Origin of the 6L6GC?

[Rhodesplyr]

Which is oldest the 6L6, or the 5881, and what is the big difference?

As Tom said, the 6L6 came first. Here's a copy of an article from Radio & Television News, September 1950:

ts5881s.pdf

Previously, there had been the metal 6L6 and one or two glass versions.

[Tom Phillips]

...copy of an article from Radio & Television News, September 1950...

Thanks so much for that post. The article includes a lot of information about tube construction relating to service life, maintaining the hard vacuum and the problem caused by operating a tube with the heater powered and the B+ off. That last point will be of interest to those who participate in the many discussions about the pros and cons of using a standby switch. The problem has been discussed before but the article describes the processes in play in a clearer way. At least to me anyway.

The scan does not show the publication date. How do you know it was from Sep 1950?

The estimated 1950 price mentioned was $3.50US. That would be about $35.00US in today's dollars which I would gladly pay for a tube of the described quality.

Thanks again,
Tom

[km6xz]

Nickel plating was done very early in power tubes but was not cost effective in "receiving tubes" which all consumer type tubes were(are) called. These went into consumer radios, phonographs etc and a 6L6 was price sensitive being intended for consumer products.

The nickel/carbon plates in industrial and RF tubes was also a cost savings from the machined solid graphite anode structures. Being directly heated and not needing getters made power tubes simpler in construction but had room for beefy components. The red or cheery glowing plates in normal operation served as a full time getter.

[Rhodesplyr]

My assumption is that this site got the publication date right:

5881, A new Beam Power Tube

[bob p]

...and the problem caused by operating a tube with the heater powered and the B+ off. That last point will be of interest to those who participate in the many discussions about the pros and cons of using a standby switch.

IMO that last point should also be of interest to those who like the idea of switching off a pair of power tubes using a cathode interruptor, for things like 50/100W switching.

I've always thought that the 50/100W switch was a really bad idea. People are inclined to leave an amp in a 50W setting for protracted periods, under the illusion that they're cutting half of the output power and sparing those two tubes. In reality, they're still burning off the cathode coating on the two tubes that aren't getting used. The half-power switch encourages people to populate an amp with 4 tubes, burn up 4 tubes, and get the benefit of only 2 tubes. Seems like a lose-lose situation. Pulling the unused tubes or switching off the heaters seems like it would be a better approach.

[Old Tele man]

RCA introduced the 6L6 in July 1936: http://www.clarisonus.com/Archives/T...er%20Tubes.pdf

[Leo_Gnardo]

Had a brain-wave that 6L6 were developed as an affordable and/or toughened version of WE's 350B. Anybody familiar with the 350B? Latest seen selling for @ $850 each. There is an "affordable" version from Valve Art but I suspect it's a China 6L6 in a light bulb bottle.

[Old Tele man]

Had a brain-wave that 6L6 were developed as an affordable and/or toughened version of WE's 350B. Anybody familiar with the 350B? Latest seen selling for @ $850 each. There is an "affordable" version from Valve Art but I suspect it's a China 6L6 in a light bulb bottle.

Other way around...the WE 350B was developed from the RCA beam-tetrode 6L6 for better radio frequency utilization.

[Leo_Gnardo]

Other way around...the WE 350B was developed from the RCA beam-tetrode 6L6 for better radio frequency utilization.

Thanks for clearing that up. Also for the link - fascinating!

[Old Tele man]

For those interested in the technical aspects of the 6L6 beam power tetrode, see page 656 in this 1962 in-house RCA document:

http://www.tubebooks.org/Books/Atwoo...e%20Design.pdf

[Jazz P Bass]

Can't get the link to open

[Tom Phillips]

Can't get the link to open

Worked for me yesterday and still works today. However it takes a long time to download the 86MB file. Then it appeared to be dead until I saved it to my local disk and then opened the saved file.