Explanation wanted - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 27th May 2011, 07:43 AM   #1
diyAudio Member
 
Join Date: Jan 2005
Location: Denmark
Default Explanation wanted

Hello

At Virtually The National Valve Museum I found the following opinion:

" Most 6C5s were of the metal-envelope type whereas most 6J5s were 'GT/G' and therefore suitable for a wider range of applications. "

Is there someone who can explain that

Regards

Benny
  Reply With Quote
Old 27th May 2011, 10:35 AM   #2
diyAudio Member
 
Alastair E's Avatar
 
Join Date: Feb 2004
Location: South Wales
First 6J5'swere metal, but the metal envelope process was expensive....

Cheaper to make 'em in glass....

In some applications, the envelope built up a charge and needed grounding, otherwise it could cause strange effects....
  Reply With Quote
Old 27th May 2011, 04:09 PM   #3
diyAudio Member
 
Join Date: May 2005
Location: California
Quote:
Originally Posted by Alastair E View Post
In some applications, the envelope built up a charge and needed grounding, otherwise it could cause strange effects....
Very true... The 1st tube amp I built used metal 6L6's and I didn't ground pin 1. Besides being very hot, the metal 6L6's would give a nasty shock if I accidentally touched them. I 1st thought that was the tube's way of warning me that they would burn me if I touched them!
  Reply With Quote
Old 27th May 2011, 04:58 PM   #4
diyAudio Member
 
Mr. Zenith's Avatar
 
Join Date: Aug 2009
Location: Central NC
It's also worth mentionng that when introduced in the mid '30's, the 6C5 and 6J5 were commonly used in RF applications. The metal envelope provided shielding without the use of a separate external tube shield. In the absence of proper shielding, stray capacitance can cause frequency shifts in glass tubes used at RF frequencies - not a good thing for steady reception.

Frank Jones' "Radio Handbook for 1936" has several receiver circuits that feature these tubes as RF amplifiers and oscillators.

Last edited by Mr. Zenith; 27th May 2011 at 05:02 PM.
  Reply With Quote
Old 28th May 2011, 01:55 AM   #5
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
The 1st tube amp I built used metal 6L6's and I didn't ground pin 1.
Back in high school we hot roddded some old Stromberg Carlson PA amps that were designed for 6L6GA's. We stuffed metal 6L6 into them because we had hundreds of NIB RCA's to play with. I learned the hard way that the old Stromberg used pin 1 as a tie point for all the screen dropping resistors. I also learned that Steppenwolf's second album cover conducts electricity, and flies like a Frisbee when it touches a 6L6.

Even then (1968) I determined that you CAN make a metal 6L6 tube glow red. Someone told me that I couldn't, so.... It takes a few Eico power supplies wired together and the paint smells bad as it peels off the can. Hint....put about 800 volts on the can with respect to the plate which is already glowing from the 400 volts applied without negative bias.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 28th May 2011, 02:08 AM   #6
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Quote:
Originally Posted by tubelab.com View Post
Back in high school we hot roddded some old Stromberg Carlson PA amps that were designed for 6L6GA's. We stuffed metal 6L6 into them because we had hundreds of NIB RCA's to play with. I learned the hard way that the old Stromberg used pin 1 as a tie point for all the screen dropping resistors. I also learned that Steppenwolf's second album cover conducts electricity, and flies like a Frisbee when it touches a 6L6.

Even then (1968) I determined that you CAN make a metal 6L6 tube glow red. Someone told me that I couldn't, so.... It takes a few Eico power supplies wired together and the paint smells bad as it peels off the can. Hint....put about 800 volts on the can with respect to the plate which is already glowing from the 400 volts applied without negative bias.
Put it head down into the oil, and you have very linear tube. I don't know how RCA designed it, but it's linear mode is when it's plate dissipates about 150W.
__________________
"Our youth [...] have bad manners, contempt for authority; they show disrespect for their elders, contradict their parents, [...] and tyrannize their teachers. -- Plato, 447-367 BCE
  Reply With Quote
Old 28th May 2011, 02:52 AM   #7
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
Put it head down into the oil,
Metal 6L6's were very common surplus items after WWII. The old time ham radio operators used to run oil cooled 6L6's and crank about 100 to 150 watts of RF power from them on 40 meters in class C. I doubt that you could get ANY 6L6 tybe to DISSIPATE 150 watts for long, even in oil.

We had hundreds of new surplus RCA metal 6L6's in our high school electronics class. They all came from Homestead Air Force base surplus. I personally blew up several dozen. I tried water cooling to increase power and saw that old Stromberg amp (also Air Force scrap) crank out over 200 watts from 4 metal 6L6's and several Eico power supplies in series parallel. I don't know how much the water helped, but it kept the smell of burning paint below the teachers threshold for screaming at us.

The first picture shows a 6L6GC dissipating 44 watts. The 6L6GC is rated for 25 to 30 watts depending on whose data you believe. The metal 6L6 is rated for 19 watts.

The second picture shows a 6BQ6GA at 60 watts it didn't last too long.
Attached Images
File Type: jpg 6L6GC_44watts.jpg (114.0 KB, 137 views)
File Type: jpg 6BQ6GA_cranked.jpg (279.8 KB, 134 views)
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 28th May 2011, 04:25 AM   #8
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Quote:
Originally Posted by tubelab.com View Post
Metal 6L6's were very common surplus items after WWII. The old time ham radio operators used to run oil cooled 6L6's and crank about 100 to 150 watts of RF power from them on 40 meters in class C. I doubt that you could get ANY 6L6 tybe to DISSIPATE 150 watts for long, even in oil.
That means, they never saw the real linear life. Poor toobeys.
__________________
"Our youth [...] have bad manners, contempt for authority; they show disrespect for their elders, contradict their parents, [...] and tyrannize their teachers. -- Plato, 447-367 BCE
  Reply With Quote
Old 28th May 2011, 02:37 PM   #9
diyAudio Member
 
Troncones's Avatar
 
Join Date: Dec 2009
Location: Orange County, California.
Tubelab you definately live by the rule "Smoke em if you got em"
__________________
The Myth: A hand full of Tubes, Caps, Resistors and Iron and you have an Amp. The Reality: You have self induced Dementia. Newbie.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Schematic explanation johnnystulic2004 Solid State 1 20th October 2010 04:11 PM
Circuit explanation sites freakyone Everything Else 5 15th November 2007 10:01 AM
Explanation for this problem? Rob11966 Tubes / Valves 4 22nd September 2007 04:39 AM
Explanation of Self Oscillating Class D Genomerics Class D 19 29th October 2006 04:31 AM
Class D Multiphase explanation rtarbell Class D 2 9th January 2006 06:12 PM


New To Site? Need Help?

All times are GMT. The time now is 01:32 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2