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Old 26th May 2020, 12:23 pm   #1
longneck90
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Default Cossor valve 220 O.T.

Hello to all. I would be grateful if some Forum Member could give me some advice on this valve. I removed this valve from a Cossor, Model 30 and was puzzled by the area around the base pins. There is a hole there, as if an extra pin had been removed. I am able to insert an insulated wire through this hole, and right up, inside the glass envelope. I was wondering if that is the way it should be. Thanks in advance. All the best. John.
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Old 26th May 2020, 12:40 pm   #2
John M0GLN
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Default Re: Cossor valve 220 O.T.

Quote:
Originally Posted by longneck90 View Post

I am able to insert an insulated wire through this hole, and right up, inside the glass envelope.
Actually inside the glass envelope or just into the plastic base? if the former the valve envelope is broken and the valve is useless, I've just looked at all my valves with bases like yours and they all have holes of some type in them.

John
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Old 26th May 2020, 12:47 pm   #3
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Default Re: Cossor valve 220 O.T.

When you say you can insert a wire and see it in the glass envelope, can you see it in the 'pinch' tube or actually in the envelope with the anode?

What colour is the getter deposit?
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Old 26th May 2020, 1:32 pm   #4
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Default Re: Cossor valve 220 O.T.

The 220 OT is a battery (2v 0.2A) Tetrode on a B5 base, so only has 5 connections.
Nothing has ever been in the 'spare' hole. Why it is there... no idea.
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Old 26th May 2020, 2:59 pm   #5
John M0GLN
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Default Re: Cossor valve 220 O.T.

Quote:
Originally Posted by snowman_al View Post
Nothing has ever been in the 'spare' hole. Why it is there... no idea.
Nearly all of mine have some sort of hole in them but I don't why, below are 4 typical ones.

John
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Old 26th May 2020, 2:59 pm   #6
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Default Re: Cossor valve 220 O.T.

Its position is similar to below where the side screw terminal might go on the side of the base of a B5 Pentode.

It might be there to make it easier to connect the side terminal on the base when used on a Pentode during manufacture.

Easier to make 1 base rather than many if you don't need the hole nothing lost.

Just an observation.

Cheers

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Old 26th May 2020, 7:02 pm   #7
longneck90
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Default Re: Cossor valve 220 O.T.

Hello to all. Thanks for all your advice. I took another photo. Hopefully, the red wire can be seen 'inside' the valve. I just don't know if it should have access to there. All the best' John.
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Old 26th May 2020, 7:11 pm   #8
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Default Re: Cossor valve 220 O.T.

Hi John

Yes that's the pinch.

If you watch how this style old valve is made it will become obvious.

https://www.youtube.com/watch?v=_-JzxX75oYc&t=1116s from about 12 minutes in

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Old 26th May 2020, 7:37 pm   #9
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Default Re: Cossor valve 220 O.T.

The pins look like they could do with some solder.
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Old 26th May 2020, 8:18 pm   #10
longneck90
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Default Re: Cossor valve 220 O.T.

Hello to all. Thanks for all your various replies and advice. The 'Modern Aladdin's Lamp' video was totally interesting. Thanks to Mike T for highlighting it. All the best. John.
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Old 26th May 2020, 8:25 pm   #11
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Default Re: Cossor valve 220 O.T.

At a guess it's to stop an air pocket disturbing the shellac (?) adhesive whilst it cures.
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Old 26th May 2020, 9:53 pm   #12
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Default Re: Cossor valve 220 O.T.

As my chidhood neighbour (he was in photo recon in WW2) said to ladies looking at the "pee hole" in old biplanes "What's that hole for?", answer "Lightness madam, lightness". I think the shellac idea is good but the pins have holes down them anyway.
 
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