Unknown make radiogram (Identified as an MRG)

[FERNSEH]

I've acquired this radiogram simply for the Garrard RC4 radio deck which will be installed in the Pye 838 TV radiogram combi.
There's no indication to the make of this quite nice radiogram. We do know that it was made in 1937, so having survived for so long it deserves to be preserved albeit with a different record deck. A Garrard RC60 will replace the RC4.
Only one valve remains in the AC mains only radio chassis, a Mullard HL13 triode, a rather odd choice of valve because this type was intended for use in 0.2amp series heater chains.
I'll remove the RC4 gram deck and store the radiogram until a there is decision on what to do with it. Don't really want to chop it up.

DFWB.

[AC/HL]

A quick flick through Radio Radio shows three radios with a similar dial, all mid 1930s.
Derwent "International five", Milnes "Diamond", and Ferguson 366.
The radio looks to me to have been a later addition.

Edit: Does this look like the chassis: http://www.service-data.com/section.php/2503/1/366

[FERNSEH]

I'll remove the radio chassis for pictures. Uses B7 valves and has a three gang tuning capacitor. It's a chassis I've never seen before.
Very rusty.

DFWB

[ms660]

The control layout looks odd.

Lawrence.

[FERNSEH]

The volume control is on the side of the cabinet.

Edit: "Does this look like the chassis:" http://www.service-data.com/section.php/2503/1/366

I've discovered the make, it's an M.R.G. Mains Radiograms Limited of Bradford.

DFWB.

[ms660]

I've never heard of them before, must be rare now.

Lawrence.

[FERNSEH]

I've never heard of them before, must be rare now.

In the 1950s MRG Limited was acquired by Radio Rentals in order that the TV rental firm could make their own sets. Later to become Baird Television. So if you think about it those post 1970 Decca TVs that were made in Bradford by the firm that first started making radiograms in the '30s

DFWB.

[ms660]

It's worth restoring if poss, quite rare, not seen one before.

Lawrence.

[AC/HL]

The Deccas weren't made in Bradford. The Decca 10, or "Bradford" as it became known, was (AFAIK) designed here, and would have replaced the 700 series, but the designer moved to Decca when Thorn took over the Baird factory.

[dazzlevision]

I agree. I have seen the Decca "Bradford" sets being made in their Pale Meadow Works, Bridgnorth factory (the former RGD, then ATM/Plessey factory).

[FERNSEH]

That's right, I forgot about the Decca Bridgnorth works. I should have remembered that as I was a pre-Tatung takeover Decca dealer. Nevertheless, the later Decca design team were same people from the MRG/Baird works in Bradford and therefore carried on the legacy of the pre-war MRG firm.
The attachment shows the above chassis view of the MRG chassis. Note the position of the HL13C valve. Possibly the local oscillator?


DFWB.

[FERNSEH]

Apart from the strange choice of audio amplifier valve which is a 13volt heater HL13C triode the receiver is quite conventional. Valve lineup is possibly: FC4, VP4B, 2D4A, HL13C?, PENA4 and a full wave rectifier. IW4-350?
Best thing to do is power it up without any valves and measure the heater voltages.

DFWB.

[FERNSEH]

Powered up the radio chassis yesterday to find out the heater voltages. The HT rectifier is a conventional 4 volt heater full wave type, so no problems there. All the other valves are 13 volt heater types so in fact the only remaining valve, the HL13C is the correct valve for this set. I'd guess the valve lineup is: FC13C frequency changer. VP13C IF amplifier. 2D13C detector and AVC. HL13C AF amplifier. PEN13C output.

DFWB.

[FERNSEH]

Link to a post started 8th December 2012 by Mark Pirate entitled Mystery Radiogram:
http://www.vintage-radio.net/forum/s...ad.php?t=91227

It can be confirmed that Mark's radiogram is also an MRG.

The output valve was a Mullard PEN13C a valve which is almost impossible to find.
The Brimar 7D5 can be considered a suitable replacement. The electrical characteristics are similar to the 6F6.
http://www.radiomuseum.org/tubes/tube_7d5.html

DFWB.

[FERNSEH]

This radiogram is now just over eighty years old so it wouldn't be very sporting to destroy it considering that it has survived so long.

The original lacquer has been removed from the cabinet surfaces and French polish applied. The front and sides have very nice veneer patterns. The cabinet lid is a bit bland looking but will still polish up nicely.
The Garrard RC120H is the three speed record deck chosen as the replacement for the original RC4.
In 1945 the MRG firm was acquired by Radio Rentals.

DFWB.

[FERNSEH]

Meanwhile, the MRG is receiving attention. Even in it’s pre-polishing condition it does look quite smart. Coming up next. I must find a 10″ diameter loudspeaker. As I can’t find a decent energised one, a PM ‘speaker will be used instead and so it will be necessary fit a separate smoothing choke. The smoothing choke will be fitted on the radio chassis rather than on the loudspeaker frame. The output transformer was designed to match the characteristics of the Mullard PEN13C, but because a Brimar 7D5 is the replacement for the hard to find Mullard valve, it’s likely that a different output transformer will be required. The 7D5 characteristics are similar to the 6F6G or KT63. The RS components transformer 210-6475 could be considered.

DFWB.

[Nuvistor]

That TX should be fine, it will match the 7k anode load to 3,8 or 15 ohm speakers. It has a max current of 40ma and the 7D5 is max anode current of 38ma, I don’t think you will be running the valve at max anode current.

[FERNSEH]

Hi Frank,
from the Radiomuseum, info about the 6F6G:
https://www.radiomuseum.org/tubes/tube_6f6g.html
The Mullard PEN13C:
https://www.radiomuseum.org/tubes/tube_pen13c.html
The Radiomuseum suggests that the Brimar 7D8 is an equivalent of the PEN13C, Ra 6.4Kohms @ Va = 250V. However the Brimar valve book informs us that the characteristics of the 7D8 are similar to the 6AG6G, optimum load 8,500ohms @ Va = 250V.

DFWB.

[FERNSEH]

A 10" PM loudspeaker will replace the missing energised unit. The field coil has been replaced by a conventional smoothing choke. Because there is no space on the chassis it's mounted above the mains transformer, see first attachment.
The 8 + 8 microfarad smoothing capacitor is dated June 50. It was carefully reformed over a long period of time but in use the hum level was rather high, it really needed replacing. Well now it will need replacing, see the second attachment.

DFWB.

[Heatercathodeshort]

Well you could try stuffing all those bits back into the can, a true restuff!

Oh dear, I should not mock [but I will].. That is a rare occurrence David. I only had that happen a handful of times in over 50 years.

It will soon clean up and knowing those rugged old rectifier valves, the IW4 350, I would say it has survived. I hope you had a convenience that was quickly accessible. Regards, John.