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Identifying valves with no markings

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Re: Identifying valves with no markings

Post by Valvebloke » Tue Nov 20, 2012 4:15 pm

Do you have a wide spread of different ECC83 types ? When I went through the same process I was really surprised at how different two things which are supposed to behave 'the same' can be.

VB

 
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Re: Identifying valves with no markings

Post by freya » Tue Nov 20, 2012 4:19 pm

I would say about five different types, some have broad arrow marks on their bases but no other markings.


Stephen

 
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Re: Identifying valves with no markings

Post by Kalee20 » Tue Nov 20, 2012 6:34 pm

freya wrote:My problem is that on looking in my box of double triodes has lots that have no markings, is there an easy way of finding out if they are ECC82`s or ECC83`s by looking at the contsruction.
I know the ECC83 draws more anode current.


No - the ECC82 draws more current.

The trio ECC81, ECC82, ECC83 are similar to each other, and different from other B9A double triodes eg ECC85, PCC89 etc. As far as I know only the 81, 82, 83 have a tapped heater (with tap to pin 9).

If they are from the same manufacturer, you might be able to see enough of the grid to distinguish between an 82 and an 83. The ECC82 has a coarser pitch grid. You do need a decent light. I'm not quite sure where the ECC81 fits - I'd expect it to be somewhere between.

 
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Re: Identifying valves with no markings

Post by Terrykc » Tue Nov 20, 2012 6:42 pm

Stephen, so that you know exactly what you are looking for, find any Mullard/Philps valve you have and look for the markings on that.

It is two rows of tiny characters - 3 - 4 per row - just above the base on the side wall.

 
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Re: Identifying valves with no markings

Post by freya » Tue Nov 20, 2012 6:58 pm

Ooops, i did mean the ECC82 had more current, even staring at the post to check details didnt click :oops:


Thanks again
Stephen

 
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Re: Identifying valves with no markings

Post by Terrykc » Tue Nov 20, 2012 11:17 pm

Terrykc wrote:... It is two rows of tiny characters - 3 - 4 per row - just above the base on the side wall ...

Oops! I omitted to say that the codes are etched into the glass and, therefore, permanent!

I'm talking about B7G and B9A, etc., valves here, by the way ...!

 
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Re: Identifying valves with no markings

Post by Ed Dinning » Wed Mar 13, 2013 10:50 pm

Hi Folks, an interesting thread, but my requirements are to ident valves that are at least 30 years older.
The early triodes are fairly easy. Find Vg for cut off, measure u at a sensible Vg and measure Ra. Then cross check with valve data for likely type. It will probably work if simply plugged into an old set, but not as well as the correct type. The difficulty arises for Rf Pens and FC valves, especially vary u types.
Any ideas?

Ed

 
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Re: Identifying valves with no markings

Post by 6.3volts » Sun Apr 21, 2013 1:05 pm

This sometimes works for me with absent markings. Put the valve in the fridge to cool it then breathe on it gently and some will reveal a slight outline of the original marks if the light is just right. Try different light and angles and try several times.

 
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Re: Identifying valves with no markings

Post by crackle » Wed May 01, 2013 9:47 am

I have never tried it but I always wondered if a UV lamp would show any outline of old markings.
Mike

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