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Old 15th Sep 2020, 6:17 pm   #1
David Simpson
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Default 9 Pin Interconnector Plug

I'm wrapping up my Roberts Valve Tester project. As its finished & working great. One annoying & outstanding query is the interconnector lead & its plugs. (see RVT Post 12).
Measured across the outer pin edge radius - an IO plug is 25/32" or 20mm, an MO is 26/32" or 21mm, approx. and this plug falls between the two. Instead of a bakelite spigot it has an aluminium blade 8mm wide & 2mm thick by 15mm long. The wee nick in the blade is orientated between pins 1 & 9.
I've scrolled & scrolled through internet pictures of similar vintage plugs, but nothing matches. An Amphenol & a McMurdo looked something similar, but no "Blade".
If I'm to make the full compliment of valve holder adaptors, I'll need 8 matching 9 pin f/m sockets. And, identify them for my lengthy "Write - Up".
Any help or advice most appreciated. (And, apologies for photo quality).

Regards, David
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Old 15th Sep 2020, 7:27 pm   #2
turretslug
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Default Re: 9 Pin Interconnector Plug

I wonder if it would be acceptable to make use of some sort of arrangement with 11-pin relay sockets and cannIbalised relay bases (same diameter as IO)?

Hope I'm not teaching you to suck eggs David, I know you've plenty of this sort of stuff under your belt and filed in the grey matter, but I've seen those metal tangs used on IO plugs simply as a substitute for the usual moulded spigot when the base is Paxolin, rather than Bakelite- the cutaway tang enables quick central location in the socket, the part between 1 and 8 (or 9 here) goes in the usual keyway. Thrifting, as opposed to anything clever or different! 9-pin "IO" type, that is new to me though,

Colin
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Old 15th Sep 2020, 8:50 pm   #3
David Simpson
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Default Re: 9 Pin Interconnector Plug

Right enough, Colin, it might come to that. Making up adaptors with a larger pin configuration, if I can't acquire any of the 9 pin females I need. I've one or two of those 10 or 11 pin relay plug & sockets, but wouldn't be surprised if they weren't just as rare & elusive.
The missing male adaptors are:- B7G, B9A, B9G, SM4, SM5, B8G & B8A. Quite frankly, I don't think I'll be testing many SM4's or 5's, but definitely the others.
I've made up a number of adaptors over the years :- Septar, B9D magnoval, B8B, UX7, using either IO or B9 Plugs, plus B4 to Cruciform. However, it would seem that I'm stuck with this 9 Pin kit which came with the old Roberts valve tester.
Its possible that the London Sound Labs, who made the Roberts not long after WW2, might have used ex WD or ex US connectors which were in plentiful supply from surplus equipment.
If I'm to recommend to other valve testing folk to consider making their own "In situ" valve tester, they would also need to source a couple of males & a number of 9 Pin(or 10 pin, or whatever) females for their interconnector set-up.

Regards, David
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Old 15th Sep 2020, 9:36 pm   #4
Ed_Dinning
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Default Re: 9 Pin Interconnector Plug

Hi David, I've seen a few of the plugs with "blade " spigots before, used as interconnects on some 60's TV's and may even have the odd one, but I cant remember ever seeing the female socket (B9G perhaps?)

If your work is to be copied after the write up, you could suggest some of the modern round or square plastic "consumer" types that are low cost and robust. Mil circular screw types would look nice but would need deep pockets!

Ed
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Old 16th Sep 2020, 6:58 am   #5
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Default Re: 9 Pin Interconnector Plug

Sorry, can't help with your query David, though they look to me like the sort of plugs used in broadcast or lighting type applications. Re 11pin relay sockets; I've a small draw full of 11pin relay sockets bought on ebay a while back, I think RS still do them. I also have 11pin male jacks with a box fitted, not sure what they were intended for, sort of project box with 11pin male fitted. Omron still make 11pin relay's AFAIK too. All this rambling means that 11pin relay sockets etc should be relatively easy to procure.

One last thing though, someone used relay sockets on an amp build and had trouble with parasitic oscillation, I've had similar issues too, a point worth bearing in mind if using then in a tester.

Andy.
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Old 16th Sep 2020, 11:34 am   #6
David Simpson
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Default Re: 9 Pin Interconnector Plug

Right enough Ed, a more modern design of 9 way interconnection lead/plug/socket would be the way forward for a modern copy of the Roberts "in-situ" design. Its just that, as you ken, I've now got a reasonaby decent collection of adaptor plugs(thank you), so will make do meantime. Whilst still trying to locate a source of female 9pin sockets.
Maybe you remember that the f/m socket in question was in the very top left of the Roberts' valve holder panel, whilst the B9G was several inches away - having a greater pin outer diameter(nigh-on 26mm).
Aye Andy, parasitic oscillation was a major thought from the very start of the project, hence the fitment of "Ferrites" to the new 10 wire "loom" to the valve holder panel & T/C terminal.
Digressing slightly, but due to a miss-order, I've heaps of "clip-on" ferrites spare.

Regards, David
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Old 16th Sep 2020, 11:40 am   #7
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Default Re: 9 Pin Interconnector Plug

I looked at that plug with the 'blade' type centre pin and didn't give it a second thought, thinking it was a cheapie way to get round having to mould a proper octal type spigot. I thought it was designed to go into something like an octal spigot hole in only one orientation Got that wrong!

I suppose the last thing they'd want to use would be a standard valve socket, else soom fool would soon shove a valve straight in it.

David
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