slightly, it would cut out due o the particulates floating around int he tube. Later when I got my metro I bought a set of spares which were JJ's, after close inspection I found the same metallic dust floating around. I had two brand new tubes that would red plate, but if I swapped them out for some Svetlana's I had lying around the problem would go away.

I've been Tung Sol EL34B's for a few years with EH 12AX7's for a few years now and I love them. I'm due for some new glass and tempted to try the JJ 6CA7's, but after a few bad experience with JJ's I might just stick with the Tung Sol's.