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Old 1st Sep 2018, 9:17 pm   #1
David Simpson
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Default Vintage BBC Valve Testers

chriswood1900 & ms660, aka Chris & Lawrence, have today just submitted posts about BBC Valve Testers to ukol's, aka Colin, thread in Components & Circuits regarding Thermionic Valve Emission. Extremely interesting links regarding a BBC Valve Tester Panel VT/4 & a later Valve Tester VT/5.
Maybe I should've gone to Specsavers more often in the last ten years or more since joining the VRR&R Forum - but they're news to me Forum-wise, and many other valve testing enthusiasts I imagine. Nor have I seen anything about them in the BVWS's Bulletin or VMARS's Signal Magazine. Perhaps they're mentioned somewhere in old Radiophile or Radio Bygones Magazines ?
Anyway, the BBC documentation is a Must Read, particularly for those with current threads about Valve Testers & Valve's electrodes & emissions, etc.
So, the question is - who has got one of these BBC pieces of equipment ? Or has other documentation or pictures ? God, I hope the BBC didn't dump heaps of these items & documents in landfill years ago, after the war !

Regards, David
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Old 1st Sep 2018, 9:33 pm   #2
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Default Re: Vintage BBC Valve Testers

I don't recall ever seeing any reference to these testers before!

Andy
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Old 2nd Sep 2018, 11:40 am   #3
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Default Re: Vintage BBC Valve Testers

Googling "Vintage BBC Valve Testers" resulted in two great finds :- Firstly a Forum thread by John BS back on 31st October 2015 titled "BBC 1940's equipment: valve-tester etc". In which he mentions the VT/5, and other Forum folk mooted the idea of collaboration with AVO. My only excuse for not seeing it(apart from a "Specsavers" experience) was the fact that the shooting season had just started - an exiting time.
Secondly - a great article in the BVWS Bulletin Vol24 No4 Winter 2001 by Denis Tabor titled "Valve Testers". Back then I had no thoughts of vintage radio/electronics pursuits, so wasn't a BVWS member. Denis Tabor's extensive article is a Must Read for any folk with an interest in Valves & Valve Testers.
Please, particularly ex BBC folk - scour your attics, sheds, shacks, etc. (and your minds) for any bits & bobs off old BBC valve testers or documentation.
Is Denis Tabor still on the go, I wonder ? What a really interesting guy.

Regards, David
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Old 2nd Sep 2018, 4:56 pm   #4
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Default Re: Vintage BBC Valve Testers

David thanks for the reminder about John BS it was a useful read in the context of this tread. I originally stumbled on the BBC information whilst looking up some info on a valve I found in a job lot I bought at RWB a couple of years back which was marked BBC B4 and Google took me to the article on Valve testing in my earlier post, hence I did not look further at the other info that Lawrence found on the VT4 and 5. It would be great if we could turn up more info or an example of one.
Small correction the BVWS article was Vol 26 No4 from page 7 on.
Regards
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Old 2nd Sep 2018, 6:53 pm   #5
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Default Re: Vintage BBC Valve Testers

Hi David, I believe Denis and his wife are still alive and well, albeit getting on now. I normally exchange Xmas cards with them.
Denis sold off his collection few years ago and it was pretty extensive.
Hopefully he may still have some memories or documentation of them.

I'll PM you his address if I can find it

Ed
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Old 3rd Sep 2018, 10:37 am   #6
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Default Re: Vintage BBC Valve Testers

Not sure if this helps but the manuals are here: http://www.bbceng.info/ti/aco-post-1960.htm
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Old 3rd Sep 2018, 12:51 pm   #7
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Default Re: Vintage BBC Valve Testers

Hi,
I found some where, 2-years ago, an similar 13 pages (7,5MB) VT4 description, but that is not the same! If somebody wish it-pm me please...
Regards, Karl
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Old 5th Sep 2018, 12:41 pm   #8
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Default Re: Vintage BBC Valve Testers

Many thanks guys for replies so far. Most appreciated. Before I let my enthusiasm gets me banging-on too much(as usual), I'm taking things steady & pursuing a couple of leads.
Mind you, having read the BBC info in the link for VT/5, they clearly state in the paragraph beneath Fig. iv. regarding "gm Tests for Multi-electrode Valves" - - "(It should be understood that this current bears no direct relation to the current which would obtained by the application of a comparable d.c. voltage, and cannot be regarded as the Ea - Ia characteristic of the valve)", when talking about the half sinewave peak Ia produced by their AC circuitry. Just like AVO & their heffing (AC) VCM's & Testers, and other makes of testers. This BBC statement is akin to what I've being advocating for some time now. AVO & the others just haven't explained the phenomenon clearly, or at all. Hence some folk's problems with modern DMM's & so on. (RMS, root2, & so on)

Regards, David
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Old 5th Sep 2018, 5:20 pm   #9
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Default Re: Vintage BBC Valve Testers

Do we have a year when the BBC VT/5 was made, or the instructions written? The VT/4 states 1939 in the VT/4 document below but the second document that covers bot the VT/4 and VT/5 doesn't have any date, at least I can't find any.

Link to VT/4 document: VT/4 and to VT/5 document: VT/5 found in the thread Thermionic Valve Emission.

Reading the text for the VT/5 and comparing it to the AVO patents it looks like it was written sometime between the two patents AVO acquired (GB480752 - 1938 and GB606707 - 1948) for their method of testing valves under AC conditions, but that's just my guess - having a correct date would be very good. The VT/4 document is written one year after AVO acquired their patent.

Link to the two AVO patents in this post: AVO GB606707 and GB480752 patents.

