|
Peter's
Nostalgia Site Interests
|
|
|
Early Days In 1934 the Marconi-EMI Television Company Ltd was formed bringing together the vision transmitter technologies of the Marconi Company with the television studio equipment and receiver technologies of the EMI Company. It was this company that provided the technology for Britain's television service in the years from 1936 through to the switch-off of the 405 line transmissions in the early 1980s. The very first dedicated television receivers developed by this alliance were the HMV model 901 and the Marconi model 702. These sets were essentially identical but had differences in the veneering of the cabinet and the shape of the speaker grill so as to appeal to traditional customer loyalties for the two brands. The same design of television circuitry was also incorporated into a number of other sets carrying the HMV and Marconi names that included radios and gramophones. This web page takes a look at one of these early receivers. The HMV 901 Television
In January
1935 the Selsdon Commitee, whose brief was to advise on the future of
television, made its report. It proposed that the BBC set up a
television station in London but it was unable to decide on whether the
240
line Baird system or the 405
line EMI system
should be used and thus both systems should be trialled. The HMV 901
was one of the sets designed to meet the needs of this trial period.
The early production units were fitted with a "System Selector Switch"
and one additional valve in the timebase chassis. Blanking plates were
fitted to the switch panel of sets manufactured after the decision was
taken to proceed solely with the EMI system and most early sets also
had their switches removed if they were subsequently refurbed by the
factory.
The System Selector Switch has 4 poles and is marked S1 in the old timebase schematic. See Service Info.
The Trial Whilst EMI took a very large gamble in deciding to develop a 405 line system based on the Zworykin Iconoscope there was really no contest when it came to the trial. The Iconoscope camera gave sufficient sensitivity to permit both studio and outside broadcasts due to its charge storage technique and cameras were portable although restricted by connecting cables. Against this Baird really had no practical camera. For studio work he was forced to employ either a spotlight scanner where the subject was scanned by a single point source of light in a darkened room whilst groups of photo cells picked up the reflection or a cine film camera that was fixed to a massive high speed development bath combined with a mechanical scanning disc. The latter had to be bolted to the floor and mounted behind a glass window to suppress its noise. The only electronic and therefor portable camera that Baird had was the Farnsworth Image Dissector which, unlike the Iconoscope, had no charge storage and relied on an electron multiplier to achieve any form of sensitivity. The Farnsworth camera proved to be virtually unusable due to its lack of sensitivity and thus almost all Baird's transmissions were derived from mechanical scanning. For a fuller account of the start of High Definition Television in Britain see: BFI ScreenOnline
Production Changes The Wireless World tested a very early model of the HMV901. In
the
photos below you can see the following differences with later models:
Whilst there don't appear to be any survivors of the early WW style HMV901 the earliest surviving sets do have the longer CRT metalwork and the components of the additional valve used to maintain regular line timebase behaviour through Baird System frame synch pulses. The set pictured below has the longer CRT metalwork and a vacant valve holder on the left of the timebase chassis whereas other sets have blanking plates. I believe that sets without the Baird circuitry have their plates mounted on the underside of the chassis whereas sets that do have the circuitry fall into two camps, those with and without a plate. In this case the plate is mounted on the top side of the chassis. These plates could have been fitted at a subsequent refurb but this would have required the valve holder rivets to be drilled out so perhaps these plated sets were just the last production run prior to Baird deletion.
A Prototype HMV901 / Marconi 702 ?
A few years ago a set came to light that externally looked rather similar to the HMV901 that Wireless World tested. This may very well have been a prototype for the HMV901 and its cousin the Marconi 702. The set differed from the WW set in that it had its controls mounted on the front of the cabinet and a 9" CRT instead of the 12" but it had a very similar veneering pattern and design of speaker aperture. The owner believed that it had been displayed at Radiolympia in 1937 but this seems at odds with the reports in Wireless World. There are quite a number of reports and of course a substantial interest in television at the time and whilst the models on display were clearly referred to there is no mention of this set in either the 1937 or 1936 Radiolympia reports. If it was a prototype for the 901/702 and the other sets that shared this generation of design, then it would be at least a year older than the 1937 date quoted by the owner. It certainly bears little resemblance to the second generation of EMI televisions so it seems unlikely that it was a prototype for anything later than the first generation. The chassis was totally different to the HMV901 / Marconi 702 and mounted at a slight angle to the horizontal and divided into a timebase on one side of the CRT and an RF amplifier on the other. It appeared to have one fewer RF stages than the 901/702. The power supply was mounted in the floor of the cabinet and the EHT parts were shielded in similar style to the 901/702. The set had no back panel and no obvious way that one was ever fitted. Nor did it carry any HMV or Marconi decal or serial plate but given its appearance and construction it seems very likely that it is a prototype for the very first commercial EMI television receivers.
