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Old 17th Sep 2017, 7:03 pm   #1
Pieter H
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Join Date: Sep 2017
Location: Waalre, Netherlands
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Default Hi, happy to join this forum

Hi all,

I'm very happy to join this forum, after having read through some of the very long and very informative discussions.
I'm probably a bit of an oddity in this community, because more interested in the history of the technology than in actual set restoration. (That might come later if and when I have more time, because I do have a modest collection of old TV's and radios). And then preferably technology history with which I have some "personal" bond. Having worked with Philips (and later NXP) for 30 years this is clearly the core of most stories so far.

My interest in vintage TV's has always been there, but my first activity was triggered by the old home-built TV of my father, dating back to 1948 when he worked with Philips in Eindhoven. Although I did interview him many years ago on what exactly he had done and the background of his TV, all that was still very scarce in terms of facts and data. So the first thing I did was trace back the history of the EQ40/EQ80 valve, which was one of the key components in his set. This has resulted in a dedicated web page on that valve:
EQ40 and EQ80 history

While doing that I discovered that both the EQ40/80 as well as my fathers set were being developed in the midst of the first Philips TV developments, which I have then further researched leading to these two pages:
How Philips developed television pt1
and
How Philips developed television pt2

I've now started on the history of (Philips) TV tuners, which will be the main topic for questions soon! I hope the members of this forum will be able to help me with the British aspects of that, which often means Mullard. I look forward to the discussions!

Cheers, Pieter
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Old 17th Sep 2017, 8:31 pm   #2
Radio Wrangler
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Default Re: Hi, happy to join this forum

Hello, and welcome!

I think you might create some very interesting discussions.

David
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Old 18th Sep 2017, 5:49 am   #3
peter_sol
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Hello
May I assume that those valves apart from their bases are the equivalent of the later EH90 which Pye used and called the circuit a quadrature detector.
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Old 18th Sep 2017, 7:15 am   #4
raditechman
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Hi Pieter,
Thank you for those very interesting Phillips television articles. It must have taken you considerable time to prepare them. Much appreciated.

John
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Old 18th Sep 2017, 9:12 am   #5
ukcol
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Quote:
Originally Posted by peter_sol View Post
Hello
May I assume that those valves apart from their bases are the equivalent of the later EH90.......
Look at the data sheets from the National Valve Museum it seems this is not so.

The EQ80 is an enneode have 3 control grids and 3 associated screen grids. The EH90 is a heptode having 2 control grids and 2 associated screen grids.

EDIT: I note having had a quick look at the FM detector circuits using the EQ80 that only 2 control grids are employed, g1 being connected to the cathode, so in this application the EH90 and EQ80 work in similar ways.
Attached Files
File Type: pdf eq80.pdf (365.4 KB, 19 views)
File Type: pdf eh90.pdf (277.8 KB, 14 views)
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Last edited by ukcol; 18th Sep 2017 at 9:20 am.
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Old 19th Sep 2017, 9:05 am   #6
Pieter H
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Hi Peter and Colin,
in my view the EQ80 and EH90 were fundamentally different valves. The EH90 is a classical heptode, which, when used as an (RF) mixer, does the classical analogue multiplication and associated down-conversion. (Whether the signals are in quadrature is then first order irrelevant).
The EQ80 is a coincidence or phase detector, requiring preferably clipped or almost digital input signals. It then operates as phase detector (therefore the Philips name "phi-detector"). This is a fundamentally different function than a mixer. One can also better see the EQ80 as two stacked pentodes that perform an analogue "OR" operation.

Cheers, Pieter
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Old 19th Sep 2017, 10:51 am   #7
ukcol
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Hi Pieter,

Thanks for the explanation.

I am more familiar with the EH90 as an FM detector of 6MHz intercarrier sound in TV receivers rather than in its mixer application. I (think) I understand though from what you have said that the EQ80 is fundamentally different in its operation.
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Old 27th Oct 2017, 1:49 am   #8
Synchrodyne
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Although in its locked-oscillator FM demodulator application, the EH90 heptode was acting as a quadrature coincidence demodulator. This is not the thread for a detailed treatment, but, early efforts by Zakarius and Kalmus to develop an FM quadrature coincidence demodulator based upon a single multigrid valve failed from lack of adequate and signal-independent limiting. Okrent saw that a control grid that followed a screen grid could provide good limiting, and proposed a limiter-demodulator using a valve that contained a pair of such combinations. This led to the Philips enneode. At about the same time, Zenith took a different approach, designing the mechanical layout of the valve to provide strong limiting at two control grids. Its gated beam valve (6BN6) was an ersatz dual-control pentode. Slightly ahead of both of these, Philco apparently combined the locked-oscillator discriminator with a quadrature demodulator in a single heptode (FM1000). The Philips EH90 circuit was a reincarnation of the Philco circuit, albeit it different in detail.

Quote:
Originally Posted by Pieter H View Post

While doing that I discovered that both the EQ40/80 as well as my fathers set were being developed in the midst of the first Philips TV developments, which I have then further researched leading to these two pages:
How Philips developed television pt1
and
How Philips developed television pt2
Excellent sites thanks very much. The early history of the 625-line system is somewhat obscure, so commentaries on it are always welcome. Also welcome is the information on 1950s French 819-line receivers, such being hard to find elsewhere.

Cheers,
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Old 27th Oct 2017, 9:41 am   #9
Peter.N.
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Hi Pieter

Welcome to the forum. There is plenty of history on here and quite a few of us were around when it was made, I started in the TV trade in 1954 and many of the now 'vintage' TVs we sold new, I have even worked on prewar ones - but I wish we hadn't scrapped so many!

I went to Evoluon in Eindhoven a couple of times but I don't believe its there now, pity. We had a colour demonstration film of it on BBC, I saw it so many times I felt quite at home there.

Peter
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