Tag Archives: Vacuum Tubes

Brass Pin on the side of 811A and 572B Tubes

Not every power tube installation uses a simple push-in tube socket.

A straight-push insert replacement socket

Some older ham gear, audio gear and military/avionic sockets are twist-type.

Twist-Insert Socket – look for the pin guide slot in the collar

As something has to fit the index slot, a Brass Pin on the side of 811A and 572B Tubes is a mechanical index and retention pin.

Brass Indexing Pin (on an 811A)

These sockets where you have you insert the tube base with the pin in an L-shaped slot, Push in And then Rotate are kind of neat.

Looking down into a twist-type socket

Most old tubes have a pin that sticks out about 60-70/1000th of an inch.   A small group of original 811A tubes from my amps that W9KR measured showed .062” to .071”.

The pin length on new tubes may vary, as I received 572B tubes with an exposed 94/1000th of an inch of pin which is sticks out too far for one  of the socket locations in my amps, as the overly long pin doesn’t quite clear other components and chassis in my amplifiers.  The 572B tubes W9KR measured .091” to .094” pin extension lengths.

I have not been able to find an original specification for pin length.

When confronted with an overly long pin that hits chassis or components, a bit of Dremel tool time, relieving the excess pin length or sanding away the entire projecting pin, will sort things out.



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Tubes and Spare Tubes – Collins Edition

As my two Collins S-Line stations received tremendous amounts of TLC at the hands of Chuck W9KR, the vacuum tubes were checked with any out of specification replaced.

I am planning to buy at least one complete backup set as reserves.

Tubes are not “forever” items, and a ham would not even have a chance of a quick repair if you didn’t have spares on hand.

One of decisions is to what depth should I put in spares?  Would one comprehensive set between the two stations be sufficient?  Or one comeplete set PER station?  Or greater depth of all or perhaps just certain tubes?

Be careful about how your suppliers ship your tubes. One box ordered looked like it was place-kicked at the USPS perhaps in an afterhours soccer match! Amazingly the tubes all survived and tested okay.

I am looking for advice on storing spare tubes, especially as some become rather rare and expensive. Any time-proven methods?



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Will the New USA Audio Tube Initiative spill over to Ham Radio?

There are some good things happening in the world of top-notch Audiophile Vacuum Tubes:

Exclusive: Western Electric confirms plans to tackle the tube crisis with its Georgia factory

Basically their 300B production will be expanded to include 6L6, EL34, 6V6, EL84, 12AX7 and other audiophile grade tubes.

Presently their production is considered “Ultra-Premium” and is priced accordingly to the level of TLC and technical perfection Western Electric brings to the vacuum tube game.

Western Electric is actually a new company that picked up the heritage and licensing of the original.

Here is a link to the website for the plant:


And a link about the audio tubes they are successful in producing:


In the RF world it may not be possible to support an Ultra-Premium product and pricing, but there is room for a high quality.

Could the growth in range eventually include radio vacuum tubes?

Would sure be nice!



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