6sn7 single/individual tubes

pitdogg2

See that saucer getter at the bottom? Every Russian tube will have that style from my experience. So down the road when someone tries to sell you a tube from say Mullard and say it's from blackburn plant and it has a saucer you will know to walk away.

Clipdat

What part are you looking at specifically to see the "saucer getter" at the bottom?

pitdogg2 wrote: »

See that saucer getter at the bottom? Every Russian tube will have that style from my experience. So down the road when someone tries to sell you a tube from say Mullard and say it's from blackburn plant and it has a saucer you will know to walk away.

dkfreebird

I’m guessing this one.

Viking64

I'm confused. Do those things have snow in them when you shake them?

Clipdat

Got it! Thanks so much for pointing that out, appreciate it.

dkfreebird wrote: »

I’m guessing this one.

Clipdat

I'm about to shake YOU around and see if snow comes out.

Viking64 wrote: »

I'm confused. Do those things have snow in them when you shake them?

Viking64

Clipdat wrote: »

I'm about to shake YOU around and see if snow comes out.

Temper, temper. And why do you quote people backwards?

Clipdat

I'm not doing it backwards, you are.

Viking64 wrote: »

Temper, temper. And why do you quote people backwards?

pitdogg2

dkfreebird wrote: »

I’m guessing this one.

Yes correct. It's known as UFO or Saucer getter.

mhardy6647

Yup. The getter "gets" residual gases and volatile materials left over from manufacturing of the tube, to insure the "hardest" possible vacuum (both for the brand-new tube and over the life of the tube). The little electrons very much appreciate not havin' to bump into other things as they're going about their work, traveling from cathode to plate whilst gettin', shall we say, influenced by the grid.

The thing is, anything that is floatin' around within the tube can interact with the electron stream(s) in the tube and slow the electrons down and/or knock 'em off course. The getter's job is to get rid of as much of that flotsam (or is it jetsam?) as possible. At the very high vacuum levels inside of a tube, things that we don't normally think of as volatile are volatile! Thus the persistent need for the getter throughout the life of the tube.

We are used to seeing so-called "flashed getters" in many tubes. This is that silvery coating, somewhere on the glass, of barium metal that's deposited (evaporated) onto the glass during the manufacturing process. The flashed getters are useful 'vacuum indicators' -- if air gets into a tube, the silvery looking barium is converted to powdery white barium oxide (and the tube's kaput).

I don't know if the saucer in the Rooskie tube is the getter, or if it held the getter material during manufacture. My guess is the former, as the tube(s) in the pictures above don't seem to have a flashed getter(?).


stuff about getters.
http://www.tubebooks.org/file_downloads/Getter_Material.pdf

mhardy6647

ol' Marky the Inexcusably Slothlike finally made the trek all the way down the cellar stairs to check the plinker graveyard.

Here's one I would offer up* if the OP'd like it. A used Sylvania 6SN7GTB. A tall drink o' water, as my father would've said. Checks good for emissions, grid leakage and shorts (i.e., no grid leakage nor shorts!) on my hand-me-down Mighty-Mite III (no more, and no less, than a simple but dependable emissions-type tester)

I will use test it anon & send a PM to the OP -- but I wanted to share a coupla photos for... posterity.


DSC_0217 (2) by Mark Hardy, on Flickr
DSC_0214 (2) by Mark Hardy, on Flickr
DSC_0213 (2) by Mark Hardy, on Flickr

Viking64

mhardy6647 wrote: »

I will use test it anon & send a PM to the OP -- but I wanted to share a coupla photos for... posterity.

Wow! She's a beauty.

https://www.youtube.com/watch?v=mQ_k_VG6Syc

Clipdat

Oh hell yes. Excitement level rising!

PMing you

Clipdat

Few pics of the tubes that have been generously given to me for free by fellow Polkies.

First up is a pair of Silvertone tubes from @voltz . Love the writing on the base: "We guarantee this tube to give perfect satisfaction for one year. Sears Roebuck and Co."





Next up is a Sylvania tube from @mhardy6647 - look at how much taller it is than the Silvertones! Also, you can see that the tube part leaves the base at an angle. It's slightly crooked, which gives it immense character and uniqueness.




Thanks to both of you, I really owe you guys one!

mhardy6647

You are welcome (of course)
Have fun!

verb

Thanks Ivan for sharing this thread! Now that the Cary appears to be back in business, time to get my read on and travel down the 6SN7 path, as many of you have done before!

mhardy6647

The wonderful thing about 6SN7s is that there were zillions of them produced. I picked up a box of plinker tubes (pulls) from the freebie pile at NEARC last week. Along with some of the usual suspects*, there were three or four nice looking 6SN7s. Haven't tested them yet, but I woudn't be surprised if they're all good.

