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Old 22nd Jul 2018, 11:10 am   #41
FERNSEH
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Default Re: Philips 819 line TV receiver.

Circuit diagram of the sync and timebase oscillators with most of the component values identified.
The line sync pulses are filtered out by the 220K resistor and 2200pF capacitor and the frame sync pulse is supplied to the triode section of the PCF80 sync separator valve.
The line oscillator valve is a PCF80 and operates in the cathode coupled mode.
The resultant waveform at the anode of the pentode section has a peak amplitude of 200volts.

DFWB.
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Old 22nd Jul 2018, 12:59 pm   #42
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Default Re: Philips 819 line TV receiver.

Quote:
Originally Posted by peter_scott View Post
The German 441 line stuff doesn't appear until late 1937. There was some dabbling with 375 line after Telefunken bought the rights to RCA iconoscope technology but I think it's true to say that all the 1936 Olympic television was 180 line as the public viewing rooms were not equipped for any higher standard.

Peter
Hi Peter,
was the 180 line sync pulse train generated by mechanical means or electronic pulse generators?
Line count apart it's likely the video waveform resembled the Baird 240/25 system and will have only one broad frame pulse.

Did read somewhere that in France a 320 line mechanical TV system was realised.

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Old 22nd Jul 2018, 3:35 pm   #43
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Default Re: Philips 819 line TV receiver.

Hi David,

Yes, it looks as if the German 180 line system has just one broad pulse. This WiKi talks about 375 lines in use with the Telefunken Fernsehkanone but I think that in general they must have been running them with 180 line for compatibity with the viewer room sets.

https://en.wikipedia.org/wiki/180-li...evision_system

I don't know what they did for a synch reference. The intermediate film stuff must surely have been mechanically referenced but I've not found very much on the Farnsworth or Iconoscope references.

Peter
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Old 22nd Jul 2018, 3:51 pm   #44
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Default Re: Philips 819 line TV receiver.

Hi Peter,
According to Wiki the frame sync pulse was 200microseconds wide.

Interesting to not that the video to sync ratio was 75:25. Wasn't the Baird 50:50? Evidently the deep syncs were necessary because the black level clamping wasn't so good as M-EMI.

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Old 22nd Jul 2018, 4:26 pm   #45
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Default Re: Philips 819 line TV receiver.

May I add an info? The Barthelemy method for synchronizing during the mechanical TV era, was to add a single pulse in the black portion in every single frame. In this, He was using a different method from Baird who send a sync pulse for each begining line. As far as I know, Barthelemy used the same sync method with the 180 lines cam.
Sorry for being out of subject.
Roger

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Old 22nd Jul 2018, 4:57 pm   #46
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Default Re: Philips 819 line TV receiver.

http://www.cdvandt.org/CIOS-XI-1.pdf

http://www.cdvandt.org/TFT%20441%20TV%20Norm%201938.pdf

http://www.cdvandt.org/Band1Heft4Juli'39.pdf

http://www.cdvandt.org/Band1Heft5Aug39.pdf

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Old 22nd Jul 2018, 6:07 pm   #47
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Default Re: Philips 819 line TV receiver.

http://www.cdvandt.org/BIOS-867.pdf
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Old 22nd Jul 2018, 6:43 pm   #48
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Default Re: Philips 819 line TV receiver.

Quote:
Originally Posted by peter_scott View Post
Hi Peter,
on page 9 there is reference to the experiments on the high definition 1029 line system. Can you imagine what the video bandwidth will be if it is to be displayed on a 4:3 aspect ratio CRT screen. >14Mhz?

I'll have to brush up my German language to read the other technical papers.

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Old 22nd Jul 2018, 9:37 pm   #49
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Default Re: Philips 819 line TV receiver.

Hi David,

I have only glanced at the texts so far but I think they mentioned a direct link between iconoscope and viewing screen with a 20MHz bandwidth!

P.

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Old 23rd Jul 2018, 12:40 pm   #50
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Default Re: Philips 819 line TV receiver.

"I have only glanced at the texts so far but I think they mentioned a direct link between iconoscope and viewing screen with a 20MHz bandwidth!
P."

Achieving a flat response from DC to 20Mhz wasn't an easy task in those times.
From the September 1960 Practical Television magazine. "A distributed scope amplifier" The author of this article had a requirement for a oscilloscope amplifier that would amplify with a flat response signals from DC and up to and beyond 15Mhz. No big deal these days but even in 1960 using valves it was still difficult to design wideband amplifiers to this specification.

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Old 23rd Jul 2018, 8:59 pm   #51
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Default Re: Philips 819 line TV receiver.

The Philips 819 line TV set has been returned to it's owner who is very pleased with the results of all the work that has been done to this attractive looking set.

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