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Old 18th Jun 2019, 2:25 pm   #17
GrimJosef
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Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 4,310
Default Re: GZ32 rectifiers for a quad amp

Interesting. I think the cathode tubes are directly below the square holes in the mica aren't they ? It's as if the metal vapour is leaving the cathode tubes and passing to the glass through the square 'masks' in the mica. The mica is there as a mechanical support for the valve's separate electrodes. These need to be insulated from one another, obviously, and efforts were made, in some valves at least, to keep the getter film off the micas to avoid compromising their insulation. It looks like there would have been metal on the GZ37 mica around the edges of the square holes in this case though.

Cheers,

GJ
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