Peter's Nostalgia Site
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The Complete Range of EMI First Generation Television Sets
For the 1936 Radiolympia, EMI presented four television models, the two television only sets, the 702 and 901 along with two outwardly very different sets that included a four waveband radio offering Medium and Long wavebands and two Short wavebands covering from 16.7 metres to 141 metres. These were the HMV 900 and the Marconiphone 701. Both sets were priced at 120 guineas as against 95 guineas for the television only models. The radio chassis was similar to that used in the Marconiphone 345/6 or HMV 480/1 but with a different tuning scale. The 345 is reviewed here and had a list price of 17½ guineas. Apart from slight differences regarding the CRT sizes the circuitry of the two television/radio models was identical to each other and also to that of the vision circuits of the 702 and 901 although mechanical chassis design of the timebase and power supply differed. The sound signal in the television only sets was passed through a superhet receiver with an IF of 1.5 MHz whereas in the television/radio models the television sound signal shared the same 460kHz IF used for the radio broadcast signals.
The HMV 900 looked similar to a conventional radiogram of the period with an opening lid to access the controls and fitted with a mirror for viewing the television picture displayed on a 12" CRT.
In contrast the Marconiphone 701 had two lifting lids to give access to the television controls on the left and radio controls on the right of a raised section where the picture was viewed from a 9" CRT via a fixed mirror and magnifying lens. A possible reason for using the 9" CRT was to reduce the overall cabinet height. (The 12" Emiscope 6/6 is 28" long and the 9" Emiscope 6/5 is 23.5" long.)
By March 1937 the 120 guinea sets had dropped in price to 80 guineas and the 95 guinea sets to 60 guineas and the frontal appearance of the 901 had been revised but the lower prices no longer included the cost of aerial installation.
Two months later in May 1937 the model range was extended to include models incorporating television, radio and gramophone. Service information for the gramophone can be found here. The sets were the Marconiphone Mastergram 703 and the HMV 902, both priced at 120 guineas with aerial included. The television picture of the 703 was displayed on the mirror lid reflected from the same 12" CRT used in the 702, 900 and 901 models. Circuitry was again very similar to the earlier models but the CRT cage and the timebase and power supply chassis were mechanically more like those in the 702 and 901 rather than the 701 and 900 models.
The 902 used the same 9" CRT viewed via a mirror and magifying lens that was used in the Marconiphone 701. However, a later version, designated 902A used a 12" CRT without the lens and mirror. This was not the Emiscope 6/6 used in the other 12" first generation sets but an Emiscope 6/7 that was only 23" long thus permitting the CRT to be horizontal and direct viewing. Jürgen Valter gives us a very good description of his 902 thanks to the medium of 405 Alive and the BVWS.
Looking at the photo below taken in February 1939 it's possible that EMI may also have prototyped a version of the 701 using the direct view 6/7 CRT as fitted to the 902A and the control room monitors. Just for comparison the screen shot on the right was photographed 83 years later from the screen of a mirror view 6/6. Note the general darkening of ion burn in the central circle . The switch off spot is quite similar although it appears on top of the cube rather than above it on account of the different scan centring.
The HMV 903 and Marconiphone 704 first appear in an EMI Technical Circular for Sales and Service in April 1937 and at that time were fitted with the 9" Emiscope 6/1 CRT that had a green phosphor but even more strangely they were not shown at Radiolympia until 1938. The 903 and 704 schematics differ considerably from the other first generation sets and their CRTs are direct view rather than viewed via a mirror. It is thought that a 9" mirror lid set, that came to light some years ago, may have been the prototype for the circuitry used in the 903 and 704. Their receiver circuitry differs from the straight TRF vision circuits used in their stable mates in that they have superhet circuits with a sensitivity of 500µV. This is rather less than the 200µV claimed for the TRF sets with full bandwidth but is possibly looking forward to the roll-out of transmitters in other regions. Both sets had 45 guinea price tags in 1938 but did not include the aerial/installation. Ken Brooks reviews Marconiphone 704 serial number H/1 13096 here. From the slight damage to the right hand edge, Ken's 704 would appear to be the same set that is shown in the video Marconiphone 704.
If we ignore the Marconiphone 708 projection receiver that was really a non-starter then the last of those using the first generation circuitry was the Marconiphone 705 that appeared in the 1938 catalogue. This set was essentially the same as the HMV 900 but with a slightly different cabinet. It was priced without aerial installation at 80 guineas. On the assumption that the Marconiphone 701 had a higher manufacturing cost than the HMV 900 a possible reason for this model may have been to provide a set with the same capability as the 701 but appealing to Marconiphone customers whilst using up obsolete assemblies with a greater profit margin.
* Note that in this photo whilst the general layout is correct some non-original parts have been fitted.
EMI Next Generation Pre-War Television Sets
The Wireless World Olympia Report covers the EMI sets in August 1938.
The HMV 904, 905 and Marconiphone 706, 707 only differed in cabinet styling and each was offered with a choice of 5" or 7" CRT.