_______________
* e.g., 1B3 HV rectifiers from old monochrome CRT TVs of a long-gone era. Heck, even I can muster the gumption to throw those away!

verb

mhardy6647 wrote: »

The wonderful thing about 6SN7s is that there were zillions of them produced. I picked up a box of plinker tubes (pulls) from the freebie pile at NEARC last week. Along with some of the usual suspects*, there were three or four nice looking 6SN7s. Haven't tested them yet, but I woudn't be surprised if they're all good.

_______________
* e.g., 1B3 HV rectifiers from old monochrome CRT TVs of a long-gone era. Heck, even I can muster the gumption to throw those away!

So Doc, been getting some reading on the 6SN7 history, tube testers, and I'm struggling with the difference between "true" vs. "dynamic" transconductance. Help a newbie out please!

GlennDog

I think the good doctor is gonna blow up your inbox with reams of info!🤣🤣🤣🤣🤣

mhardy6647

I... I actually don't know the answer to his question

verb

Hey Mark, found this snippet in one of the technical articles linked below.



http://www.alltubetesters.com/articles/tester_guide.htm

mhardy6647

That snippet enters territory I am more familiar with.
I do agree with the author, though -- Hickok or the highway

You should get a refurbished and properly calibrated Hickok if you want to test tubes under 'actual' operating conditions (i.e., to match sections in twin triodes or to match pairs or quads of power tubes). They are not inexpensive, but buying a cheap Hickok is like buying a cheap used Mercedes

It's even better, I'd opine, to know someone with a good Hickok (like a TV-7).

The best test of a tube is to try it in the circuit in which you would like to use it!

I have a simple but battle-tested 'emission type' tester (Sencore Mighty Mite III, in my case). Useless for tube matching, but a reliable way to test the 'strength' of electron emission from the cathode. The Mighty Mites also feature a very good grid leakage test, plus a good test to detect shorted internal elements in a tube. This is a good 'first pass' test for plinkers (e.g., used/"pull"/foundling tubes) to protect a piece of expensive equipment from injury
These were mostly for the TV service market and lack sockets for early tubes (4, 5, 6, and 7 pin sockets for the old globe and "ST"/Coke Bottle shaped tubes prior to the octal/miniature base era) -- i.e., no 2A3 testin' with a stock Mighty Mite

DSC_0213 (2) by Mark Hardy, on Flickr

This one was my father's

The drug store tube testers were emissions testers and, first and foremost, were designed to sell tubes (if you catch my drift ).

verb

I remember going to the drugstore with my Dad with a shoebox full of TV tubes! Good memories!

verb

The TV-7 was my conclusion as well. According to what I've read, you take the reading and use the included chart (blue booklet) to covert to Gm.

verb

Another side note, I contacted my local vintage radio service store, of which they have done very good work for me in the past, including troubleshooting the VTL a while back, but was dismayed to discover the details of their tube checking service.

They charge $1/tube (reasonable) but only check to see if the tube is good or bad! They have many testers, including a Hickock (534 IIRC), but would not record the actual Gm values for me. WTH?!

I haggled with the guy for a bit, and got him to agree if I provided a table on a sheet of paper with the advertised Gm results, or NOS values, they would fill out the blank field in the table of the actual values!

I guess tube checking is not in their business model. Needless to say I was a little soured and dismayed.

verb

These came today!

Set of 4 NOS Sylvania's. According to some tutelage from one of our very own and subject matter expert @pitdogg2 these are 1958 (December) vintage, IIRC and was paying attention to his teaching!

verb

And, how could I resist! From my own company! Of a different era, of course!

Good view of the side mounted getter. Is the this the infamous "D" getter?

Funny @pitdogg2 as you mentioned, even the package is labled "GE"

verb

Here's a good pic of a GE tube with the same getter. Construction appears to be identical.

pitdogg2

I get a lucky guess from time to time I cannot get a good look at the getter. Some were round and some were horse shoe. Some were clipped around the plate edge.

1958 was my best guess due to the boxed label on the Sylvania tubes. Earlier tubes also had the chrome almost half way down the tube and some almost 3/4 down one side. Those are good tubes either way. Later tubes were made by Philips and had blue writing most of those are in the 1970's era

pitdogg2

More research has led to those are 1968 not 1958.
I fouled that one. Sorry Dave.
Sylvania started using yellow writing in the 60's and the last number of the year instead of the last two digits.
My early 50's up to 58 i have are green lettering and much more chrome. So much that you are not able to see the top of the plate or getter. They also say 5835 and 5214 as codes. They also have wider bases than those.
Strange my phone I can actually see that getter better than my laptop. That is a horseshoe getter.