B9A Breakout Box

[jonmiller]

Just finished this, and yet to try.

[ms660]

If that's a home brew job I'm well impressed, if home brew what's the trick to getting the neat lettering/numbers?

Lawrence.

[jonmiller]

I have a CNC flat bed router, and can engrave panels.

[ms660]

Very handy, looks real pro.

Lawrence.

[jonmiller]

Thank you Lawrence, if it works well, I will do one for Octals.

[Skywave]

As that is a 'break-out' box, am I correct in assuming that beneath the socket shown in the photo there is a B9A plug - which is fitted into a B9A socket on a chassis - and then the valve is plugged into the 'break-out' box socket?

Al.

[jonmiller]

Hello
There is a flying lead with a B9A solder plug on the end as per picture. So you just plug it into the valve socket.

[AC/HL]

They used to be popular in the early days, I think they were also commercially available back then.

[frankmcvey]

Beautiful work, Jon.

Sure, they were available commercially in the '20s. I recollect seeing an old advert for just such a breakout adaptor - it was cylindrical and had solid brass bars connecting the pins at the bottom to the sockets on the top - these were radially arranged around the outside of the adaptor, Squirrel-Cage-fashion, and voltage readings could easily be taken. However, the clever bit was that the bars were held in place by by screws top and bottom, so that any of the connections into the valve could easily be broken into by unscrewing a bar. By replacing it with a milliammeter, one could also measure the current flowing through any particular valve electrode without disconnecting any of the equipment's internal circuitry.

The diameter of the break-out "box" was similar to that of the valve, so there were no access problems.

I'll try to find the picture and post it - perhaps it might inspire an upgrade for Jon's forthcoming Octal Breakout Box!

[emeritus]

A very nice job indeed. Bulgin used to make a range of such adaptors, called "split adaptors": extract from their 1937-8 catalogue attached.

[Mr Moose]

Hello,
In the 1930s Avo produced a similar device called the AvoDapter.
The basic version was for B4, B5 and B7 based valves but there was the optional extra AvoCoupler for B9 based valves.
There was a plug that plugged into the valveholder, with a crocodile clip for the top cap, connected by a multicore cable to a valve panel with terminals.
It also has a switch to break some of the connections so current measurements could be made.
There is a picture here http://www.museumoftechnology.org.uk...d.php?key=1033
Yours, Richard

[jonmiller]

Thank you all for the kind comments and further information. Its interesting to see that the Avodapter was 25 Shillings in 1923, which works out to approx £63 in todays money (using a purchasing power calculator).

[russell_w_b]

Very nice indeed. Much nicer than the ones I knocked up to work on my RA17!

[jonmiller]

Hi Russel
Thank you for the kind comments,Yours have more functionality than mine though, with another Connblock in there you could break into the lines for measuring current as per the post above describing some of the Bulgin models.

Kind regards

Jonathan

[russell_w_b]

Originally Posted by jonmiller

Hi Russel
Thank you for the kind comments,Yours have more functionality than mine though...

I was tempted to make a version like yours (minus the lovely lettering and finish!), and have seen similar designs on audio websites, but yes: I can break the circuit and slip in a multimeter to measure currents if necessary.

I gather from the Racal RA17 manual that a short 'pillar' type stand-off was used, raising the valve sufficiently to get to the terminals, and which might be better at reducing pick-up than my arrangement. I didn't use screened cable on mine, which perhaps I ought have done

[Skywave]

Does anyone know, please, from where I can obtain the B9A plugs as featured in this thread?

Al. / Aug. 7th. //

[ms660]

Not sure if they are available at a reasonable price these days Al.

It might be possible to make them....PCB style B9A valve socket, then solder a 1.02 mm double ended Vero pin into each socket on the valve base, just and idea.

Lawrence.

[russell_w_b]

I got mine at 'Electrojumble', Al. They're 'Cinch' plugs.

[ms660]

Just another idea....bare B9A PCB "blanks" are available on Ebay, they are pre drilled and so far as I can tell will take 1mm solder pins (single ended/double ended/Vero or whatever)

They are 31mm in diameter but I'm guessing they could be turned to a smaller diameter.

Double ended pins could be inserted in one and secured at the rear with a dab of epoxy, another blank could then be glued on then wire connections made to whatever is left poking out, then shrink sleeve or whatever.

I hope this makes sense.

Lawrence.

[Herald1360]

Depends how many you need. I've got a couple lurking somewhere with no use for them.

Back to original post- you could also use that with the plug safely in a box, for connecting a valve to PSUs for valve testing purposes using a bunch of banana leads.