JJ 6L6GCs... WTF?

[km6xz]

A customer brought back a Hot Rod Deluxe yesterday that I put a pair of JJ 6L6's in at his request only a week ago. Despite an extensive burn in and careful attention to microphones, it came back making a terrible racket. One of the tubes must have a loose element inside, just walking across the hard wood floor sets it off, a light tap with a fingernail sends it into convulsions. I have already given up on JJ EL34 on any amp with higher than 400 volts on the plates because of rapid failure soon follows in too many models.
Reports come in that they sound good but I can't trust them to be reliable.
The most reliable tubes I have are old Soviet era 6п3с-е that are still available in quantity but some people think they do not sound as good. They have a little lower gain but if driven up to the same level they do a good job of generating the harmonics that people are looking for.

[MstrB]

Interesting, back in 2004-5 we were having a lot of problems with Sovtek power tubes. You would have them on the probes and their bias point would change before your eyes. We felt that it was a low quality in the metal used in the plates at the time. We changed to the JJ's and found great results. I have been stuck working on SS mostly lately but am looking to buy more tubes and am happy to learn from you folks. Any suggestions on 7027's?

[g1]

Any suggestions on 7027's?

I think you saw the VT-40 thread (http://music-electronics-forum.com/t25895/) that discussed this, but I'll reiterate. All current production 7027's are re-pinned 6L6's. They are rated for 500V plate, not 600V like "real" old 7027's. Most musical instrument amps that use 7027's do not use the extra pins so 6L6's will work fine.
So unless you need the extra pins it is pointless to use current production 7027's, plus they cost more than the 6L6 versions.
If you want the 600 plate volt rating, you must buy old production 7027's.

[jbltwin1]

By the way, the JJ E34L's are the only ones that I use. I use them exclusively in Music Man amps. 700v. No failures. Also from Euro. Their website is a LITTLE confusing but geez guys, are we going to hold their WEBSITE against them? Man, you guys are tough. I;m more worried about the PRODUCT. There, I have no complaints. Flame on. Mike.

[The Dude]

I had some trouble with my tube vendor a while back. At least 60% of the tubes were bad out of the box and un-useable. I got burned bad because they would not take them back after 30 days and I got stuck with a batch of crap tubes. Since then (yeah, I know, it's ridiculous), I run every tube on the tester when I get them. I've been buying exclusively JJ's because they have had the lowest "defective out of box" rate. I'll use something else if the customer requests, but otherwise they get JJ's. I'm surprised and a bit spooked to hear about this problem. Makes me wonder what the next batch will be like. Oh, .... and I don't use my old vendor any more.

[The Dude]

I go through quite a few tubes. If you consider 2 months ago "old production", I guess nothing useful. I'll put it another way: I've not had problems with JJ's. This makes me think that possibly the OP just got a bad batch. I do have a suggestion, but in the interest of being polite, I'll leave it at that. And,......you're welcome.

[g1]

Dude, I think that was aimed at me and my response regarding 7027's:

Most musical instrument amps that use 7027's do not use the extra pins so 6L6's will work fine.
So unless you need the extra pins it is pointless to use current production 7027's, plus they cost more than the 6L6 versions.
If you want the 600 plate volt rating, you must buy old production 7027's.

MstrB: My point is that the current production 7027's are actual 6L6 tubes repinned.
So if you read up on what are considered good current production 6L6's, the same info should apply to current production 7027's. For real 7027's, you must buy vintage old tubes.

[The Dude]

I thought of this thread today. Opened up a Marshall TSL100 for a customer. He told me he had just replaced all of the tubes. I ran them on the tester anyway because of recent problems with bad out of the box tubes. All 4 preamp tubes were bad Mesa tubes, supposedly brand new. I was starting to think my tester was bad, so I stuck in one of my JJ's out of stock and it tested just fine. I shot the guy an email to see if he still has the originals to save him some money. Waiting to hear from him. The amp had the infamous shorted C46 and one of the screen resistors was completely missing. I'm not sure how it could have disappeared. I looked under every circuit board, shook the amp, etc., and couldn't find it anywhere. Anyway, the short of it is that this guy not only bought new tubes that he didn't need, but the new tubes were crap!

[Leo_Gnardo]

Opened up a Marshall TSL100 for a customer. The amp had the infamous shorted C46 and one of the screen resistors was completely missing. I'm not sure how it could have disappeared. I looked under every circuit board, shook the amp, etc., and couldn't find it anywhere.

Geeze those TSL DSL 2000 series Marshalls are a headache! I'm sure you know about the dreaded conductive-circuit-board problem. Eats output tubes if not corrected. That screen resistor might have just walked off the job in disgust. Had one 2000 that melted the glass on its EL34's.

New customer just dropped one off, here we go! Break out the Dremel, and the aspirin. The 2000's can be fixed, with surgery.

[Bruce / Mission Amps]

I go through quite a few tubes. If you consider 2 months ago "old production", I guess nothing useful. I'll put it another way: I've not had problems with JJ's. This makes me think that possibly the OP just got a bad batch. I do have a suggestion, but in the interest of being polite, I'll leave it at that. And,......you're welcome.

I bought a couple dozen Sovetk 6L6WXTs... used most of them up now and have not had a bad one.
On a whim while getting some speakers, I ordered another quad of JJ6L6GCs from CE Dist and tried them yesterday in an amp I just finished.
Same problems.... noisy mechanical crap, NO MORE JJ 6L6s for me. They are just junk now.

[bob p]

Are you using CED as your supplier for the Sovtek ^L^WXT, or are you getting them elsewhere?

Trying to determine if this could be attributable to poor handling of merchandise by the supplier.

[bob p]

BTW, that was supposed to be "6L6WXT" in the above post.

Are your problems confined to the 6L6, or are you also seeing the same problems in the JJ 6550, KT-88, KT77, etc.?

[Leo_Gnardo]

I dunno what's the problem with JJ 6L6's lately but thanks for the heads up. They had been recommended as a sub for 7027 but looks like that idea has come & gone. I was going to order some but now not.

A couple weeks ago someone mentioned CE/Antique is no longer guaranteeing their tubes for microphonics. Maybe they know they bought a pile of piss from JJ and dont have the ba!!s to send it back to Slovakia with a note where to shove it. And CE/Antique has to try to sell crapulent JJ's without any guarantee except the filament will light up, maybe.

A few years ago I started having problems with JJ 5AR4/GZ34 sourced from Ruby. When I asked at Ruby they told me their latest package from Slovakia had 199 BAD and one good. Ruby's boss man sent 'em back and demanded a refund, also a boot-up-the-arse note to JJ's boss. That's the way to handle it.

It really makes me wonder if JJ sends their better testing tubes to their friend/relative at Eurotubes, and sends their shite to everyone else. Or if their overall QC is really as dodgy as it seems to be. Damn shame. They can make a good tube when they want to. So far 6V6 and EL84 are hanging in there, seldom a problem.

[tubeswell]

I use Russkie 6P3Se in all my 6L6-based amps now. I have never fully trusted JJ 6L6GC (even tho' I have no problems with countless of their 6V6S).

[Leo_Gnardo]

I use Russkie 6P3Se in all my 6L6-based amps now.

Are these the wafer-base tubes Sovtek started to market as 5881 @ early 90's? If so, yes they're pretty tough. Have you found a safe upper limit for plate & G2 voltage? I'm trying to find something that will sub for 7027A in old Ampeg V2, V4, VT40, B18 & similar amps with @ 550V on both.

Thanks, LG.