Valve (tube) extender

[mark pirate]

I was watching a youtube video on American TV restoration, and noted that the
guy was using this clever device that plugs in to a valve socket, the valve then plugs in to the base on the top.
There is a ring of contacts round the base enabling readings to be taken without having to remove the chassis.

Were they ever available over here, as I have never seen one before.

Mark

I have just found this link with better photos: http://www.test-and-measurement.net/tube-extenders.htm

[Peter.N.]

I've never seen one either. I have always been able to get to the back of the valve base, could be useful though.

Peter

[Mr Moose]

Hello,

I have a B4 version of a similar thing probably from the 1920s.

in 1932 Avo produced a somewhat more sophisticated version called the AvoDapter which used a flexible connection and allowed current as well as voltage measurements, see here http://www.museumoftechnology.org.uk...d.php?key=1033

Yours, Richard

[mark pirate]

I am surprised that they are so rare, Avo thought it worth doing. I think it would be a useful addition to the workshop, it would save the hassle of removing the chassis and delve deep in to the wiring get to the valve socket.

I am thinking of making a couple out of bits from the junk box, in the words of Jeremy Clarkson, 'How hard can it be'

Mark

[ITAM805]

I knocked a pair of these up for testing EL34/6L6's. They also came in handy for attaching jump leads for testing 'Dalek's'

[mark pirate]

That looks great, your tester looks interesting too. I have found some rigid plastic pipe that is just the right diameter to join a base from a dead octal valve to an octal valve base.
My idea is to drill small holes in the pipe and loop through some rigid copper wire to form 'ears' under each pin on the socket, giving me the option to attach small croc clips or just use a probe to take readings.

A B9A extender could also be made this way if I can find some suitable pipe.

Mark

[G4XWDJim]

Mark,

I have one of the octal versions. I think it came to me 20 odd years ago in a depleted spares kit belonging to an American comms receiver.
On one side it says 'adaptor tube socket' confirming its American roots and on the other it has a number, OCTAL U-102/U which might help identify its origin.

The American Antique Radio forum might be worth asking.

I have a B7G adaptor or more correctly an extender which is often very helpful but without any of the ears you mention. I made a B9A one but needed to make it taller to clear the screening ring and with more pronounced ears to make it easier to aim at.

They are very useful when working on sets that have restricted access to the valveholder bottom.

Jim

[kalee20]

I've never used one, but know they exist, often with shorting links to allow insertion of a current meter.

Limited usefulness at times I reckon - can you imagine using one trying to measure the anode current of an ECC85 in a VHF tuner, under normal operating conditions?

I assume the resistor in the home made version is in the cathode lead (for measuring current and small in value compared to the average cathode resistor), one may be usefull in the screen grid too.

[McMurdo]

I made my own as I repair guitar amplifiers with the EL34/6L6 octal output valves where manual fixed bias has to be set. You can buy ones with a small current shunt for anode current testing but commercially they're a bit dear.
I took an old octal relay and took the insides away, 'dremelled' a hole in the top for an octal base and joined the appropriate top and bottom connections with 20A fuse wire, bringing out the appropriate connections on 2mm studs. Fiddly to make but very useful.

Vintage-wise, Avo's was called the Avodapter, they were also made by Bulgin.

[ronbryan]

I have an Australian made "Swe-Check" B7G valve test adaptor. It is made from Paxolin tube and has seven wire loops to hook a test prod to. No provision for current measurement though.

Ron

[G6Tanuki]

A piece of WWII-era US military gear I worked on came to me two such 'extenders' stacked one on top of the other and fitted to an otherwise-unused Octal valvebase on the chassis. They each had a 10-ohm resistor in one of the pin-circuits - the test spec had you fit one adaptor to each of the modulator-tubes and, then using a test-meter on the 10-ohm resistors in turn set the standing bias for each half.

[I repurposed the spare Octal valve-base to fit a dual-triode so I could use a dynamic mic rather than the original carbon 'growler']

[mark pirate]

Hi Ron, that is more or less how I intend to assemble mine, except using a plastic tube.
I have everything here to build a couple, just need to get some epoxy resin tomorrow.

Mark

[Top Cap]

Taking this idea a bit further I made this bias adjustment box for a stereo push-pull amplifier using four EL34 valves, though the photo shows 6CA7's being adjusted. It's nice to keep an eye on all four of them when testing such amplifiers

[Tractorfan]

Hi,
I knocked together something similar, but it was to allow an EZ80 to be used in place of a missing EZ90 in a French radiogram. It worked a treat as the characteristics of the two were similar. Eventually I found the correct valve in a scrap radio I was given.
Cheers, Pete.