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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 11th Jun 2016, 4:49 pm   #1
G4_Pete
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Default Valve insertion force

I have just recieved some new manufactured ceramic B9A valve bases and was astonished at the force required to insert a valve into it. (with gloves) I then removed all the pins from the socket to check them individually and with valve mounted on cork on a kitchen scales found that some pins needed from 1.5Kg to 2.8Kg to push them onto the pins sliding force being slightly less once started. So selecting an arbritary average of 2Kg that would need 18Kg of force!! I know that you can wriggle the valve around to get it started but even that seemed a problem as the lead in taper is not good and some pins just refused to start with the force I was prepared to use.

That might be good for holding valves in place in guitar amps that are being gigged around the country but for my humble Bush VHF90 it all seemed a bit excessive and anyway I shall now go for a pin swap after reading that trick on this board!

Was there ever a specification for valve insertion force as the above seems excessive.
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Old 11th Jun 2016, 7:55 pm   #2
Jeremy M0RVB
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Default Re: Valve insertion force

There are specs for everything - BS448 gives info for B9A. It lists the minimum insertion and withdrawal force as 1.36kg and maximum as 5.9kg.

It also gives a higher figure for 'as received' (new?) valve holders as a max of 6.8kg

These figures are for a measurement gauge which has all 9 pins fitted, so total force required per valve.

Jeremy
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Old 11th Jun 2016, 9:07 pm   #3
ITAM805
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Default Re: Valve insertion force

Just this week I repaired a Fender Supersonic, to remove the valves for test I had to wear gardening gloves, such was the force needed to remove them from their shielded sockets ! Quite ridiculous and unnecessary amount of grip on the pins
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Old 12th Jun 2016, 1:20 pm   #4
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Default Re: Valve insertion force

Quote:
such was the force needed to remove them
Ah, the thread is about insertion force as was most of the valve data sheets (if not all). I guess 'back in the day' extraction force didn't matter as the valve was duff (or at least charged for as duff) and it broke.
 
Old 12th Jun 2016, 7:36 pm   #5
ionburn
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Default Re: Valve insertion force

I have noticed this as well! I know valves are tough but I almost expect the worst at times.

In these days of zero insertion force sockets for IC's I wonder if the same was ever considered for valves
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Old 12th Jun 2016, 9:11 pm   #6
bikerhifinut
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Default Re: Valve insertion force

Interesting.
I have built a couple of kit valve amps and the advice I was given was to insert an old valve into the brand new ceramic sockets to "ease" them before risking a valuable new one. They do seem to get looser with use. I wonder if it's because so many ceramic sockets have very small holes for the pins and dont have the conventional "blade" style contacts?

A.
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Old 12th Jun 2016, 9:33 pm   #7
G8HQP Dave
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Default Re: Valve insertion force

In an ideal world a Trading Standards officer would feel the collar of someone importing 'B9A' holders (presumably from China?) which do not accord with the British B9A specification. We do not live in an ideal world.

New octal holders can be stiffer than B9A - and octal valves can be more fragile and more expensive!

Fortunately NOS valve holders are still available.
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Old 12th Jun 2016, 9:49 pm   #8
ms660
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Default Re: Valve insertion force

Old octal valve holders can be as well, at least in my old R1155

Were zero insertion valve holders ever devised/made, y'know open them up with a key or whatever, insert valve the turn key or whatever to tighten the sockets up?

Lawrence.
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Old 12th Jun 2016, 11:52 pm   #9
AC/HL
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Default Re: Valve insertion force

Radiospares used to sell an extractor, for B9A valves at least, combined with a pin straightener. Mine is long lost, it was a rubber-like sheath to grip the glass envelope safely.
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Old 13th Jun 2016, 9:55 am   #10
TonyDuell
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Default Re: Valve insertion force

Home Radio (Mitcham) used to sell that extractor too. It had pin straigheners for B9A and B7G on the 'handle' and a rubber sheath on the end to put over the valve and pull it out. I remember the catalogue pointing out it was 'also ideal for removing B8A valves'. I think it was made by Belling-Lee.

Many years ago I found one in the '5p' box at Home Radio. It still lives in my toolbox.
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Old 13th Jun 2016, 11:17 am   #11
m0cemdave
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Default Re: Valve insertion force

Those extractors are very useful.
Mine is light blue in colour, and labelled as a Belling-Lee L.1424
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Old 15th Jun 2016, 10:48 am   #12
G6Tanuki
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Default Re: Valve insertion force

Quote:
Originally Posted by pwdrive View Post
Were zero insertion valve holders ever devised/made, y'know open them up with a key or whatever, insert valve the turn key or whatever to tighten the sockets up?
Some early "professional" US valves (used in things like telephone repeater-amplifiers) used a sort-of zero-insertion-force socket: you put the valve in then rotated it about 15 degrees to make contact between the pins and the socket-springs, a bit like GU10 halogen bulbs do these days. So there was no force to 'insert' the valve into its socket, ony rotational force to make the electrical contact.

There was also a very early proto-version of the EF50 which fitted into its socket with hooked pins, again requiring a twist. Unfortunately this design stressed the glass-metal seal of the pins and was very soon abandoned.
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