where to get a cap/sheild for a 6j7

[jeeptechfred]

I am wondering if anyone knows a source for the metel cap/sheild that snaps to the top of a 6j7 type tube (has grid connection on top). Im am building an amp using this tube and I would like to track one down. I can't seem to find a source. Nothing I can see on ebay or on the rest of the net.
Thanks,
Fred

[Phil_S]

eBay, example: http://www.ebay.com/itm/Ten-Pieces-Whit ... 485276794f
The search is for "top cap" in vintage electronics.

[ampfab]

I think he's looking for a metal "shield" like in his photo.
I have not been able to locate one also.

[wyatt]

He's not looking for the grid "cap," those are common enough.

He's looking for the shield that goes OVER the grid cap. So, the grid cap on on the grid pin and then this shield slides over it all. With the grid exposed outside the chassis, requiring a relatively long grid wire, the radio/hi-fi manufacturers used to put a shield over top of the grid connection. I can't imagine it too effective, because I don't think it was connected to ground.

To the OP, I can't say I've seen any shields, we are talking about an optional part made for tubes that became obsolete 65 years ago (by the 6SJ7).

I would use coax to run the grid lead out of the chassis and just settle for a relatively fashionable grid cap. Like so (note the shielf coming off the chassis as well)....
[img2121]http://www.preservationsound.com/wp-con ... detail.jpg[/img]

Stylish grid cap ('40's NOS from Leeds Radio)?
[img:445:177]http://www.leedsradio.com/images-socket ... e-caps.jpg[/img]

[ampfab]

check this link: http://www.leedsradio.com/parts-sockets.html
they list a 6j7 metal grid cap and have a photo.

[Phil_S]

Sorry for not reading carefully. I have a couple of 6J7's complete, but am not willing to part them out. Here are some pictures of the thing you are seeking. You should be able to fashion them from some coax and a bit of sheet metal.

I know this is off the wall, but look at the inserts one your cooking stove knobs. The little spring thingies inside the knob that fit over and grip the post may be adaptable and can be bought from an appliance parts dealer. You just need one with a large shaft size. Maybe I have the wrong appliance...maybe your washer or dryer?

[Phil_S]

Here is the terminal http://www.ebay.com/itm/2pc-NEW-black-b ... 2c6cbbb37f to which you can solder your own coax.

[wyatt]

check this link: http://www.leedsradio.com/parts-sockets.html
they list a 6j7 metal grid cap and have a photo.

That's the grid CAP.

He wants the shield that goes OVER the cap.

[jeeptechfred]

Thanks for the replies. I saw all the ceramic stuff, like said I am hoping to find the totaly obsolete sheild (-: . The metal exterior of the tube is grounded so I think it possible that the cap would make connection to it. I have made metal sheilds like shown in the picture and that is not off the table at all but was hoping to track one down or maybe make one. A 1/2 or 3/4" copper pipe cap may be fasioned into one.

[jeeptechfred]

I totaly need to go look at my stove!!

[ampfab]

check out this link:
http://electrontubestore.com/index.php? ... cts_id=931

edit: darn, not in stock

[jeeptechfred]

That would have been great if in stock. I think I may have come up with a piece fabricated from a conduit adaptor. Ill post a pic if it works out

[gingertube]

I have no experience with teh metal jacket 6J7 but quite a bit with the glass 6J7G.

They are "fiddly" to keep out of parasitic oscillation.
I use the 2 piece metal shields on them (which you won't need with the metal jacket type) but have never found it necesary to shield the grid top cap.
I run coax up to a ceramic top cap, shiled stops 2 or 3 mm back from teh top cap, coax cetre wire is made to the top cap via a 10K surface mount resistor, that is the 10K is is in series and is a grid stop resistor.

Occassionally needed to add anode and screen stops too (100 Ohms) and on one particularly nasty case finally resorted to a 15pF wired anode to cathode (in addition to all the above).

So why bother - coz 6J7 sound stunning, still sound stunning when triode strapped.

This schematic (from 1942) does not show all the above additions or a 15K grid stop on the 6V6 Output Tube but shows a lovely 6J7 + 6V6 amp that I restored for a local guy. It was glorious with my Telecaster despite being a "Harmonica" Amplifier.

Cheers,
Ian

[jeeptechfred]

I did find I need a cap to keep ossilation down, I think I'm kinda close to the phase invertor tube.
I ended up creating one out of a 1/2" conduit connector with a freeze plug pressed on to the top. I followed up by drizzling epoxy inside to help glue the cap on and I also smeared the inside with a layer to insulate it. I installed a set screw where the regular screw went. Then I painted it. Seems to work well.