[Amps] 1625SS

[k7fm]

A few weeks ago, there was some discussion of the 1625.  I started reviewing 
my old QST magazines (my wife thinks keeping them on the book shelf is a 
waste of space) and found a tube announcement for the 1625.  It took awhile, 
because I got sidetracked by the many other articles and ads.  Well, I did 
not find the 1625 tube.

Last night I brought home a real treasure - a newly purchased Hallicrafters 
S-30, a very rare radio direction finder.  I was looking through the same 
QSTs to find an ad that showed a photo of the external power supply and 
finally found a birth announcement for the 1625.  It is in QST, February 
1941.  The announcement simply says that "the type 1625 is similar to the 
type 807 except that it is provided with a 12.6 volt heater and a 7-pin 
base."  So, the information adds little except a time frame.  More useful, 
though, may be the announcement of the 1626 in the same article.  This is 
much more unique.  It is designed for rf oscillator service "requiring 
unusual stability".  It is a new design and not a copy of one of the 6 volt 
tubes.  If you carefully examine the sequencing and timeing of the 16XX 
series tubes, you will find that they were released to solve a special need. 
It was not simply a 12 volt series of tubes.  For example, the 1624 2.5 volt 
filament, as I recall.  I expect the 1625 and 1626 were designed by RCA to 
meet specifications for a particular transmitter series.  I would guess that 
soon after, the 1629 was released.  It is almost as if these tubes were 
designed to meet the specifications set forth by the designers of the ARC-5.

Well, back to work so I can finish the 1941 QST binder before work.

73,  Colin  K7FM