Classic cars forum & vehicle restoration.

[peter scott]

When I was a kid I used to love visiting The Royal Scottish Museum here in Edinburgh. It was a fascinating place crammed with wonderful technological exhibits and the one that fascinated me the most was a 1936 HMV television.
This was displayed so that you could see all the works and it used really vintage technology, valve types that dated from the early 30s. The tube had a very small deflection angle and was therefor rather long and had to be mounted vertically in the cabinet and viewed through a mirror in the lid.

Anyway, time moved on and the Science Gallery shut down for (many years)
of renovation. Unfortunately by this stage the display designers had got their paws on the place and my favourite exhibit had been consigned to the store room.

Here are a couple of shots of the museum's set in store.



Moving on further in time I subscribed to a newsletter for old radio nutters and decided to place an advert for a television like that in the museum. There weren't that many built and of course the survival rate was very low but much to my surprise I got a positive reply. The only slight drawback was that I was in Edinburgh and the set was in Cornwall. As I recall the guy wanted £100 for it. This was 30 years ago and that was quite a lot of money but we set off in our Reliant Rebel Estate (which had cost less than the tele.) and needless to say I bought it. Being a fragile box of tricks it lay on a double air mattress in the back and did survive the journey.

Having not been used for many years it took me quite a bit of time to get it working. The worst problem was the mains derived EHT transformer that was burnt out but fortunately my employer had a transformer shop at the time and after a couple of goes at rebuilding it I got a design that gave sufficient insulation to work and survive.

The set was only designed to receive signals from Alexandra Palace (Channel 1) so I needed to build a little converter to get it working from our local Channel 3 transmitter. That worked fine until the switch off of the
405 line service in the late 80s after which my set lay fairly dormant until a
few years ago when I build a 625 to 405 line standards converter based on a very clever design by a German enthusiast.

You can see some shots of my set here:
http://www.nostalgiatech.co.uk/Vintagetech.htm

[Rick]

Very interesting that Peter, I like the lengthy instructions for firing up the TV

R
_________________
Rick - Admin
Home:https://www.oldclassiccar.co.uk
Videos:https://www.youtube.com/user/oldclassiccarRJ/videos
OCC & classic car merchandise (Austin, Ford ++):
https://www.redbubble.com/people/OldClassicCar/shop

[47p2]

I enjoyed that Peter, you have a very interesting site
_________________
ROVER
One of Britain's Fine Cars

[Greeney in France]

As a radio nut peter perhaps you understand this little beauty
It has some good interesting history too It stands a good ft tall+

_________________
www.OldFrenchCars.com

We do these things not to escape life but to prevent life escaping us

[peter scott]

Thanks for your replies guys.

I've never been involved with transmitting equipment Greeney but I think
that bottle might be a 4212E designed as a powerful audio triode for modulating medium powered broadcast transmitters. A push-pull pair can give something like 1kW of audio power!

Peter

[Greeney in France]

Geniusssss
I was told it was used at Alexander palace powering the first transatlantic telecommunications. These were dismantled and destroyed later but 2 seemed to "get out" I have one and a friend has another, It is on display now and whenever anyone sees it, it always creates a discussion, it is supposed to glow blue when connected
_________________
www.OldFrenchCars.com

We do these things not to escape life but to prevent life escaping us

[peter scott]

Hi Greeney,

I do have some information on the vision transmitter that fed that famous Alexandra Palace transmitting aerial before the war but I don't have anything on the sound side.

It is quite usual for VHF transmissions to travel trans-atlantic distances but I think the occasion you are refering to was captured on film and strangely constitutes about the only cine record of Pre-War British television in existence. http://www.apts.org.uk/recording.htm

Your valve is a lovely exhibit and as you say will have had a nice blue glow whilst in operation. Today's semiconductor equivalents are cold fish by comparison. A bit like comparing steam locos to modern day electrics.

Thanks for posting the pic.

