[Milsurplus] SCR-522: Receiver Surprises

[Bruce Gentry]

There are a few ways to de-gas a tube if the getters are still all 
silver. If the getters are reduced in size, turned milkey, or have  
substantial brown or dark gray edges, the chances of de-gassing are not 
good. One method  is to put the tube into an oven at about 250 degrees 
with the filament lit at normal voltage for a few days. Another is to 
connect a neon sign transformer with one lead to the plate and the other 
to all the remaining elements with no filament voltage. Use a Variac on 
the primary of the transformer  to bring the voltage up slowly until you 
get a glow, then reduce it until the glow is very weak. Leave it alone 
until the glow disappears, then repeat. Measure or calculate the voltage 
applied and don't go over about 150% of the tubes rated voltage. Another 
way  is to apply full filament voltage but reduced plate and screen 
voltage to the tube in circuit.  Again, increase until there is a weak 
glow, and let the tube cook until the glow stops. Repeat until the tube 
is operating at full voltage. I have been successful doing this most of 
the time, especially with VT-4/211s and 845s .  It take patience, but is 
better than searching for and paying for replacements, and preserves the 
tubes we already have that are very unlikely to ever be produced again.

      Bruce Gentry  KA2IVY


On 7/14/18 7:33 AM, arc5 at ix.netcom.com wrote:
>
> Still got a couple of open bypasses to replace in the if, when I get 
> some time. But this old Warrior's receiver surprises me. It's doing 
> considerably better than specified sensitivity. About 1.5 microvolts, 
> which isn't bad for a 9003 RF amplifier. Easily enough to listen to 
> local traffic. Next step is to etch some crystals to get them on the 
> right frequency. Transmitter's putting out a little over four Watts. 
> I'm finding some 832 tubes- even New Old Stock ones are becoming 
> gassy. I put one in and keyed the transmitter and got a beautiful blue 
> glow until the tube exploded. I've never seen that happen before. 
> Should have tested it first I guess.
>
>
>
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