JJ EL84 failure

[brendo613]

Hey all. Had a JJ EL84 fail on me - wanted to discuss what happened here. Pin 6 appears to be touching pin 7 (the plate). Pin 6 is an "internal connection," multiple online sources tell me. The amp had a hot smell when running, but so do many amps that have dusty tubes ... oops . The tube has a darkened hue to it - check it out:

I'm thinking that, internally, 6 & 7 touched but weren't supposed to. What are your guys' thoughts?

[Jazz P Bass]

Now you got me wondering.
I never took notice of that i.c. designation on the tube datasheet.
So I pulled out an EL84.
Pin 6 appears to be attached to the mica insulating spacer.
So that does not look as if it would take out a tube, if pin 7 (plate) "touched" it.
It appears that all of the pin connections pass through one or the other of the mica spacers.

[Enzo]

IC for internal connection on a tube means you cannot use the pin for some other purpose. I really doubt that pin got bent inside the tube. To meet the EL84 spec, certain pins must have certain functions, and the innards have to perform in certain ways. The remaining pins are not necesarily assigned the same way in all cases. The Chinese Bugera EL84s I am looking at here use two of those pins as extra supports for the lower mica wafer, but appear to have no electrical connection to other pins. Pin 8 seems to be a wire that sticks striaght up and does nothing.


SOme examples:
Pin 1 on a 6L6GC is not connected to anything, so it becomes a handy point to solder the other end of a grid resistor to pin 5. But on the original metal 6L6 - plain 6L6, no extra letters - pin 1 was a shield connection, basically the metal shell. You cannot then solder the grid resistor to it. Pin 1 on a 6550 is also a shield pin, the metal base. And on both those, pin 6 is not connected, so is free. In fact those tubes usually don;t even HAVE a pin 6.

Look at your other EL84s. Does your amp use more than one of them? If they are also JJs, are their pins 6 and 7 joined?

Look at the circuit of your amp, whatever it is. Is there anything connected to pin 6 of the socket? If there is not, then it doesn;t really matter what the internals of the tube do to that pin.


Your tube failed, but I don;t think that is where it failed inside the tube. More likely a grid wireform broke free or broke off and shorted two elements together that way. That is just an opinion.

[brendo613]

Right, not really sure what happened on this tube then :| I should mention - this tube used to flash upon startup. I then went on to learn that this was "normal." Not sure where I learned that, nor if that is so. Either way, take a look & let's add this to the bad-tube equation, hehe

[ttung51]

JJ Tubes Suck! I had nothing but problems with their tubes. That Guy Bob will blame your amp if the tubes fail. He ripped me off. To him the customer is allways wrong.

[brendo613]

That makes for an effective company policy. I'm battling a clutch supplier, on the grounds that they meet their own warranty terms. D'oh.

I don't run a business, but if I did ...

[imaradiostar]

JJ Tubes Suck! I had nothing but problems with their tubes. That Guy Bob will blame your amp if the tubes fail. He ripped me off. To him the customer is allways wrong.

There are many many successful JJ tube users out there. Do you have a large statistical sampling to show that they're problematic? Which tube has given you trouble? I have not personally had any problems with them and so far have been able to run some JJ tubes far in excess of their "rated" capacity without failure.

jamie

[überfuzz]

I tend to avoid JJ tubes, as they and I have a history. I bought 6 ECC83 some years ago from a local supplier. 2 was bad from shelf and 2 failed me in a couple of weeks. The local supplier didn't fuss, just gave me new ones. I think I vent there 3 or 4 times before I had 6 working tubes. I know, probably just a bad batch. I just wonder why the bad tubes were ever shipped from the factory.

[Enzo]

They were shipped because tubes are not tested in the manufacturing process. They are made in a process known to provide working parts. To then socket each one of tens of thousands of tubes, warm them up in a measuring circuit and burn them in would add a lot to the cost. To you an extra $2-3 might be OK, but when Peavey or Fender or MArshall buys 10,000 of them, they just get them bulb and deal with the small percentage of bad ones. Most tube sellers offer burrned-in tubes for a slightly higher price.

[Steve Conner]

The interwebs is a big place with lots of people in it.

