1930's radio ID and Dubilier capacitor

[coopzone]

Another strange one for the case files.

See pictures

I have an old radio 2 valve (one unmarked) the other says it's a VP2 (but the base looks nothing like the one I have found online) I suspect someone has re-based the valve, but they must have done a really good job - no sign of glue or anything, except the base once had a centre pin than has now been cut off.

I am also pretty sure it's not the original circuit. I can't find any info for it. I have reverse engineered the current circuit (see pictures).

So can anyone help id any part of the following for me:

Capacitors "Dubilier mica type 610" value?
The type of VP2 valve?
The unknown valve?
The company "Pulford Bros Ltd"
A circuit? Of the original (yeh right like thats gonna happen!)
Any id on the radio ?

Thanks

coop

[Boater Sam]

The capacitor should be measurable, if it's the grid coupler it's probably 0.001uf at most. It's likely to be OK!
VP2 is a trick valve, it's a pentode but now has insufficient pins!
2 grids must be connected together?
Circuit as is looks workable.
Unmarked valve, just about any 2v triode will do. LP2? Have you breathed on it all over looking for a #?

Where did you get the Pulford Bros from? I think they may have been parts makers only.

[ukcol]

I agree that is a bit odd, a 4 pin VP2.

Perhaps the suppressor grid, metalizing and one end of the filament all go to one pin?

That would leave the other 3 pins and the top cap for - anode, screen grid, control grid and the other end of the filament.

[ms660]

The early VP4 was B5 but changed later to B7.

Lawrence.

[Boater Sam]

Yes, it was but this has had its centre pin cut? off. Is there a connection in the socket for the centre pin?
There are quite a number of valves that appeared in B5 and B7 base, and some B9 and B7s too.

[Cobaltblue]

I can think of several sets that used this oval cut out amongst them PYE, Burndept and Red Star

The PYE https://www.radiomuseum.org/r/pye_830_2.html I am thinking of the two decorative panels are empty behind. contain space for batteries.

The lack of symmetry tends to suggest yours home made, kit set or modified commercial set.

Cabinets with that oval style cut out were popular for the home build market.

Cheers

Mike T

[ms660]

The original front end valve might have been a tetrode with a B4 base.

Lawrence.

[Cobaltblue]

The CV171 which is given as an equivalent to the 210VPT which is given as an equivalent to the VP2 was in a 4 pin base with top cap so I guess its possible that's how the original VP2 was configured.

http://www.tubecollector.org/cv171.htm

Tenuous perhaps

Cheers

Mike T

[coopzone]

I forgot one photo before, it's where the name came from. see attached.

I think the valve no.1 is probably a make up version, maybe I'll unsolder the pins and work out what they did with the other grid?

As you do; I connected it to a PSU for a quick try. The output of the triode drives a pair of headphones ok. it seems to run quite nicely.

However the first valve the RF stage is super ropy! the base is either duff or water they did to the original valve is broken, the heater sometimes connects and then disconnects anode current is not measurable at present - I have to get the heater sorted first.

I suspect the theory about it being a kit is correct, it looks like the wires have been re-done at least 3 times over the years. I was told it was last working during ww2 - someone apparently "got it going" due to a shortage of equipment around then.

Maybe later in the week.

coop

[coopzone]

Also forgot to say, the centre pin thats cut off does not have a corresponding connection on the base.

[Boater Sam]

Ah, so the first valve was a tetrode at best, possibly a triode also? On a B4 base + top cap My Lotus used a S22 screened grid tetrode.
VP2 is an impostor, possibly cleverly modified. Cute.

[Boater Sam]

I knew Whitechapel Rd rang a bell, it was the home of Nems Records, prop. Brian Epstein. A famous road in Liverpool.
It's possible that Beaver Radio had something to do with this set, they were in the same road 90+ years ago.

[ms660]

The base on the output valve looks like those used on some Marconi valves, is there a key on the side of the base?

Lawrence.

[G0HFCFrank]

Graces Guide says this about Pulfords;


PULFORD BROS., Ltd., 106-8-10, Whitechapel, Liverpool. T. A.: "Personal." T. N. 1495, 1496 and 1497 Royal. Registered September 8, 1899. Capital £6,000. Employees: 6o. Man_ Director: Egerton Goolden Pulford, A.M.I.E.E. Director: Elizabeth Pulford. Sec.: A. T. Hillman. Products.—Electrical accessories, motor car accessories, electrical and motor car engineering.

so it may have been supplied as a radio or a kit?

Frank C.

[coopzone]

This valve has no key on the side, but I have seen this on other valves too.

Just by way of an update, I have clean the holder (stripped it and used servers and a light brush over with wire wool). Also clean the base of the valve. Powered it back up and it looks good. I can get a "whistle" feed back if I turn the 100pf cap to full on. I have no antenna to test it properly yet.

So so far I have test both valves on an individual basis, both seem to work. Now I need to build a proper power supply. Since the one I have is lashed up on breadboard, and does not have enough capacity to power both valves together.

I wasn't planning on doing this - the idea was to get rid of it not fix it! The other half is not a happy bunny!

coop

[Boom]

Not that it will help but Pulford Bros are listed here from 1938.

https://www.thegazette.co.uk/London/.../7441/data.pdf