Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: Prev 1 [2]   Go Down
  Print  
Author Topic: Where can I buy GLASS 6AG7 tubes?  (Read 1121 times)
K1ZJH
Member

Posts: 1074




Ignore
« Reply #15 on: October 17, 2014, 01:38:26 PM »

That is a good idea Tim, I did not realize 6V6's were glass too. They might not be "as good" as oscillator tubes, but this is a 80/40 transmitter only. Since I already have ONE 6AG7/6L6, maybe I will convert the other one to a 6V6/6L6 and see how it works. And I already have metal 6V6 tubes, so can see how bad the two glass tubes interact.

Now I have something to do this weekend.

p

I mentioned that earlier... if the suffix is G or GT, the tube is glass.

Pete
Logged
K3STX
Member

Posts: 994




Ignore
« Reply #16 on: October 17, 2014, 01:56:21 PM »

I mentioned that earlier... if the suffix is G or GT, the tube is glass.

Pete

Yes, however when you said it I ignored you  Grin

I did not know how attractive the 6V6G tubes were, it is worth a try. I searched on Google under 6AG7G and saw a tube listed in "images", perhaps that was an error in the tube designation as that was the ONLY image I saw of a "6AG7G" tube.

paul
Logged
G3RZP
Member

Posts: 4713




Ignore
« Reply #17 on: October 18, 2014, 02:11:51 AM »

K1ZJH,

Pete, look at this data sheet..

http://frank.pocnet.net/sheets/095/6/6P9P.pdf

Nothing like the eBay pic......

73

Peter G3RZP
Logged
K1ZJH
Member

Posts: 1074




Ignore
« Reply #18 on: October 18, 2014, 07:09:29 AM »

Peter

Interesting! It is a glass tube in a metal shell. The only other example I can think of is the 0Z4 used in auto radios--they were also glass tubes with a metal shell over them.

The tubes in my link appear to be Chinese knockoffs?

Pete
Logged
G3RZP
Member

Posts: 4713




Ignore
« Reply #19 on: October 18, 2014, 07:45:10 AM »

Pete,

The 6P9P is Chinese, and as you say, glass tube in a metal shell. Philips/Mullard did a series of tubes like that - the EF50, which was originally meant for TV sets and was manufactured in millions in WW2, even in the US by Sylvania (the red Sylvanias were supposed to be the best), the EF54 which was a VHF amplifier pentode, predecessor to the 6AK5, the RL34 (very rare) a GG receiving triode and the EF55 which was pretty much a 6AG7. All on a 9 pin base, with no pinch, like miniature tubes.

There is a story, probably apocryphal, that the EF50 samples, designs and drawings were driven out of Eindhoven and taken to England as the German army entered the other side of the town. But the EF50 was the mainstay of a lot of the early radars, and post WW2, the TV sets after TV started again. A lot were used in 'Colossus', the computer used at Bletchley Park to break the German Enigma code. They were quite good in circuits such as the Phantastron and in Miller-Transitron timebases too.

So I wonder how close that eBay 6AG7 really is to a 6AG7..........Having had tubes from Eastern Europe, marked as 6BA6 but with cathode and suppressor grids strapped internally, I have suspicions...
Logged
AC5UP
Member

Posts: 3891




Ignore
« Reply #20 on: October 18, 2014, 08:04:08 AM »

Interesting! It is a glass tube in a metal shell. The only other example I can think of is the 0Z4 used in auto radios--they were also glass tubes with a metal shell over them.

The next time you have a metal 6SK7, 6SQ7, 6SJ7, etc headed for the circular file, pry the base off to see what's inside.

It's a glass tube in a metal shell.



This is what a shielded 6K7, 6Q7, 6J7, etc looked like before RCA decided to simplify the concept with the 'S' version of the same tubes. No separate grid cap, shield factory installed.



'Taint nothin' new.   Cheesy
Logged

Never change a password on a Friday                
G3RZP
Member

Posts: 4713




Ignore
« Reply #21 on: October 18, 2014, 08:09:45 AM »

I have opened a number of metal tubes and found them like the illustration in Terman - no glass tube inside.
Logged
K1ZJH
Member

Posts: 1074




Ignore
« Reply #22 on: October 18, 2014, 08:34:13 AM »

I have opened a number of metal tubes and found them like the illustration in Terman - no glass tube inside.

That is what I've always found as well. With very few exceptions, the metal 0Z4 being one of them.

AC5UP seems to be confusing metal tubes vs. glass tubes using an exterior metal goat shields, or similar.

