HMV 520 Radiogram - general interest.

[Bouc Bel Air]

We have just aquired an HMV 520 Radiogram. We live in France and think this unit was built in the U.K and exported to France. The unit needs a bit of restoration work but my wife is an interior designer and furniture restorer and I am an electrical engineer so we should have no problem restoring it. Electrically it is quite sound although it requires some minor restoration work on the cables so we have yet to apply any power. Any information anybody has on this radiogram would be gladly accepted by ourselves. We would also be interested in any other websites which could point us in the right direction for spare parts etc.
Thanks in advance
Helen & Adrian Dawes

[Bouc Bel Air]

A Picture

[paulsherwin]

Hello Helen and Adrian.

You were right not to apply power. This is a *very* old piece of equipment and would be specialist work even for experienced radio restorers. If unrestored it will almost certainly need some components replaced before use.

Work on old radios (especially this old) involves a different skillset to that of a modern electrical or electronic engineer so you would be wise to tread carefully, especially given the rarity of this item. In particular, never forget that valve equipment uses high voltages which can kill, and electrical safety standards were very different then.

You can find general advice on valve radio restoration elsewhere on this site, including precautions to take when applying power for the first time:

http://www.vintage-radio.com/repair-...on/index.shtml

This forum is also a very useful source of help and advice on specific issues.

HTH, Paul

[Bouc Bel Air]

Hi Paul
Thanks for your sound advice and very quick response.
I agree with you about the valve skillset but I am very lucky in having a good friend who will have no problem in handling that part of the project for me. I am used to working on and rebuilding old D.C. control and switchgear which is still in use in the shipping industry although is getting rarer so I have some understanding on how carefull I should tread.
We hope someone will point us in the right direction for finding out more information on the radiogram, age, circuit diagrams, handbook or a similar unit we could possibly utilise information from. I have attached a picture of the internals of the unit and will post a picture of the turntable later in the hope someone will recognise it.
Many thanks again
Helen & Adrian

[Bouc Bel Air]

Turntable Picture

[paulsherwin]

Adrian, it's very possible *nobody* will recognize it. These luxury early 30s models were made in relatively small quantities and very few survive. I couldn't find any service info on Paul Stenning's CDs. You may need to use general principles to restore it, looking at standard circuits used in British radios at the time.

It does look nice and complete though. These radios often have their output valves removed, as they are highly prized by Taiwanese audio enthusiasts for some reason.

Good luck, Paul

[Paul_RK]

It is a very early and a very rare, quite possibly unique, radiogram. The date will be between 1928, when HMV's production of electrically amplified instruments began, and 1930: that much is evident from its style alone, but everything from 1931 on is much better documented, and I've not been able to unearth any reference to this model. Even in 1930 HMV's business was overwhelmingly in acoustic gramophones, and according to the book "The Setmakers" (Geddes and Bussey) their entire production in that year of electrical reproducers of all kinds amounted to some 5000 units.

Service information for equipment from before 1930 is, with a few exceptions, notoriously difficult to find. The circuitry itself, though, is unlikely to be very challenging. Most of the difficult decisions when it comes to restoring something like this concern how much to change, sourcing of the most appropriate replacement parts (including wiring etc., as most of us feel for instance that bright PVC-covered wire in such a machine is somewhat of an abomination), and in general how much effort to expend on maintaining something of the internal as well as the outward appearance of the radiogram. Generally it comes down to a labour of love on someone's part: the monetary value even of a fully restored radiogram that has a fair chance of being the only one of its kind remaining would generally fall short of justifying any significant number of man-hours put into the restoration. To the discomfort of many of us here, as Paul has suggested, it may not be much more than the going rate for the triode output valve.

I can't think of much more to say except to wish you well with the task ahead. Making a schematic drawing of the circuitry would be a good and helpful early step toward restoration, probably not too difficult for a set like this if you're able to recognise the various parts. Service instructions should be relatively readily available for the induction disc type (at least I think that's what it is) gramophone motor.

Paul

[yestertech]

Helen/Adrian - You're in luck ! I have consulted my HMV folder and found a tiny original pamphlet entitled
"service manual #1 Model 520 Radio Gramophone"
It is dated March 1930. and contains some great illustrations on erecting a suitable aerial for this beast !
The valve line up appears to be U9 RECTIFIER , PX4 OUTPUT, MH4 LF ,MHL4 DET ,& MS4 HF . Probably all still fine, but pray that the PX4 is OK as these will now be difficult to source !
There is also something called a "POT RECTIFIER" which supplies 160 V DC to the speaker electromagnet and 4 volts for a pilot lamp - This is another U9. This is the small chassis sitting in the base of your photo

The leaflet contains a wiring diagram for the various sub assemblies, the circuit of the radio/amplifier unit ( where the rectifier appears to have become U10 ) and some fault finding charts. There is also a component layout for the radio/amp unit.

As was mentioned above, the gram is an induction disc motor.

I am happy to photocopy/enlarge this info. for you and post out for a small contribution.

Regards

Andy

[Bouc Bel Air]

Guys
Thank you for all the information, to be honest we were getting a little downhearted as we want to start the project but wont until we have enough information at hand. The cabinet is no problem for my wife and I intend to keep as much of the original cables as possible, I too do not like the idea of highly coloured cables in something like this, damaged cables I can remove, cover in black heat shrink and replace or, bind them if I can get the cotton. Anyway our plan is to have a fully restored working machine as original as possible.
Andy we would be most greatful if you would send us a photocopy,please let us know your costs, address etc and we will send you a cheque.
Just to let you know we were not interested in the value of the gram but thanks anyway, to be honest we didnt think it would be worth all that much as we only paid the equivalent of 50 pounds anyway so we were pleasently surprised.
Anyway thanks again for all your help so far and if anybody else has any more info please let us know.
Best Regards
Helen & Adrian Dawes