Hi,
To overcome this troublesome issue with different threading I am now
soldering all my coolers to the anode. Soldering/delsoldering is simple and
I now have no difficulties accomodating any type of 7289's.
And no leaks... !!!!
73 de Peter/SM2CEW
http://home.interact.se/~w100088/sm2cew.htm
At 18:35 1999-05-12 +0200, you wrote:
>
>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
>
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>
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