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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 2nd Jan 2018, 10:37 pm   #41
Maarten
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Default Re: Vintage Television Technology.

On the other hand, valve making departments would also have been strongly encouraged to manufacture the valves that the set making department needed.
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Old 3rd Jan 2018, 11:59 pm   #42
Pieter H
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Default Re: Vintage Television Technology.

I've tried to describe this close co-operation between the Philips valve development and television set development for the first 15 years of television development here.
There clearly was a strong interaction in defining new valves based on the application requests of the set development, where the valve development application teams would make reference designs that could then be taken over quickly by set development. When this worked well, without much internal political friction, it clearly accelerated set development and performance. This was clearly the case for Philips in Eindhoven, with Valvo and Krefeld picking up quickly in the slipstream. The French organisation (including La Radiotechnique) usually followed a bit later but consistently. Mullard was a mixed basket: sometimes they were fast to implement new valves, other times they stuck to older valves much longer and/or first developed local derivatives.

Cheers, Pieter
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Old 7th Jan 2018, 11:00 pm   #43
Synchrodyne
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Default Re: Vintage Television Technology.

On triode pentodes, was the Mazda 10C2 much used, or used at all in UK TV receivers? As best I can determine, this was released in 1952, so after the ECL80 (1950) and 6U8 and 6X8 (both 1951) but before the ECF80/PCF80 (1953).

It was intended to be a VHF TV frequency changer, but whether for Band I only or Bands I and III is not so clear.

Back in 1947, Mazda had released the 6F13 high-slope pentode as its VHF TV valve in its post-WWII receiving valve range. Late in 1949, it added the 6F1/10F1, which was essentially a derivative of the 6F13, but with two cathode pinouts for higher input impedance.

The 6F13 was stated to be suitable for use in the RF, IF and video stages of TV receivers, and also as a mixer in two-valve frequency changer circuits, as shown in this advertisement from 1950:

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At that time, a pentode self-oscillating mixer was quite common for Band I-only TV receivers, so the two-valve approach would have been at a disadvantage from the valve count viewpoint. Quite why the 6F13 was not offered for use a self-oscillating mixer is not readily apparent. But for the time being accepting that it was so, one may see that to be competitive, Mazda needed to offer a single-valve mixer, and its solution was a triode pentode. Thus, the 10C2 could well have been simply a response to a Band I need, rather than anticipating a future in which triode pentode mixers were the norm.

But if the 10C2 was specified for Band III use, then Mazda was a step ahead of Philips/Mullard, whose ECF80/PCF80 did not appear until 1953. It would seem that for Band III, the pentode part needed to be specially designed for use at around 200 MHz, and I understand for example that the ECF/PCF80 pentode was somewhat different in structure when compared with the EF80. Even so, Fisher (1) said: “The PCF80 is not an extraordinarily good pentode for v.h.f, but represents the best that can reasonably placed in a miniature envelope with a high gm triode suitable for oscillator service.” Elsewhere in the book, Fisher quotes an approximate 200 MHz noise factor for the PCF80 pentode as 60. By way of comparison, the 6AK5, one of the best VHF pentodes but expensive, was quoted at 7.5, and the PCC84 cascode double triode at 5.5.


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(1) D.H. Fisher; VHF Television Tuners; Heywood, 1956. The comment about the PCF80 is on page 51. Fisher was a Pye staffer. This book provides a good picture of early British 13-channel tuner practice, in both circuitry and mechanical construction terms. Both the turret and switch types are covered.
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Old 20th Jan 2018, 12:00 pm   #44
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Default Re: Vintage Television Technology.

just a quick note reference the ECL80.
The pentode section was also used as a sound IF amplifier with the triode section, sound AF pre amp in the Philips 1114U/1427U/1100U and other models in the 'four unit' chassis arrangement including the 1400A projection receiver.
This series were noted for their exceptional sound quality.

It appears that the humble little ECL80 was capable of performing all tasks in a television receiver [at that time 1951] other than line output! John.
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Old 20th Jan 2018, 1:35 pm   #45
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Default Re: Vintage Television Technology.

Surely Frame output John, I never met one that was so good as to drive the line?
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Old 20th Jan 2018, 1:45 pm   #46
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Default Re: Vintage Television Technology.

Err. I did say other than line output valve. I'll blame the cold weather. J.
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Old 20th Jan 2018, 9:28 pm   #47
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Default Re: Vintage Television Technology.

Synchrodyne wrote: On triode pentodes, was the Mazda 10C2 much used, or used at all in UK TV receivers? As best I can determine, this was released in 1952, so after the ECL80 (1950) and 6U8 and 6X8 (both 1951) but before the ECF80/PCF80 (1953).
It was intended to be a VHF TV frequency changer, but whether for Band I only or Bands I and III is not so clear.

The Mazda 10C2 triode-pentode didn't gain much favour with TV manufactures.
It was used as the frequency changer in the RF unit fitted in the Murphy V202 series of TV receivers. It was also employed as the sync separator and timebase oscillator in some Plessey TV chassis but many of these dual heater chain sets still continued to use the ECL80 in many circuit positions.
Earlier TV receivers such as the Murphy V150U and Masteradio T917 employed the 10C1 triode-heptode as the frequency changer.
Ekco and Ultra were adherents to Mazda valves and CRT. However, looking at the circuits of those companies 1953 to 55 dual heater chain TV receivers I see that the 10C2 was not employed in any circuit position.

DFWB.
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Old 29th Jan 2018, 4:36 am   #48
Synchrodyne
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Default Re: Vintage Television Technology.

At first glance it seems odd that the 10C1 triode heptode, designed for MF and HF radio use, would be used as a TV receiver frequency changer. On the other hand, up to around 100 MHz there was a reasonable amount of flexibility in valve choices, so for Band I-only receivers, the 10C1 was not so unreasonable. Band III frequencies were more difficult, though.

In the USA, the 6BE6 pentagrid converter was specified for use in FM (88 to 108 MHz) applications as well as for AM. (Such use was covered by RCA Application Note AN-121 “Use of the 6BA6 and 6BE6 Miniature Tubes in FM Receivers.") The 6BE6 was much noisier than say the ECH81, and I’d guess that the 10C1 was more like the ECH81 than the 6BE6 in the noise department. The RCA 6BA7 was less noisy than the 6BE6, but by the time it was released, the 12AT7 had arrived and became the preferred frequency changer valve for FM (and combined FM-AM) front ends. (Although RCA itself used the 6J6 and later the 6X8.)

Anyway a heptode mixer at up to 100 MHz was, in the late 1940s, considered to be normal. The ECH81 was also specified for use up to 100 MHz. Returning to the 10C1, its triode section looks to have been similar to that of the 10C2 triode pentode, which was designed to be a TV VHF frequency changer.

Both of the Murphy circuits illustrated in the preceding post have two-stage RF amplifiers. Perhaps this was done to obtain adequate image rejection with the low IFs of the time?


Cheers,
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