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Old 22nd Oct 2021, 9:33 am   #1
G4YVM David
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Default Valve colours

Question, Among these valves I have to sort and sell (apologies for huge delays, a house fire and subsequent repairs are slowing me right down) I have a few that are fully coated externally with red coating, some with green coating. They look truly beautiful but resumably they werent coated for that reason. Can someone say what it is and why it was done? Im assuming it's to keep something IN rather than out, but why the pretty colours?

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Old 22nd Oct 2021, 9:43 am   #2
Nuvistor
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Default Re: Valve colours

The red coating on some valves was conductive and used for screening, grey coating was also used. I have not seen green. Mullard used red, perhaps marketing has the EF50 valve had a metal cover that was painted red.
See EF39 for the conductive coating connection pin 1

http://www.r-type.org/exhib/aad0089.htm
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Old 22nd Oct 2021, 9:56 am   #3
Cobaltblue
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Default Re: Valve colours

I have seen Green coated valves on some war era battery portables the other colour you see a lot pre war was Gold particularly Mullard.

Red and grey are still the most common.

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Old 22nd Oct 2021, 1:00 pm   #4
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Default Re: Valve colours

Ah yes, I have a gold one too...beautiful.

I have considered building a small display stand to show off these beauties.
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Old 22nd Oct 2021, 1:11 pm   #5
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Default Re: Valve colours

Three (rather dusty) gold Mullard valves in a Philips 785 AX monoknob. They are rather pretty, aren't they?
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Old 22nd Oct 2021, 2:05 pm   #6
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Default Re: Valve colours

Very!
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Old 22nd Oct 2021, 2:36 pm   #7
G6Tanuki
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Default Re: Valve colours

A very pale green was used on some WWII 'CV' valves as found in the likes of the WS18 and WS38 - they were Mazda Octal type but with a parallel sided envelope rather than the usual Mazda shouldered bottle.
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Old 22nd Oct 2021, 5:40 pm   #8
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Default Re: Valve colours

The gold ones are really bright when they are NOS.
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