Marconiphone Type 61 information

[Uncle Bulgaria]

Hello all,

My brother's been given one of these and I wondered what the opinion was. I presume it's a radio receiver, but online information seems limited to a single page from the 'History of Science Museum' with an Oxford University URL.

In his words he 'doesn't want another five year expensive project...' but has no idea what it would take to get it working, or if when working it will be of any use in the modern radio environment! Like me he prefers using old things as he's not got the space nor inclination to be a museum. I've not seen it myself beyond these pictures he's sent me.

With it was a Wavemeter, and this "Radioshack 1000 Channel Pro - 2042".

Any opinions?

[ms660]

There's a magazine article about the Marconiphone here, starting on mag. page 245:

https://worldradiohistory.com/UK/Wir...ld-1928-03.pdf

Lawrence.

[Uncle Bulgaria]

Thank you, Lawrence. What a fascinating article! I had no idea tuning the radio required such effort. The technical aspects of radio reception are over my head as I've only dealt with audio, though I have a vague appreciation that it's to do with resonant circuits reacting to the frequency of the particular broadcast.

All the valves appear to be present from the photographs I've just been sent, which is just as well as I read the S.625 valve was only in production for a very short time, although I found that apparently the ARS2 valve for an early New Zealand army radio is the same. There is no frame aerial with the set.

How does the audio side work? Is it to be heard on an earpiece or attached to a separate amplifier? Is this something that can be restored to working order? Would there be anything it could pick up today?

[Uncle Bulgaria]

Further pictures.

[ms660]

It uses a power output valve so I would think a loudspeaker, you might be able to get it working, best to reverse engineer a schematic first if there's non available.

If working it would receive MW and LW, MW was called SW back then.

Lawrence.

[ms660]

Whoops.......

https://www.service-data.com/product...68/4387/c13368

Lawrence.

[vinrads]

What a wonderful thing to be given ,I am not sure about five years to build ,but he will need a power pack building 120v dc and 2 volts dc and a grid bias battery , to start with . it will drive a high impedance speaker or fit an output transformer, and use a normal moving coil speaker three ohms. or he can just sell it to me , Mick.

[ms660]

Here's the sort of arrangement for the frame antenna(s):

https://www.radiomuseum.org/r/marcon...round_six.html

Lawrence.

[PJL]

I have a great affection for these early sets as they have a scientific instrument handbuilt look that gets lost in the 30's. The frame aerial forms part of a tuned circuit so it needs to be right but you can count the turns from the picture here https://www.mhs.ox.ac.uk/collections...entoryNo=49429.

I am not sure about using this on a regular basis as the valves will be very expensive to replace and next to impossible to find. You could construct some substitutes from later valves but the S625 is one of a kind!

[Uncle Bulgaria]

Thanks for the links. I had the same thought, Lawrence - I always forget the Service Data link, even though it's on the same screen. I've passed that on to my brother. He said he'd bring it round so I might have access soon for further photographs.

I imagine it would be good to do a restoration back to working order, if the valves are all OK. Perhaps a substitute valve selection would be good so it has some function once restored beyond being a delicate display piece.

Alternatively, if it's going to be a lot of work once I've had a look inside, and it's interesting enough to be worth something, I suppose he'd better let his friend know in case they want to reconsider the gift! It's quite a big object...

[ms660]

Note the schematic shows that the frame antenna's were center tapped.

Lawrence.

[PJL]

You have the wavelengths, 250-500m and 1000-1900m which indicates a 4x increase in wavelength so it should be possible to calculate the turns ratio between the wavebands.