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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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11th Jun 2016, 4:49 pm | #1 |
Hexode
Join Date: Feb 2014
Location: Southampton, Hampshire, UK.
Posts: 419
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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. |
11th Jun 2016, 7:55 pm | #2 |
Hexode
Join Date: Jul 2003
Location: Leeds, West Yorkshire, UK.
Posts: 455
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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 |
11th Jun 2016, 9:07 pm | #3 |
Nonode
Join Date: Jul 2010
Location: Folkestone, Kent, UK.
Posts: 2,172
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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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12th Jun 2016, 1:20 pm | #4 | |
Guest
Posts: n/a
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Re: Valve insertion force
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12th Jun 2016, 7:36 pm | #5 |
Heptode
Join Date: Dec 2014
Location: Lincoln, Lincolnshire, UK.
Posts: 583
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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 |
12th Jun 2016, 9:11 pm | #6 |
Octode
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,993
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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. |
12th Jun 2016, 9:33 pm | #7 |
Rest in Peace
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,872
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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. |
12th Jun 2016, 9:49 pm | #8 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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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. |
12th Jun 2016, 11:52 pm | #9 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,637
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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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13th Jun 2016, 9:55 am | #10 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,188
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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. |
13th Jun 2016, 11:17 am | #11 |
Octode
Join Date: Feb 2009
Location: Bletchley, Buckinghamshire, UK.
Posts: 1,205
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Re: Valve insertion force
Those extractors are very useful.
Mine is light blue in colour, and labelled as a Belling-Lee L.1424 |
15th Jun 2016, 10:48 am | #12 | |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,951
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Re: Valve insertion force
Quote:
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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