[AMPS] 7289's and other uWave tubes

[John Fielding]

Hi all - a slightly off-topic question.

I am updating my 23cm station for eme and converting the various tubes to water cooling. 
A question regarding the thread which is used to attach the air-finned cooler to the
tube anode.  

In Chip Angle's N6CA article for a water cooled 7289 amplifier he states that the
thread is 3/8"x16 which I assumed (incorrectly) was UNC.  However when I measured the
several tubes I had stripped the thread appears to be BSW (Whitworth).  Can someone
confirm this before I spend my hard earned cash on an expensive tap and die?

BTW Several of the tubes I have are made by Siemens which use 2 different thread forms,
one is similar to the USA style but appears to be 12mm but a finer pitch than standard. 
The other type uses an inverse thread, the cooler is threaded on the outer part unlike
the normal types which are threaded internally.  Anyone care to comment what these
threads might be?

I have also designed a water cooling jacket for the Russian GI7bt triode which bolts on
in place of the air-finned cooler.  If anyone is interested I will send details on
request.

Thanks in anticipation.

John	ZS5JF

--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm