Early SECAM televisons

[dominicbeesley]

Hello all,

I'm working on a new colour "standard" for NBTV, this time based on the French SECAM system - which I beleive may be easier to implement and more tolerant of poor communcation channels.

Anyway I'm having a first go using modernish components, but was wondering what the early SECAM television decoders looked like. Were they all transistorised or where there some all-valve or hybrid decoders.

I'd love some circuit diagrams of early SECAM sets, but these are hard to come by in the UK. So do any of the French contingent have any info?

Any help, as always, greatly appreciated

Dom

[Jean-luc]

Hi Dominic,

Here is the circuit diagram of the first color TV that I repaired when I was a student.
It's the easiest that I found, all transistors.
An interesting particularity of these early Secam circuits: The Y signal was modulate to The CRT by the 3 cathodes strapped and the color (B-y R-y V-y)by each whenelt (G1).
Congratulations for your NBTV/SECAM project, beautiful tribute to the French technology

Jean-Luc

[dominicbeesley]

Merci Jean-Luc,

Definitely some interesting stuff in there already, and some short cuts that will save on parts!

Any more diagrams would be welcome!

I think that method of driving the CRT is called colour difference array (CDA). I've thought about it for the current project, Y to grid and difference signals to cathodes. It would mean remaking the tube base but might be worth the effort!

I have a quick question about SECAM sets (I've never owned an old one). Do the contrast and colour controls work like on a PAL/NTSC set. This must be difficult to arrange the colour being FM?

SECAM has always fascinated me, I always thought French TVs looked more colourful and the interferences patterns different to PAL sets.

Thankyou very much Jean-Luc

Dom

[Klaas Robers]

The very first SECAM set I am aware of was a all tube receiver. In the beginning days of european colour-TV the research lab of Philips made several tens of the K4. (what happened wit the K1, K2 and K3 I don't know, I never heard something of them).

The K4 was an all tube receiver, most of them had a circular picture tube of which at the top and the bottom a part was hidden behind the front. The K4 was started to be an NTSC (625 line) receiver and the idea was to do a field test with them. They were "lend" to important Philips managers and technicians. Philips had her own colour-TV transmitter and -studio from where test tarnsmissions were done. This was first in NTSC, but I don't know for how long (short).

Then the receivers were modified to PAL, after Walter Bruch had defined his standard. I heard that one set was rebuilt to SECAM and test transmissions were done in SECAM as well. This SECAM set was called the K5, but only one existed ever. All tubes.

Then the K6 was designed and this first normally produced TV was transistorised for the receiving and decoder part, while the deflection part and the video amplfiers were all tubes.

The K7 and K8 were also partly with tubes, the difference was the deflection angle, 90 degrees resp. 110 degrees.

The K9 was the first all transistor TV (except the picture tube of course).

[dominicbeesley]

Thanks for the info Klaas,

I'm assuming K7, K8 were PAL only are they related to the G8 as sold in the UK or was that developed seperately?/Do you know any model numbers for the SECAM variants by Philips?

Cheers

Dom

[Klaas Robers]

No I don't.

However I know that our Philips TVs for SECAM were in fact normal PAL TVs. Extra was a simple SECAM to PAL converter that made a PAL-compatible signal from the incoming SECAM video. The converter was just one IC and SECAM TV's could also receive PAL transmissions. And that was what we sold in France.

The strange thing is that in France all TV production was done in PAL. Also the distribution of the progams (micro wave links over the country) was done in PAL. In the TV transmitter was a conversion circuit that converterd the PAL signal into SECAM, just before the modulator.

So in reality France had a PAL system with a very small piece of SECAM in between.

[Jean-luc]

You are right Klaas, since 1983 all europe TV sets production must be PAL/SECAM by the euro AV connector (PERITEL), before that, all french TV brands made monostandard sets.
A small chronology of french Philps color TV sets:

1968: TVC3 , first SECAM PHIPS TV on the french market, color circuits with valves(video amplifiers) and transistors
1970: TVC4 , color and sound amplifier circuits solid states, time bases with valves
1972: TVC5, all solid states , color decoder with integreted circuits
1974: TVC6, 21” models
1976: TVC7,TVC8 first philips models with PIL CRT (without convergences controls)
1981: TVC11, last only SECAM sets
1983: TVC12,TVC13(square CRT), PAL/SECAM sets
1985: TVC 14, TVC15 first automatic cutoff control, end of TVC chassis series
All of these SECAM color TV sets were concieved and made in france with “La Radiotechnique (RTC)”

For Dominic , Secam pictures of the Schneider TV discribed below and a TVC3 PHILIPS I have restored recently
I have the TVC3 and TVC4 diagram circuits, if you want, I can scan Theme this weekend, an if I have enought time, perhaps I' ll try to post a diagram with english comentarys.