Sets with 5" CRTs were priced at 29 guineas and 7" sets at 35 guineas. The Wireless World gives us a 3 page feature on the HMV models in September 1938. Hugo Holden gives a comprehensive account of the restoration of an HMV904 here. Andy Beer overcomes a daunting restoration of an HMV905 that was missing a large part of its circuitry here. Andy was not alone in his enthusiasm for these sets. Victor Barker was successful in building an even more ambitious recreation of an HMV 904.
Also introduced for 1938 were the HMV 907 and Marconiphone 709
Once again the only difference between the two sets was the cabinet styling. The CRT was 9" diameter. Both sets carried a 45 guinea price tag. Steve Osler takes us through a very comprehensive restoration of an HMV907 here.
The Television & Short-Wave World Olympia Report of September 1939 covers the EMI sets.
Had the war not intervened then the 1939 generation of HMV sets would have been the 1800 range. The 1800 was a table model with a 10" CRT. The 1801 was a very similar set in a console cabinet and the 1802 again similar but with a 14" CRT. The 1850 added a push-button radio to the 1802 spec, similar to the HMV1103. Thanks to the researches of Norman Green we are fortunate to have a copy of a report on this range written by Alan Blumlein for the attention of Isaac Shoenberg on the 23rd August 1939. David Boynes commented that the difficulties in achieving good video bandwidth were probably a consequence of the relatively low 8 MHz vision IF when compared with the HMV901 where it was much easier to attain 3 MHz bandwidth from its 45 MHz TRF receiver. Perhaps not so important for the smaller screen models but more noticeable on the 14" screens. The 901 alignment instructions offer four stagger settings trading bandwidth for receiver gain. The widest offers 200µV sensitivity. The "Normal" stagger gives 50µV, "Narrow" 20µV and the "Extra Narrow" 10µV. The typical IF response for the 1800 series sets is plotted below and it looks much better than the 1.2 MHz quoted in Blumlein's report.
At this time motor vehicle ignition interference was clearly a major issue and this continued to be a problem after the war.
The exhibition generated a lot of public interest. Around 2000 people each day were able to see a wide range of television receivers demonstrated showing the Alexandra Palace transmissions during broadcasting hours and at other times a Cossor flying spot transmitter provided films for display on the receivers. See Wireless World: here & here.
Quoting from Television & Short-Wave World July 1937:
"If television is to become popular it is essential that the general public should be made aware of the vast strides that have been made and that they should realise that here is a new form of entertainment within the reach of many. Despite the publicity that television has received during the past few months it is quite evident that there is still a large section of the public who are not aware of its possibilities and limitations, and we suggest, therefore, that our readers would be doing television a real ser-vice by inducing their friends to visit the exhibition at the Science Museum so that they can see for themselves what an advanced stage has been reached.
The exhibition is free and it is open at convenient times. We have heard the criticism that there is much at this exhibition that the average person cannot understand, and that the many details are bewildering, a criticism which is doubtless true, but a fact which does not in any way detract from the value of the exhibition except that it may lead some people to think that television is such a complicated matter that the proper operation of a receiver requires expert knowledge. That this is not the case needs no stressing so far as our readers are concerned, but this impression undoubtedly exists in the public mind, and we make the further suggestion that our readers should do what they can to dispel the idea.
Of the ultimate future of television there can be no doubt. At the opening ceremony of the exhibition, Lord Selsdon said, "British television was ahead of the rest of the world. England was the only country where the public could receive a regular programme in their own homes." And Sir Noel Asbridge, Chief Engineer of the B.B.C., gave it as his opinion that the establishment of a service which would cover the whole of the populated areas of this country was not an improbability. How soon this latter will be an accomplished fact depends largely upon public interest.
No one who saw the Radiolympia demonstrations last year can fail to
appreciate that since then very great progress has been made, and it is
significant that we have not heard any adverse criticism regarding the quality
of picture that is now being obtained. Also it is gratifying to know that the
veil of secrecy that has hitherto been over television has at last been removed;
the sooner the public knows all about it, the sooner will it be disposed to buy
receivers. The organisers of the Exhibition are to be congratulated upon getting
together a most representative show, and for the first time giving the public an
opportunity of seeing television as it really is to-day."
As well as the displays of CRT televisions Mihaly-Traub had a display of 405 line mirror drum equipment and Scophony demonstrated a domestic sized receiver with screen 24" x 22" and a large screen model 5' x 4'. At this time the line and frame timing of the Alexandra Palace transmissions was referenced to electronic sources that didn't guarantee the short term stability required by Scophony with the inertia of their mechanical systems and so they provided their own signal source that was 240 line 25 Hz non-interlaced. 405 line interlaced operation became possible for Scophony once the BBC derived their reference signals from a mechanical pulse generator.
Also on display was a beautifully detailed scale model of the Marconi-EMI Outside Broadcast van with a removable roof.
..and the real Marconi EMI Mobile Television Unit.
Some outside broadcasts were more daring than others.