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

donate to eham
   Home   Help Search  
Pages: [1] 2 3 Next   Go Down
  Print  
Author Topic: Where can I buy GLASS 6AG7 tubes?  (Read 25882 times)
K3STX
Member

Posts: 1644




Ignore
« on: October 17, 2014, 07:44:43 AM »

I want a glass one, but can not find a supplier. Anyone have ideas/one to spare? This is only to make my slatboard 6AG7/6L6 to look "cooler" than with that ugly black metal 6AG7. Either 6AG7G (preferred) or 6AG7GT.

paul
Logged
W1BR
Member

Posts: 4189




Ignore
« Reply #1 on: October 17, 2014, 08:01:18 AM »

You may have to go with a Russian 6P9 in a glass version. I have never seen a GT 6AG7 tube.

Pete


http://www.ebay.com/itm/Shuguang-6P9P-6AG7-Vacuum-Tube-Valve-/221306607995?pt=Vintage_Electronics_R2&hash=item3386e6d97b
Logged
AA4HA
Member

Posts: 2630




Ignore
« Reply #2 on: October 17, 2014, 08:11:50 AM »

The 6CL6 is a pretty close match. It was meant to be an all glass replacement for the 6AG7 octal-metal tube.

If your application requires the shielding you may need to add one anyway. the 6AG7 has a mutual conductance of around 11,000 uMohs. Pretty high gain for a small signal RF tube. (about 9 watts dissipation).
« Last Edit: October 17, 2014, 08:15:21 AM by AA4HA » Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
W1BR
Member

Posts: 4189




Ignore
« Reply #3 on: October 17, 2014, 08:31:37 AM »

One other small point, if you go with glass tubes, you may need to provide some shielding between the two tubes. Otherwise, the plate of the 6L6 can couple back to the plate of the driver stage, which is in essence the grid of the PA.  That can lead to all manner of instabilities.  The metal tubes are grounded via pin one on the sockets, and are self shielding.

Pete
Logged
K3STX
Member

Posts: 1644




Ignore
« Reply #4 on: October 17, 2014, 09:09:57 AM »

Ugh, that 6CL6 is a pretty ugly tube!

p
Logged
W1BR
Member

Posts: 4189




Ignore
« Reply #5 on: October 17, 2014, 09:22:48 AM »

Well, look for a design that uses a 6V6gt or 6V6g for the osc/driver.  A 6V6 or 6F6 should make a fine substitute with a small amount of changes.  Glass 6L6 tubes are not cheap either. You may want to consider going over to an 807.

Pete
Logged
K3STX
Member

Posts: 1644




Ignore
« Reply #6 on: October 17, 2014, 09:44:29 AM »

From what I have read the 6AG7 is far superior to a 6V6 or 6F6 oscillator. This was shown in an old QST article. And yes, that 6L6G did cost me about $10 but sure is pretty. The TX I am trying to "upgrade" is on my QRZ.com page.

paul
Logged
W1BR
Member

Posts: 4189




Ignore
« Reply #7 on: October 17, 2014, 09:51:41 AM »

Looking at those photos, how were you planning on avoiding unwanted coupling between the 6L6 plate back to the 6AG7 plate, if you did use glass tubes?

Pete
Logged
K3STX
Member

Posts: 1644




Ignore
« Reply #8 on: October 17, 2014, 10:01:33 AM »

i was gonna worry about one thing at a time, first get tube and then see if i have a problem that i have to fix.

p
Logged
W1BR
Member

Posts: 4189




Ignore
« Reply #9 on: October 17, 2014, 10:03:04 AM »

Good luck.  Nice looking home brews.

Pete
Logged
G3RZP
Member

Posts: 1278




Ignore
« Reply #10 on: October 17, 2014, 10:05:42 AM »

Looking at Frank's Tube Data site, he lists 6AG7s from various manufacturers including the RFT lot in what was the DDR (East Germany). None of them in glass. Just as nobody (including RFT) did a 6SN7 or 6SL7 in other than GT.

My conclusion is that nobody ever made a 6AG7 in other than a metal version.

The Russian 6P9 is in metal: the Chinese 6P9P apparently is a glass tube inside a metal sheel, a bit like and EF50.
« Last Edit: October 17, 2014, 10:09:05 AM by G3RZP » Logged
W1BR
Member

Posts: 4189




Ignore
« Reply #11 on: October 17, 2014, 10:15:33 AM »

Peter

Check this out:

http://www.ebay.com/itm/Shuguang-6P9P-6AG7-Vacuum-Tube-Valve-/221306607995?pt=Vintage_Electronics_R2&hash=item3386e6d97b
Logged
N3QE
Member

Posts: 5587




Ignore
« Reply #12 on: October 17, 2014, 11:27:30 AM »

Put a glass coke bottle over top the 6AG7 :-).

Or if your circuit will work with a slightly less "hot" tube, glass coke bottle 6V6's are decidedly cool.

Logged
K3STX
Member

Posts: 1644




Ignore
« Reply #13 on: October 17, 2014, 12:37:06 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
Logged
N3QE
Member

Posts: 5587




Ignore
« Reply #14 on: October 17, 2014, 12:53:25 PM »

They might not be "as good" as oscillator tubes

The approach to circuit design in the 40's/50's ARRL handbooks heavily emphasized a minimal number of high gain devices.

This can actually be a little tricky when the high gain devices tend to self-oscillate in some wacky modes (including UHF parasitics and/or squegging) if not everything is bypassed with extreme care.

A more modern approach is to use multiple stages of moderate gain, and especially to use some negative feedback at each stage to enhance stability.

A lot of the problems that were attributed to "not having a hot enough oscillator tube" or "not enough shielding" back then, were really because the simple designs ran the oscillator and PA and the antenna all at the same frequency. There is a substantial advantage to frequency doubling somewhere between the oscillator grid and antenna. Frequency multiplication provides incredibly more decoupling, than all the metal tubes and aluminum sheet metal ever could.

If you read the 50's handbooks they knew that transmitters that had electron coupled oscillators aka "tri-tet" which doubled or tripled at the oscillator tube plate, had substantial immunity to many problems that plagued the straight-through designs. They usually attributed this to the concept of "oscillator loading" but did not seem to realize that the real advantage was frequency multiplication.
« Last Edit: October 17, 2014, 12:58:55 PM by N3QE » Logged
Pages: [1] 2 3 Next   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!