Re: 147 8ohm load resistor - a question...

[Theo Fokkema <theo.fokkema@tip.nl>]

>> >>Still on 147's: The 6550 tubes have a mirror-like enamelling on large areas
>> >>of the glass - is this normal? (Leslie is circa 1973).
>>
>> This is normal, this comes from parts of the glowing wires of the tubes
>> coming loose and sticking to the glass, but it means that the tubes are
>> wearing. But you can continue using them as long as they work.
>>
>
>This is what is called 'A getter burn.'
>
>The following is from the Allied Radio Corporation 'Dictionary of Electronic
>Terms' First Printing, Feb 1956
>
>getter.  An alkali or alkaline earth metal introduced into a vacuum tube during
>manufacture and vaporized after the tube has been evacuated.  When vaporized it
>absorbs any gases which may have been left by the vacuum pump.  The silvery
>deposit in the glass envelope, vsually near the tube base, is the result of
getter
>action.
>
>John

As that dictionary says, the silvery deposit is visible near _the tube
base_, even with new tubes since it came there in the manufacturing process.
But here we were talking about large areas of the glass...