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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 28th Oct 2019, 7:05 pm   #1
vintage port
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Smile Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

HI all,
I have some TV valves of the PL family that I want to test. I have an AVO Mk 4 without the right sockets, and I have a B9D socket I can use but don't want to mess with the AVO.

I considered taking an old B9G valve apart but discovered this doesn't work from another thread here.

I have an old B9 socket on the AVO but no B9 valves or bases

Apparently one can use a B9a base but they are all glass I thought? Are there plain paxolin bases with pins that I can use and if so where can I get them, or does anyone have a duff B9 valve they'd be willing to pass my way, or something to trade as I have some nice (and not so nice) old radio valves.

Suggestions please!
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Old 28th Oct 2019, 7:29 pm   #2
G6Tanuki
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

Not familiar with your particular tester but does it have a socket for the B9G valves (EF50, CV309 etc) ??

That would give you the right number of pins - it would be relatively easy to cast (using Araldite or similar) a disc with suitable 'pins' in it to fit the B9G socket, then use a pair of rods also cast into the B9G socket to support a B9D of the type with a pressed-on metal mounting-clamp.

Alas there's no easy way to do the same with 12-pin "Compactrons" of which I have a few.
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Old 28th Oct 2019, 7:31 pm   #3
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

For many years valve base plugs have been used for interconnections, adapter
components and plug in inductors. Here are some;
http://www.partridgeelectronics.co.uk/03Cconnectors.htm
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Old 28th Oct 2019, 9:15 pm   #4
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

Hi G6Tanuki
Yes, it has a B9G socket but I have no experience of casting with Araldite, I fear I'd end up making a terrible mess. Need to google some techniques!
I'd have thought for compactrons you could connect and test one section at a time couldn't you? It would require some kind of (HV) switching arrangement near the valve holder to move connections from pin to pin between tests but possibly do-able?
Thanks Restoration73, Partridge show some B9a base plugs (and other goodies) but the B9a bases aren't in stock sadly, all I have found on eBay is stuff that's already made up. I'll keep looking
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Old 29th Oct 2019, 8:19 pm   #5
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

Quote:
Originally Posted by vintage port View Post
Suggestions please!
Would this be any help?

https://www.ebay.co.uk/itm/9Pin-Bake...IAAOSwaadasxOw
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Old 30th Oct 2019, 12:57 pm   #6
David Simpson
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

Best bet, vp, is to fit a ceramic B9D Magnoval valve holder into a nice big old bakelite base off an old B9 valve. Just about a perfect fit with enough of a wee gap to judiciously araldite together. Reason - PL500's & their kin are a high slope powerful valve - prone to parasitic oscillation at high Ia in unsuspecting valve testers - so fitment of ferrite beads inside the adaptor is essential. An old B9 valve base gives you plenty of room for beads & interconnecting wee leads. Caution - before final aralditing - double check that pin numbers match up & megger for insulation & continuity. Bobs your uncle.
Sadly, I've nothing in my junk box, otherwise I would have sent you what you need. But surely, someone on the Forum has something lying about plus a handful of beads.
In my adaptor, I used 0.5mm ins. flex, and had enough beads with a suitable int.dia. to just fit over the wire's pvc insulation. I also secured them with wee short lengths of heat shrink sleeving - keeps them out of the way whilst soldering between the pins. Originally, the old B9 valve base would have had its thin wires soldered at the end of the hollow pins. Give the old pins a good de-solder & clean.

Regards, David
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Old 31st Oct 2019, 9:26 pm   #7
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

G4EBT, thank you, I have seen those but have no idea about pulling one apart - are they just bolted together? Its an easy way into the B9a socket at least.

David Simpson, thank you as well, what you suggest seems sensible. I have neither a ceramic B9d socket nor a B9 valve to disembowel at all! I have a McMurdo type B9d socket in good nick, I could use that at a pinch, but B9 valves aren't exactly common these days, I've scanned the fleabay job lots and they don't even appear in them In truth I don't know what would be the least valuable common radio valve that i could but fdrom eg. Langrex and just sacrifice for this purpose?

Lastly, thanks again and yes, I was going to ferrite the heck out of the thing
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Old 1st Nov 2019, 11:31 am   #8
David Simpson
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

VP, I'll ask around up here & see if any vintage chums have a gash valve. B9's were used a lot in pre-war radios - triode hexodes & other multi-electrode valves from that era.
If you pop along to one of the BVWS Swapmeets, or get a chum to, surely you'd find one lying in a gash box on a table.

Regards, David
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Old 1st Nov 2019, 12:19 pm   #9
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

Thanks DS, I'd appreciate it, obv. pay postage and as required. Unfortunately I didn't have my brain in gear at the last Audiojumble although there were less old valves around than usual I thought..Otherwise roll on March and the Harpenden meet!
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Old 1st Nov 2019, 3:32 pm   #10
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

Could you not use the ef50 like g6tanuki says, but in a different way?
Cut some of the can off, leaving say 1" or so remaining. It is a really common metal cased valve. Fit your b9d base across the top of a piece of metal or plastic tube then clamp this assembly to the remaining part of ef50 metal tube using a jubilee clip?
The British 9 pin valves are not very common at all, hence even David Simpson needing to ask around for one!
Mind you, I don't know the solderabilty of the internal ef50 pins, having never taken one apart.
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Old 2nd Nov 2019, 4:06 pm   #11
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

Well, I've got some EF50s so I might as well try. Others have failed on this route which is why I haven't gone down it, but I have no idea why failed. A knackered EF50 can't be losing the world too much if I destroy it...I will report back.
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Old 2nd Nov 2019, 4:46 pm   #12
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

I thought the EF50 was a normal glass-envelope valve inside the metal can. And that the pins came through glass-to-metal seals on the envelope. The glass you can see around the pins on the bottom is part of the envelope.

So if you cut the can open you have a normal glass valve inside. OK, you might be able to cut round the envelope and remove it, then cut away the electrodes without destroying the base, but it will not be easy. Nor will making connections to the remains of the pins without cracking the glass.

Silly idea : Make an adapter with an octal plug wired to whichever 8 of the B9D pins are most used. And a flying lead on the last pin going to a plug that you can stick in one of the sockets on the VCM that are used for the top cap lead if you need that last pin.

Last edited by TonyDuell; 2nd Nov 2019 at 4:48 pm. Reason: Had a silly thought.
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Old 2nd Nov 2019, 5:05 pm   #13
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

Looks hopeful - the pins seem to travel reasonably far into the valve internals if this is anything to go by?
https://www.petervis.com/Radios/one-...rge-image.html
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Old 2nd Nov 2019, 6:40 pm   #14
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

I must admit, I have never had one apart, but just thought there may be sufficient metal to use the jubilee clip on.
May be like my late mum used to say "You know what thought done!"
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Old 14th Nov 2019, 8:50 pm   #15
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Default Re: Whats the easiest way to make a B9D adapter for AVO Mk 4 tester?

Update, I took David G4EBT's advice and got a B9a adapter, found a perfectly fitting polypropylene high pressure pipe adapter that fitted both units and set to work. Much araldite later...Well it ain't pretty but it works a treat. I have only tested one as I now have a VCM related issue I hope to fix (see this forum if you feel any urge to help )

100 Ohm ferrites fitted to all the pins (they were the biggest I could fit in the space) and there appears no obvious evidence of oscillation so far. A big thanks to all of you for helping me out! I didn't try the EF50 solution as I wanted to get on with stuff, but one day perhaps I will and will resurrect this thread for an update.

Thank you again!
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