It is currently Fri Jun 23, 2017 1:00 am

B4/B5 to B7G valve base adapters

Valves, Transistors, IC's and Components. Bench test techniques, Test Gear - Valve Testers, Scopes, CRT Testers, Bridges, Sig Gens, Pattern Gens, Workshop tours etc
 
Posts: 201
Joined: Wed Mar 05, 2014 7:52 pm
Location: Lancashire

B4/B5 to B7G valve base adapters

Post by Sparks » Sat Aug 20, 2016 5:07 pm

Useful valve base adapters, vintage to modern.
I find these very useful. They are B7G valv-holders inserted into either B4 of B5 bases taken from defunct 2Volt valves. The centre spigot is removed from the B7G valve-holders. I 6ba threaded spacer is bolted into the base from underneath with a countersunk bolt. The B7G valve-holder is mounted in an acrylic ring that is slightly bigger than the B4 or B5 base. Each adapter has a dropping resistor inserted in the positive filament lead to allow the chosen 1.4V valve to run on the 2 Volts normally required by vintage wireless sets. In the case of the B5 adapter, the centre pin is used, so the B7G valve-holder is secured by two 6ba threaded spacers under the two normal valve-holder securing holes. What would have been the anode cap of a screen grid valve, is taken to a terminal on the side of the B4 base. In the B4 triode adapter, the screen grid of the B7G valve is strapped to the anode, thus running it as a triode.
Bob
Attachments
B4 - B5 to B7G adapters.jpg

 
Posts: 4203
Joined: Wed May 02, 2012 3:35 pm
Location: Worksop

Re: B4/B5 to B7G valve base adapters

Post by Refugee » Sat Aug 20, 2016 11:02 pm

Yes it also works for other valve types.
I did international octal to B9G to fit 6/30L2 in place of ECC33 used in a phase splitter and voltage amplifier.
It made no difference to the sound in spite of some folks spreading myths about octal valve types.

Do have a look in the lounge.
They have found fuses that cost £40 in there and I bet they also make no difference to the sound either.
Attachments
DSCF2398.JPG
DSCF2402.JPG

 
Posts: 201
Joined: Wed Mar 05, 2014 7:52 pm
Location: Lancashire

Re: B4/B5 to B7G valve base adapters

Post by Sparks » Sun Aug 21, 2016 6:48 am

Yes, I looked at the fuses. As far as I am concerned, a fuse is a safety protection device, and I can't see how it would make the slightest difference to the sound, or anything else. It either conducts as a straight wire, or it is "blown" and does not conduct at all! :aaj
The valve adapters are very handy, and I have even made B7G to octal, but it takes longer to make a B7G male plug. It would also be very handy to have an international octal to Mazda octal adapter, as I quite like Mazda octal valves, but dislike their bases!
Bob


Return to In The Workshop



Who is online

Users browsing this forum: No registered users and 2 guests