[Milsurplus] 2X2 question

[J. Forster]

jmfranke wrote:

> Jack,
>
> The manual, AN 16-40SCR718-3,  for the SCR-718 radio altimeter has a warning
> on page 5-13 concerning some 2X2 rectifiers.
>
> "Some JAN-2X2 tubes made by the National Union Company will become gassy
> (indicated by a bluish glow) after several minutes of operation.  Do not use
> these tubes as they will shortly cause the high-voltage power transformer to
> fail.  National Union JAN-2X2 tubes made in Canada (indicated by a maple
> leaf marking) have been found free of this trouble)."

This sounds like a materials problem. The gas adsorbed on the electrodes leaves
the surface when the tube heats up. The glow further heats the electrodes
causing more gas to be evolved. High voltage transformers have fine wire and
could well overheat easily. Thanks VERY MUCH for this note, as I collect a
number of systems with 2X2s in them (BC-929-A among others) I already have one
with a bad power transformer due to pilot error.-John

> I believe the power transformer fails due to excessive current.
>
> The 2X2 was in the display indicator.
>
> Good luck with your project which sounds like ARQ-5 receivers.  I have two
> and was thinking of getting them operational.
>
> John WA4WDL