Unhappy customers are more vocal than satisfied ones.

Even the best manufacturer will have an occasional dud delivered into a customer's hands. It is not economical to 100% test everything. Even if he follows genuine Six Sigma, he could have 3.4 lemons per million units sold, and how long do you think it takes Apple to shift a million i-thingoes?


Therefore, you can always find clusters of people complaining of a terrible experience with Product X, even if Product X is actually pretty good.

See appledefects.com for an example, the "Fizzy sound in Vox Night Train" thread for another.

Now, when you google the name of Product Y and the whole top page of search results consists of "Help, Product Y is broken", then you know you have a problem.

[jmaf]

JJ tubes have had bad lots out there.

I had this guy here write me about a Peavey that was popping after he replaced Ruby with JJ. I asked him to flick the power tubes. He said sure enough it popped.... It was the short pin JJ...

One thing I learned: tube selection companies buy tens of thousands, then select the best for their use and I have a feeling they dump the rest on the internet.

I bought expensive SED 6L6 tubes here 3 years ago, they started arcing within a week or so.... I think these are rejects from major tube selection companies, they end up here in Latin America and elsewhere.... I know for a fact that refurbished notebook computers and computer parts end up here, why not tubes....

[hasserl]

JJ tubes have had bad lots out there.

I had this guy here write me about a Peavey that was popping after he replaced Ruby with JJ. I asked him to flick the power tubes. He said sure enough it popped.... It was the short pin JJ...

One thing I learned: tube selection companies buy tens of thousands, then select the best for their use and I have a feeling they dump the rest on the internet.

I bought expensive SED 6L6 tubes here 3 years ago, they started arcing within a week or so.... I think these are rejects from major tube selection companies, they end up here in Latin America and elsewhere.... I know for a fact that refurbished notebook computers and computer parts end up here, why not tubes....

I was just going to mention this before reading your post. To the guys that have had bad experiences with certain tubes, where do they think their supplier got the tubes from? Could it be he bought some seconds or rejects from a larger tube dealer or from one of the larger OEM's that sorted them out? Maybe? If you bought from Eurotubes, that shouldn't be the case, as they are the importer to the states I believe. But if you bought from someone else, think about it, what is his source?

[Rhodesplyr]

I bought expensive SED 6L6 tubes here 3 years ago, they started arcing within a week or so.... I think these are rejects from major tube selection companies, they end up here in Latin America and elsewhere.... I know for a fact that refurbished notebook computers and computer parts end up here, why not tubes....

I liked the EL34 variant, the E34LS that Groove Tubes had made in Slovakia, but there was a place selling them for about half what you'd pay for ones with the Groove Tubes label on them, so I bought some. I had major problems with them--things like the screen grid connection not being properly welded inside the tube, etc... So, yes, I now only buy new production tubes from dealers who exercise some level of quality control. I may pay a bit more and pass that cost on to clients, but it means there's much less chance of them having a serious tube failure during a performance.

That output tube is about the only Groove Tubes-labeled tube I've ever liked.

[jmaf]

I was just going to mention this before reading your post. To the guys that have had bad experiences with certain tubes, where do they think their supplier got the tubes from? Could it be he bought some seconds or rejects from a larger tube dealer or from one of the larger OEM's that sorted them out? Maybe? If you bought from Eurotubes, that shouldn't be the case, as they are the importer to the states I believe. But if you bought from someone else, think about it, what is his source?

Exactly.

A few years back JJ was still riding on Tesla's fame and they were still more expensive than Sovtek, Svetlana, etc... All of a sudden JJ's are on sale everywhere at 10 to 20% less than Sovtek....

I thought either Jan Jorgo quadrupled his prodution, or a large lot of JJ's had been rejected off some selection system and dumped into the market. I am willing to bet on the latter from what I've heard lately.

Having said that, personally, in my experience I haven't had more issues with JJ to be honest, I like them in fact. But it's true that there's been issues with them lately. Selecting a tube provider who is trustworthy is crucial nowadays.

[tubeswell]

I love the JJ6V6S. I'm not so hot about their 6L6GC. Some of their pre-amp tubes I've tried also have worked without complaint. I buy them from a local supplier who burns 'em in, so he only sends me good ones.