The original octal based tubes were all metal and introduced by RCA. They were self shielding, using pin one for the shield connection. When competitors starting offering glass octal tubes in G and GT versions, the need for the external shield became necessary. BTW, those goat shield examples (labelled form fitting) were used on tubes with ST envelopes, which were not octal based and predated the RCA metal tubes.  Just because a tube has a shield does not make it a metal tube.

http://www.r-type.org/articles/art-018.htm

Pete
« Last Edit: October 18, 2014, 08:47:41 AM by K1ZJH » Logged
AC5UP
Member

Posts: 3891




Ignore
« Reply #23 on: October 18, 2014, 11:24:40 AM »

Thanks for the link to the 6J5 teardown....

It was years ago that I removed the base of an RCA metal tube to find a glass bottom plate and assumed it was a complete glass tube inside a metal shell.  If the glass could be sized consistently it wouldn't take much to build the shields ever so slightly smaller, heat them enough to expand a bit, then slip the glass inside as the shield contracted around it.  Permanent jam fit.  Next time I have a metal tube headed for the trash I'll take it for a spin with a tubing cutter to see what pops up.  Learn something new every day.

BTW:  Back in the day magnetic CRT shields were made from " Mu Metal " which was probably a bit pricey for common tubes.  http://en.wikipedia.org/wiki/Mu-metal  I've seen rusted 6J7's and similar so the shield material was probably nothing exotic.
Logged

Never change a password on a Friday                
K1ZJH
Member

Posts: 1074




Ignore
« Reply #24 on: October 18, 2014, 11:46:03 AM »

There were some new manufacturer "metal" tubes that had miniature glass tubes hidden inside!  I assume they were specially made for military contracts. I've seen a few photos of them posted over on the antiqueradios.com website.

If you want to see a really odd metal tube, Google birdcage 5Z4.  The first RCA versions had two exposed metal plate anodes, surrounded with a circular metal grille to prevent electrocuting service folks while allowing some ventilation.  They were only made for a year or so, but there was reliability issues and they went over to the more conventional metal shell with internal anodes.

Perhaps Peter can comment, but I remember reading that the Brit's had produced metal tubes before RCA came up with the octal design.

Pete
Logged
G3RZP
Member

Posts: 4713




Ignore
« Reply #25 on: Yesterday at 07:06:43 AM »

Back in the 1920s, the M-O (Marconi-Osram) valve company (MOV) produced some big water cooled transmitting valves, with numbers like CAT1, CAT2 etc., the 'CAT' standing for 'Cooled Anode Transmitting'. By the end of the 1920s with the broadcast receiver market taking off, they were looking at methods of reducing costs and produced some receiving valves with a metal envelope which was also the plate. For screening and safety, these were mainly in perforated thin metal cases - but not so much the AF valves. At the time, the pretty much de facto standard for heaters (as opposed to filaments) was 4 volts: 6.3 came a bit later from the US being good for car radios. These valves, with a relationship to the big CAT series were whimsically called 'catkins', and were all on the standard British 5 and 7 pin bases.

RCA went a different route with a mild steel envelope and eyelets of a special glass called FerNiCo (Iron, Nickel, Cobalt) which matched the thermal expansion of the steel. The metal tubes could be exhausted with envelope heated to red heat, which helped to get rid of absorbed gas, had very good screening and were more robust. They tended to be smaller - compare a metal 6J5 with a 6J5G - but as both MOV and RCA found, they were more expensive. Glass is pretty cheap when compared with even mild steel....although special types of glass are not necessarily so. Thinking here of the high temperature 'Nonex' glass used for things like Eimac 35Ts and the like, which tubes with their tantalum plates were run white hot as the tantalum absorbed the gas.

AFAIK, only Tung-Sol produced GT versions of the 6SG7 and 6SH7 (which are basically the octal predecessors of the 6BA6 and 6AU6 respectively). Possibly this is because they wanted cheaper tubes for use in FM receivers...All the other manufacturers only did them in metal. Yet nobody ever did a 6SN7 or 6SL7 in other than GT versions...
Logged
K1ZJH
Member

Posts: 1074




Ignore
« Reply #26 on: Yesterday at 09:34:04 PM »

ZGP:  Yes, I think those are the ones I heard about, and someone mentioned they were called "catkin" tubes for some odd reason.

Pete
Logged
G3RZP
Member

Posts: 4713




Ignore
« Reply #27 on: Today at 12:07:49 AM »

Pete,

Now you know why they were called 'catkins' - little cats!

Meouw....
Logged
Pages: Prev 1 [2]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!