Tube "Centerfolds"

"Eye Candy" for the tube collector

Silvertone 45A

The 45A was a larger bulb version of the 45, with an uprated output of 3 watts (vs. 1.6w from a standard 45). The plate voltage is rated at 325v (vs 275 for a standard 45). It may have been an attempt at bridging the gap between the 45 and 50 in output.

I have three examples in my collection - this beautiful pair with etched bases and a single printed base version, all branded Silvertone.

There is a bit of data on this tube at Jim de Kort's informative web page at www.vt52.com - well worth a visit!

If anyone has more data on the 45A (or wants to sell/swap one so I can complete my other set) please let me know.

WLS 2976

Sears Roebuck and Co. had a line of tubes equivalent to standard types and branded WLS. WLS was named after their Chicago radio station of the same name, after "World's Largest Store". The 2976 seen here was equivalent to the industry standard UX-201A.

There is a table of WLS tube types in Ludwell Sibley's "Tube Lore" - a necessary book in any tube collectors library. Sibley's book accompanies me to every radio show or hamfest.

6L6GX

The 6L6 has to be the most popular output tube of all times. Eric Barbour did a very nice history of the 6L6 in Vacuum Tube Valley issue #4. Originally introduced as a metal tube, there are literally hundreds of 6L6 versions and near cousins such as the WE350B, Mullard EL37 and GEC KT66.

The 6L6 pictured here is a GX, with a Isolantite base (ceramic). Ironically it was made only a few miles from here in Salem Mass, but I purchased it from someone in California. If anyone has a mate let me know - I'd love to do a bit of matchmaking!

A 715kb PDF file of the original RCA 6L6 specifications and curves from the HB3 is here for download

WE 437A / 6C45pi

This pair includes the elusive (and expensive) Western Electric 437A and the much more available Russian 6C45pi

Spec sheets for the 437A are on my Data Page.

There are some nice designs for the 6C45pi on PAE here including a one tube amplifier, available transformers and data. 

I purchased my 6C45pi tubes from Gintaras Sakenas who goes by LEMPOS on ebay.  His website is here.

5690

This 5690 is a rarely seen member of the RCA "Special RED" series of tubes. 

The family includes:

5690:  Full-wave rectifier, GT Octal, heaters 6.3v at 1.2A each, 1120 V PIV, 125 mA, Heaters and cathodes pinned-out individually.
5691:  Duotriode, 6SL7GT with heaters in series so that one failure will disable both sections in bridge circuits.  Heaters raised to 600 ma
5692:  Duotriode, 6SN7GT; derated to 1.7 W per section, heaters in series.
5693:  Pentode, 6SJ7

5881

    The 5881 was introduced in 1952, and received heavy use in military servo amplifiers. They are often also labeled 6L6WGB.  It is one of my favorite 6L6 variants, and was the original tube in the Heahkit WM-2, WM-3 and WM-4 amplifiers.  I also have seen 5881's made by Sylvania and RCA.

    It made use of a smaller bulb, and was much more rugged than a standard 6L6.  Compared to the original 6L6 (or 6L6G, 6L6GA, and 6L6GB) the plate dissipation was uprated from 19 to 23 watts.  The plates were painted with Zirconium to aid in gas absorption during the life of the tube. 

This article from Radio & Television News is by C.E. Atkins, an Engineer at Tung-Sol and details the release of the 5881.  The suggested retail price was $3.50!  The PDF file is around 1.2mb in size, you may want to "right click" on the link and save the file to your harddrive before viewing.

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