My guess is that the BBC VT/5 text was written before AVO had its GB606707 patent accepted so that the portion with the Ea-Ia curve wasn't understood fully under AC conditions at that time and therefore not incorporated into the VT/5 design.

Many years ago when I requested material from the IET in London I got some scanned photos and texts which I discarded as they didn't have anything to do with the AVOs I was collecting materials on - however they looked a lot like the VT/4 and VT/5 and as far as I remember they were named "Valve Tester Panels" and not anything like the AVO named their products - maybe someone can look that up again. The IET said that they had a lot of material that was uncatalogued and some in the incorrect places so it won't be easy to find these unless someone has lot of time to spend searching the archives. Since these documents were found together with the AVO documents I bet my money on that there was a lot of collaboration between AVO and BBC regarding the valve testers, and probably on other instruments too.

I always keep this document on AC, DC, Mean DC and RMS voltages/currents and their relationships at hand when I delve into valve tester discussions: Yokogawa BULL DMM Glossary as it has simple descriptions of the terms used and also of the equations and a table that shows the relationships.
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Old 5th Sep 2018, 6:29 pm   #10
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Default Re: Vintage BBC Valve Testers

Right enough, that glossary is more or less those of us with formal electronics qualifications were taught many years back. It'll certainly help many folk with less of an understanding.
Good of you to give us a lead to the IET archives. As a member, I'll get in touch with them & see what can be found.

Tak, min Ven, David
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Old 5th Sep 2018, 9:12 pm   #11
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Default Re: Vintage BBC Valve Testers

Quote:
Originally Posted by Dekatron View Post
I always keep this document on AC, DC, Mean DC and RMS voltages/currents and their relationships at hand when I delve into valve tester discussions: Yokogawa BULL DMM Glossary as it has simple descriptions of the terms used and also of the equations and a table that shows the relationships.
Martin, table 1 in that reference is a bit iffy!

Iasse that the horizontal lines drawn across each waveform represents the zero voltage level. This has to be so for the RMS of the full sinewave to be 0.707 (presumably 0.707og the peak value).... then the mean value is rather questionable, the mean taken over a large number of cycles, or over an integer number of cycles should be 0v. 0.637 is the mean of a full-wave rectified sinewave (again averaged over an integer number of cycles, or rather a lot of them) and that figure reappears in its proper place as the mean of the full wave rectified waveform.

David
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Old 5th Sep 2018, 9:31 pm   #12
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Default Re: Vintage BBC Valve Testers

Hi Martin, there is the UK patent office library, in Lincolns Inn in London. They may be able to help with full details of the patent.
As a young engineer I would do quite a bit of research in there, not sure if access is so easy these days, but it may even be on line now.
Perhaps one of the forum members in the area could check for you.

Cheers, Ed
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Old 5th Sep 2018, 10:17 pm   #13
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Default Re: Vintage BBC Valve Testers

From the points of view of the Forum family- I guess us old qualified guys relate back to the maths & the physics we were taught many years ago, and just accept, as a matter of course, RMS, P - P, root2, pi, & so on. Then on the other hand - younger & perhaps less qualified folk get jolly confused by it all. I suppose in the long run, all that matters is that our treasured VCM's work reasonably well for their age. In the case of these two BBC testers - that age is considerable. I'd dearly love to get my hands on an old wreck of one & restore it. Even if its just a box of bits. The VT/4 came out in 1939 - the same year that Cossor brought out their 3339 Oscillograph. The one I restored was a complete wreck.

Regards, David
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Old 9th Sep 2018, 5:25 pm   #14
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Default Re: Vintage BBC Valve Testers

Seemingly a chap called Roger Beckwith runs a website called "Old BBC Broadcasting Equipment & Memories". There is a "Contact" link, but I cant access it, as I just use good old "Internet Explorer" & Hotmail(Outlook). Yes, I've tried right-clicking & then accessing "paste", but my computer just wont do it. All I need is his email address. Can anyone help, please ? Then I can pick his brains about VT/4's & VT/5's.

Regards, David
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Old 9th Sep 2018, 5:48 pm   #15
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Default Re: Vintage BBC Valve Testers

David you have a PM with his email address.
Regards
Chris
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Old 9th Sep 2018, 10:46 pm   #16
David Simpson
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Default Re: Vintage BBC Valve Testers

Chris & StationX have both kindly sent me the same email info. So have managed to send a message to Roger Beckwith, but no reply yet.

Regards, David
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Old 11th Sep 2018, 3:51 pm   #17
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Roger Beckwith has replied & kindly passed on my email query to ex engineer contacts he knows. As his BBC background was in production. That BBC related website I mentioned a couple of days back, which he runs, is of great credit to him, and well worth looking at.

Regards, David
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Old 11th Sep 2018, 4:40 pm   #18
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Default Re: Vintage BBC Valve Testers

I forgot this one, a mutual conductance standard for checking the VT/4 calibration:

http://downloads.bbc.co.uk/rd/pubs/reports/1938-27.pdf

Lawrence.
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Old 11th Sep 2018, 8:35 pm   #19
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Default Re: Vintage BBC Valve Testers

This was a really interesting document, now I have something to think about!

Converting this to a modern standard with modern tubes or semiconductors will be a nice project.

Thye speak of a patent, you don't happen to know which?

/Martin
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Last edited by Dekatron; 11th Sep 2018 at 8:36 pm. Reason: Forgot to ask about patent!
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Old 11th Sep 2018, 8:42 pm   #20
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Default Re: Vintage BBC Valve Testers

Martin, I don't have any knowledge of any patent but to be honest I've not investigated that avenue yet, if I did I would be restricted to Google searching.

Lawrence.
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