Mystery radio
 

Had this a while but what is it? Three valves and seemingly no power supply so assuming battery powered.

Attachment 257376Attachment 257377Attachment 257378Attachment 257379Attachment 257380

Re: Mystery radio
 

Three valves, three large coils. Have no interest in restoring it, or keeping it really. Would be better in the hands of someone who likes really vintage stuff but its a curio all the same. I rescued it from a box of junk. It appears to have a printed diagram and component list so doubt its home brew.

Re: Mystery radio
 

Was probably a kit for home build, I would have thought.

Re: Mystery radio
 

Any info at bottom right of the circuit digram?

Re: Mystery radio
 

I would have said homebrew but for that circuit diagram, looks military. Looks well modded though , I must say. Not battery with 6.3 AC and HT written on it.

Re: Mystery radio
 

Some of the parts have Air Ministry marks or numbers on them.

It could be either totally homebrew or alternatively made from modules taken from surplus military equipment.

Re: Mystery radio
 

With the number of controls on the panel, type of coil and tuning capacitors, could it be a transmitter?

John

Re: Mystery radio
 

The drawing seems to be attached to a lid or panel that has been repurposed. into a home brew.

You can see where part of the drawing and paint has been crudely scraped away to make an electrical connection with a bracket.

The component on the lid seems to be marked 10/1523

All in all a bit of fun for someone to play with :thumbsup:

Cheers

Mike T

Re: Mystery radio
 

Will post some more pics asap.

Re: Mystery radio
 

The parts list shows parts with RAF store numbers. Something home made using some RAF metalwork.
Mike.

Re: Mystery radio
 

Can't get to bottom of diagram but heres some more photos.

Attachment 257416Attachment 257417Attachment 257418Attachment 257419Attachment 257420

Re: Mystery radio
 

I might have a go at restoring it if I actually knew what it was. If transmitter I won't bother. May just strip it for its parts and make some steampunk thing out of it.

Re: Mystery radio
 

Looks more like a homebrew 1V1 TRF receiver to me, heavily screened RF stage and with what looks like perhaps preset and bandspread tuning for each tuned circuit In the post war era there was tons of ex military gear advertised in magazines that you could buy for very little and strip for the chassis and components. Bardwells here in Sheffield still had odd bits of it 'when I were a lad' in the late 60's/early 70's. There's a big hole in the chassis partly covered by other components which says it's not a professional build. As for the circuit, it's possibly a 'blueprint' that radio mags in the 50's were fond of publishing. I agree it looks kind of military except that I'd expect to see component designations like R1A, C2A etc. Very interesting!

Re: Mystery radio
 

What is the tube lineup?
I saw a VR65, IIRC that is a voltage regulator, without looking it up.
Quite uncommon in a HB receiver.
That, the number of variable caps, and the big coil tend to make me think it is a HB transmitter.

Re: Mystery radio
 

The two variable capacitors in Post 1 photo 2 above appear about the same value and are in parallel. They are brought out to separate knobs on the front panel? Rather a strange arrangement.
Can you trace out the circuit? The VR65 is equivalent to the SP61 (see http://www.r-type.org/exhib/aaf0004.htm). A sketch of the circuit, even if incomplete, would offer some clues.
Peter

Re: Mystery radio
 

Other two valves

Attachment 257549

The VR65 ia a WWII military receiving pentode valve made for the RAF. I think it would be very difficult to trace out the circuit.

Re: Mystery radio
 

VR65 (receiving pentode) - http://www.r-type.org/exhib/aaf0004.htm
1 2 3 4 5 6 7 8 TC
h k a g2 g3 m nc g1
What connects to the anode (pin 3) - g1 (top cap) g2 (pin 4) etc. ?

EL33 (audio output valve) - http://www.r-type.org/exhib/aad0112.htm
1 2 3 4 5 6 7 8
m h a g2 g1 - h k
Likewise, what is connected to the anode pin (3)? The control grid g1 pin (5) etc.

Where are other components connected that are not directly connected to a valve base? TRF receivers, oscillators and transmitters have distinctive circuitry that can help to identify what you are dealing with here.

Peter G3PIJ

Re: Mystery radio
 

Heavily got at, looking at the mixture of knobs. Still think that circuit is military though.

Re: Mystery radio
 

The pictorial circuit that can be seen in photos 2 and 3 of Post 11 includes components mounted on tagstrips; also a coil with tapping lugs (L2, L3, L9) down the side. This does not coincide with the actual layout of the components in the other photos, so I suspect that this pictorial circuit is simply whatever happened to be glued to the piece of metal that was used as the front panel. It's looking to me like a straight receiver built from whatever came to hand by someone who was not a radio technician. It might even not have worked!
Peter

Re: Mystery radio
 

Certainly short wave anyway.