Jean-Luc

[dominicbeesley]

Thanks for the pictures Jean-Luc, they look absolutely superb!

Any more diagrams would be really helpful, and some english translations for some of the notes as well! I've made a bit more progress tonight I've started building a first go at a SECAM decoder.

I now have the B-Y and R-Y FM decoders working well enough for a first try and the line by line switching, well it works 50% of the time!?! I've started trying to make a delay line, so far without much luck.

I'm trying to make the delay line (2.5ms) with a speaker and a microphone. Unfortunately the microphones and speakers I have aren't really good enough so I'll need to find something that works well at around 15kHz....

Dom

[M3DVQ]

I'm trying to make the delay line (2.5ms) with a speaker and a microphone. Unfortunately the microphones and speakers I have aren't really good enough so I'll need to find something that works well at around 15kHz....

interesting idea using a mechanical delay line, very old school
have you looked at ultrasonic transducers? don't know how easily they can be modulated with an analogue signal but they can certainly handle the high frequencies, and they'll have a matched response also.

[dominicbeesley]

Thanks for interest,

Yes I've looked at a few different ideas. Ultrasonic are plan D, plan A was some condenser mics and speakers I had in the junk box but they look like a dead duck. Plan B is ear-buds, Plan C those piezzo transducers from birthday cards.

The ultrasonic idea is probably the best but will require converting up to a frequency of 40kHz with a fairly tight bandwidth.

For now I might just cheat and make a digital delay line...

Cheers

Dom

[Jean-luc]

I 've just finish to scan these manuals in PDF , electric circuits and block diagrams.
I look forward to see the first color pictures on your CRT monitor!

Jean-Luc

[dominicbeesley]

Thanks Jean-Luc,

They are all very useful and will help with doing thing properly. I like these French circuit diagrams - especially the block diagrams which give references to the components!

Last night I made a delay line using a PIC micrcontroller as a temporary measure while I try and get the rest of the circuit working. This is 213*8 bits where the FM carrier is fed in as a square wave and read out delayed by 2.5ms.

I now have B-Y and R-Y being decoded correctly and will try and make a simple colour matrix to make R, G and B later today and so will hopefully have a colour picture though it will probably look pretty awful!

If that works then I will have to sit down and design the circuit properly, so far I have just being trying things out as I go along which means it is certainly not perfect!

Dom

[Lowtone]

The strange thing is that in France all TV production was done in PAL. Also the distribution of the progams (micro wave links over the country) was done in PAL. In the TV transmitter was a conversion circuit that converterd the PAL signal into SECAM, just before the modulator.

So in reality France had a PAL system with a very small piece of SECAM in between.

This is so true. Even most camcorders were in PAL. And in the 80s & 90s they sold PAL>SéCAM transcoder in oder to record onto VHS-sécam-only.

The first VHS players were only in SéCAM until the early 90s.
In later model you can convert SéCAM in MESéCAM, or PAL.

The real SéCAM mode on VHS is really awfull !
Two years ago i found a VHS from 1996. There was a TV programm in SéCAM with horrible colours, and something i've done in PAL 8mm>VHS. The colours of the PAL footage were really nice. Really amazing compared to SéCAM onto VHS.

Unfortunatly most recorder were in SéCAM mode, and I think most people didn't use the MESéCAM mode, or PAL mode.

My last SVHS recoder gives nice pictures with the PAL mode

[Lowtone]

I don't know if Time Base Corrector can work in SÉCAM.
Mine does PAL only.

But i have an S-VHS player who can transcode SÉCAM ( and even NTSC ) to PAL.

I plugged it in the TBC. The picture is not perfect, but it is better now