Inside a JJ 6L6GC.

[Scott S]

Forum member Stuco (aka Patrick) was kind enough to send me the no-longer-serviceable JJ 6L6GC last seen in this thread. I've been longing to open up and study one of these bad boys, partly since I admire the robust construction of these tubes, and partly because I just enjoy looking at the insides of tubes.

Here it is. If you zoom in, the crack that killed this tube is close to the base, between my thumb and middle finger.


Finishing the job.


Next to one of my beloved metal 6L6's. These were rated at 19W max plate dissipation, while the JJ is rated at 30W.


Here I've trimmed off the getter haloes and grid cooling fin, so I can remove the top mica.


- Scott

[EdMax]

To bad you could not have gotten the glass off with a cutter of some type. It would have been neat to diagnose why they are so venerable to rattling so bad.
I have had a lot of problems with that in combo amps, and o-rings do not correct the issue. Its a shame, they are such a great tube..

[Scott S]

Took me a while to get a decent shot down into the tube. You can see a goldish hue from the gold-plated grid wire.


A disencased 6L6G decided to join on the left. I absolutely love the ST-shaped tubes, but you can see that there was a lot of wasted space inside the bottle.


Here I've cracked open the welding on one end, to show the striptease view.



I measured the metal 6L6's plate at 0.007" thick. The JJ's plate is twice as thick at 0.014"! Check out those grid support rods -- they measure right around 0.049" in diameter! The bottle's glass is about 0.039" (1 mm) thick -- I measured it at the edge to get a more accurate reading.

Hope you guys dig it. I can take more pictures if there is interest.

- Scott

[Scott S]

Originally Posted by EdMax

To bad you could not have gotten the glass off with a cutter of some type. It would have been neat to diagnose why they are so venerable to rattling so bad.
I have had a lot of problems with that in combo amps, and o-rings do not correct the issue. Its a shame, they are such a great tube..

Just looking at them, you'd think they'd be pretty impervious to rattle -- the micas fit the glass pretty snugly in this tube, and it took some gentle persuasion to get the top of the bottle off. Once I took the top mica off, I noticed the cathode and grid rods were a little loose in the bottom mica, so perhaps that's where the problem lies.

- Scott

[EdMax]

Originally Posted by Scott S

Just looking at them, you'd think they'd be pretty impervious to rattle -- the micas fit the glass pretty snugly in this tube, and it took some gentle persuasion to get the top of the bottle off. Once I took the top mica off, I noticed the cathode and grid rods were a little loose in the bottom mica, so perhaps that's where the problem lies.

- Scott

You could be right!

Maybe its transmitting the problem to the glass.

I have resorted to replacing everything with =C= winged C tubes because they seem to be better supported.

One thing for sure, some of the JJ's I have never rattled, others more recently have been bad right out of the box.
Must just be a QC thing or worn out mica die.

[Stuco]

This was (almost) a brand new tube. It was only used for a few days. As to if it was damaged in transit or installation or drunkeness I'm not sure. My guess is that it had a very small crack where the glass connects and it spread from there with a little pressure was applied when installing but who knows. I have since gotten another matched set so I have this broken one's partner as a backup.

[Cleeve]

As a safety measure, read about Thorium and how to wash it from your hands. It's an Alpha Particle emitter that is or was often used on the cathodes and/or heaters in thermionic devices. You may already know this, and I'm not sure if Thorium is still used.
It's the same radioactive stuff that is on Coleman lantern mantles for some reason.

[Scott S]

Originally Posted by Cleeve

As a safety measure, read about Thorium and how to wash it from your hands. It's an Alpha Particle emitter that is or was often used on the cathodes and/or heaters in thermionic devices. You may already know this, and I'm not sure if Thorium is still used.
It's the same radioactive stuff that is on Coleman lantern mantles for some reason.

That's a good point. As an indestructible young guy , I probably don't think enough about the barium, strontium, and other rare earth elements I'm encountering. According to John Harper's page, thorium was used mainly on older directly-heated tubes.

- Scott

[Cleeve]

You're probably fine as long as you dont pull out the heater element and snort it!
It is interesting to open these things.. I wonder how much PCB I've been exposed to by opening capacitors to see how long the coil of aluminum is.

[eggman]

Howdy,

Informative thread. Thanks for posting, ScottS.

Eggman

[Jelle]

Very nice; thanks for posting

[JohnnyCrash]

Originally Posted by EdMax

You could be right!

Maybe its transmitting the problem to the glass.

I have resorted to replacing everything with =C= winged C tubes because they seem to be better supported.

One thing for sure, some of the JJ's I have never rattled, others more recently have been bad right out of the box.
Must just be a QC thing or worn out mica die.

I LOVE Winged C 6L6's!

Every JJ I have/use seems to be pretty overbuilt compared to other brands. I dig em for 6V6's, but never took to em for 6L6's. I also have a pair of JJ EL34's that seem so-so.

[LoveBandit]

Just as a data point: I love JJ Tubes also but I have had a few of them rattle also (this is when new) and it really bugged me. LB.

[EdMax]

Originally Posted by LoveBandit

Just as a data point: I love JJ Tubes also but I have had a few of them rattle also (this is when new) and it really bugged me. LB.

Same Here, This is extremely common of their 6L6GC's & their 6V6S tubes.

I buy a heck of a lot of tubes, and it seems to run about 75% rattle right out of the box (in combo amps).
I have a hard time finding that acceptable, but Damn they are fine sounding tubes otherwise.