[Boatanchors] 4-1000A coloration ?

[Rob Atkinson]

if you do it right you can degas them.


rob
k5uj

On Mon, Jan 2, 2012 at 1:19 PM, Jim Wiley <jwiley at alaska.net> wrote:
> What you re seeing i mist likely due to electron bombardment of the
> glass, not unlike the way sunlight sometimes changes glass telegraph
> pole insulators to green or violet.   Is a sign of use, but not
> necessarily a problem, if the tubes were operated within their ratings
> and with sufficient cooling air.
>
>
> If operated conservatively, a 4-1000 or similar tube will last for
> several tens of years.  The biggest problem is excessive filament
> voltage, which can damage the emitting surface, and excessive drive,
> which can damage the grid.  Unfortunately, the only real way to test
> them is to install the tube in an operating amplifier and see how it
> does.  If it glows purple inside ( between the filament and plate), it
> is gassy, and probably should not be used.  Purple glow from the glass
> is OK - that glow is again due to electron bombardment
>
>
> - Jim, KL7CC
>
> .
>
> Paul Baldock wrote:
>> I have just acquired three 4-1000A's. On each the inside of the glass
>> has a yellow discoloration in places, it looks a little like varnish.
>> Is this normal?
>>
>> Thanks
>>
>> - Paul
>>
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