Studio Monitors Given that Marconi-EMI were supplying all the studio and transmitter equipment then it's no surprise that the BBC also used their domestic receivers as studio monitors. The viewing window on the right of the control room sketch overlooked the EMI studio and can also be seen in the centre of the Alexandra Palace cut-away drawing.
When I
was a kid I used to love visiting The Royal
Scottish Museum 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. The model 901 was displayed so that you
could see all the works and it used really vintage technology, valve
types that dated from the early 30s. For me,
growing up in the 1950s, television was a modern thing but here was a
television from the past. 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.
Moving on further in time I subscribed to a newsletter for old radio enthusiasts and decided to place an advert for a pre-war television. At the start of the war about 16,000 sets had been sold in Britain but I was aware that the survival rate was very low. Whilst some early televisions had formed parts of radios and radiograms I really wanted one that had no other purpose than as a television and ideally it should be manufactured by EMI given that it was their research and technology that had led to the birth of real television in Britain. My ideal was either a Marconi 702 or an HMV 901. I received two replies to my advert, one from someone else looking for a pre-war set and asking if I could pass on any replies that I wasn't interested in, and much to my delight, a reply offering an HMV 901. The only slight drawback was that I was in Edinburgh and the set was in Cornwall. As I recall the seller 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 HMV) and needless to say I bought it. Being a fragile box of tricks it lay on a double air mattress in the back of the car and did survive the journey. Below: Following purchase in January 1979 the HMV901 is loaded into the back of my Reliant Rebel for the 500 mile trip back from Cornwall to Edinburgh.
![]() The 405 line broadcasts were closed down in 1984. In the years leading up to 1985 the broadcast authorities produced programs using the current 625 line standard and with the aid of a 6 foot high rack of equipment were able to generate 405 line versions of the same programs to maintain the old service. Technology has moved on considerably since 1984 and a number of innovative designs have been produced for standards converters in recent years. Instead of 6 feet of equipment, the converter can now be contained in a small metal box.
Darius and his first converter.
You can get more detailed information about Darius' standards converter here
Clips from an early television demonstration film This is a short video of the HMV901 displaying clips from a 1937 television demonstration film. The video and sound signals are being converted for 405 line operation and modulate the original 45MHz/41.5MHz carriers which are fed into the aerial socket of the HMV901. Occasionally you will see narrow dark horizontal bands on the the picture. These are only aliasing effects from the camcorder that is capturing the scene and are not present in reality. It is probably best to click on the full screen button in the bottom right corner. (Esc takes you back to normal view.) ..and a shorter video of the fashion parade
Viewer Reactions In October 1936 the Wireless World reported the impressions of an observer in Welwyn who had been watching the early program material from Radiolympia and Alexandra Palace. "The features which drew the greatest appreciation were the outdoor shots at the Alexandra Palace grounds (which never failed to excite the astonishment and wonder of those who had come with no idea of what modern television can do), the variety entertainment in the studio, with its striking use of successive shots from various angles, and, among the films, the news reels and the excert from "Show Boat." On the other hand, in studio programmes, head-and-shoulder views and interviews soon bored the watchers. Frequent change of scene and viewpoint seems to be probably even more important in television than in the cinema. This is where the variety show scored, and although the "Show Boat" excert was simply of Paul Robeson singing "Ol' Man River" the film producer has presented this song with rugged simplicity of masses, and of light and shade, that it makes perfect television entertainment. Films with intricate small detail (particularly noticeable in captions) and films which were static, were the least effective. >The lighting of studio scenes seemed to vary considerably, but of course in this, and in the matter of make-up, the television producers will have to feel their way for some time. When the camera moved rapidly towards or away from an artist there was a frequent tendency to go out of focus, evidently because the cameraman has at present no sufficiently positive rapid-focusing device. The most remarkable effect of television in my house was its enthusiastic adoption by children. They have never shown any great interest in sound broadcasting - even the Children's Hour. But television they watched with rapt attention, and with screams of laughter for the comic horse in the variety show; and not merely once. They insisted on seeing the programme through again and again as it was repeated daily for Radiolympia. They never tired of it, which seems to indicate that it was not the "novelty appeal" of television which was having effect, but real entertainment value." After the official opening ceremony on 2nd November 1936 the following programs were listed...
....and when there was nothing else, you could always sit and watch the test card.
Oldest Working Television Jeffrey Borinsky holds the title for the oldest working television in Britain. Jeffrey's set carries the Marconiphone badge and has a slightly different cabinet design but is otherwise the same as the HMV901.
|