Peter

[Greeney in France]

Thank you Peter I have never had more than a minute understanding of it but would it have had anything to do with early "telephone" or was it purely audio transmission
I do love the thing it is so intricate inside
_________________
www.OldFrenchCars.com

We do these things not to escape life but to prevent life escaping us

[peter scott]

Hi Greeney,

My understanding is that your valve was designed in the 1930s and its principal application was as an audio amplifier within a wireless transmitter. Prior to microwave links and satellite communication I think almost all long distance telephone traffic travelled over cable systems. Undersea cables generally relied on a series of repeaters (amplifiers) spaced along the cable but these used much lower power technologies. http://www.platinummetalsreview.com/pdf/pmr-v2-i1-002-006.pdf

You mentioned an Alexandra Palace connection. The south east corner of Ally Pally was converted into television studios and transmitter in about 1936 but this transmitter was solely for television and the building had no other previous use in broadcasting or telecoms.

Initially, in 1936, during the trial period when the Baird 240 line system was transmitting week about with the Marconi-EMI 405 line system, there were three transmitters. The two companies shared a sound transmitter broadcasting on 41.5MHz but each had their own vision transmitter on 45MHz. Your valve doesn't have the correct characteristics for use in the vision transmitters but it could very well have been in the modulation amplifier of the sound transmitter. I do have details of the Marconi-EMI vision transmitter but, unfortunately I can't find any detailed info on the sound transmitter.

Apart from television use both sound and vision transmitters also served during the war to confuse the German bomber navigation systems.

After the war, the television service from Ally Pally was recommenced but the transmitter was closed down in March 1956 when the new Crystal Palace transmitter opened. I think the Ally Pally mast still does some analogue television relay work and it also transmits DAB digital radio.

I don't know when the sound transmitting equipment was removed from Ally Pally. Do you know when your valve left the building?


Peter

[peter scott]

Here's a picture of the sound transmitter from Ally Pally.. yes all of it.

The pipe coming out of the top of the centre cabinet is the feed to the aerial.



I'm not certain but I think the two big bottles in this audio amp from the European Triode Festival could be cousins to your 4212E.
http://www.timebanditaudio.com/ETF2006/etf2006.html

[Roverron]

Very interesting, I was at the model engineer exhibition at Alexandra Palace a few years ago and there was an illustrated lecture about the building and early years at Alexndra Palace which was more interesting than the models
I was an apprentice to a man who remembered working on a gas radio, don't think there was a gas television but it would be a possibility
_________________
To Hell with ambition, it drives a man mad, I can scarcely wake up to be fed.

[Greeney in France]

Peter that is really interesting stuff and ties in with what I was told
I have had the thing for 20yrs. It was given to me by an engineer whom worked for my maintenance company. I employed him until he was 65 and when he left he "presented me" with the valve because I had always liked it. He said in all his year employed he had never worked for a better boss

He told me his dad had worked at Alley Pally after the war and told me it was a part of the first "telecommunications across the Atlantic"when they dismantled the equipment in the early 60s they were told to physically destroy everything but he managed to fritter away 2 valves.
I do look after it and the guy is still alive
_________________
www.OldFrenchCars.com

We do these things not to escape life but to prevent life escaping us

[pigtin]

My first brush with electronics was trying building a radio control set for a model aircraft in the early fifties.
The reciever had just one valve, a gas-filled triode XFG1 I believe. I cycled all the way to Kingston to buy a escapement from E.D. manufacturers of model aircraft engines an radio control sets.
The transmitter also had only one valve a DCC90, very expensive, but I was an apprentice at Phillips/Mullard at the time and managed to get one cheap.
Never really had the set, and an aircraft working at the same time but it was great fun.

[peter scott]

Hi Greeney,

I'm glad the history is fitting together. A real shame that the equipment was distroyed.

Hi Roverron & Pigtin,

Looking at the picture of the amplifier above am I right in thinking that the XFG1 would nicely continue the size ratio started by the adjacent valves in the photo?
I never got into radio controlled models although I still have a scar on my index finger from a Frog 5 cc monster that objected to me trying to start it.
Having said that, in more modern times one of my ex-work colleagues did some kite aerial photography that almost kindled my interest in such things.

Take a look at this lot..

http://www.gentles.info/KAP/Index_KAP.html


Peter

I've not asked James if I can show one of his images here but I'm sure he won't mind..

[pigtin]

Peter, I'm a bit late finding last posting... regarding the XFG1. It was seen as 'ultra minature' in its day (early 50s) being just over an inch long and having wire ends. I seem to recall it costing a little less that 25 shillings. But the downside was: it would only last about 20 hours before the gas colour started to change and it was declared 'Soft'.
Mind you; any one who could get a model airplane to last 20 hours without losing, or terminally crashing it, was considered very fortunate.

Don.