Can someone identify this colour de-coder board.

[ctc15]

Hi
Can someone identify this colour de-coder board.
It is a three colour standard PAL SECAM NTSC decoder.
I would like to use it for a universal decoder to RGB.
Thanks Keith

[bobbyball]

Possibly B&O?

[Red to black]

Yep definitely B&O, don't know which model though, possibly MX4000 chassis

[Max Ripple]

Yes,it's B&O,but I can't make out the labels to identify it more.
Can you clarify please?
It's a multi standard decoder and video output module,but its controlled via data lines from a central microprocessor depending upon B&O software.
Not sure how you will be able to use it for anything else,alas?
Nick

[TonyDuell]

Since the main ICs appear to be Philips, data sheets for them are likely to exist. Said data sheets will explain how to control them (probably via an I2C bus) and you could probably use an Arduino or similar to do that.

[Red to black]

It will be controlled via an I2C bus.
The difficulty will be in interfacing it.

We need more detailed pictures to identify it further, it does look to come from the MX4000 chassis but I can't be 100% certain at this stage without better close ups of the labels attached.

[cmjones01]

The other issue with using it as a general purpose colour decoder is that TV colour decoder chips tend to need some signals from the rest of the set to work properly. In particular, they frequently need a flyback pulse and/or sandcastle/burst gate pulse from the line timebase, so making them work without the rest of the set can be tricky. When I did this I had to build part of a line timebase in order to get the decoder to work.

Chris

[Red to black]

That is also true of course Martin, this set of chips will definitely need a sandcastle composite pulse to work too, plus a system ident to even know which system it is supposed to be decoding, all of this would have would have been incorporated within the sets original design, a difficult task no doubt about it.

[TonyDuell]

If it is from the MX4000 chassis then it doesn't look too hard to use. The service manual is available from Elektrotanya. The board uses standard Philips ICs that you can get the datasheets for. I've found them online with no problems.

The only use of the I2C bus is to control an 8-channel DAC chip (TDA8444) which then controls analogue voltages for contrast, saturation, etc. I know the data sheet for that chip is available because I've used it. Or you could whip it out and feed suitable DC voltages into the points it drove.

Yes, you need a sandcastle pulse, but there are deflection control ICs that will give you that.

[marceljack]

Originally Posted by Red to black

That is also true of course Martin, this set of chips will definitely need a sandcastle composite pulse to work too, plus a system ident to even know which system it is supposed to be decoding.

Regarding the standard identification (PAL, SECAM or NTSC) this information is a part of the composite video signal applied at the input of the board (subcarrier burst).
The TDA4650 recognizes and switches automatically to the standard of the signal at its input.

[Red to black]

Not always, some relied on which band was selected to decide which colour system was selected, this may have applied to earlier chipsets in use.

Now of course with these later chipsets that may not be required and may in fact be automatic, as we in the UK rarely saw true multi standard sets as a whole I am not qualified to comment.

[marceljack]

Originally Posted by Red to black

Not always, some relied on which band was selected to decide which colour system was selected, this may have applied to earlier chipsets in use.

Now of course with these later chipsets that may not be required and may in fact be automatic, as we in the UK rarely saw true multi standard sets as a whole I am not qualified to comment.

What is not automatic (and in practice cannot be reliably automatic) is the TV standard selection and switching (channel bandwidth, video polarity, audio carrier modulation type and vision/sound spacing) but as soon as the vision signal is demodulated you get a Cvbs video which contains the colour identification information which is automatically processed in multistandard colour decoders since the mid 70s (first integrated PAL/SECAM implementation with TBA540/TCA640/650/660 chipset from Philips semiconductors).
In the analog days, this type of multistandard TV (PAL BG / SECAM LL') was rather common in border regions of France, Belgium, Germany and Switzerland.

[Red to black]

Hi Marcel,
As I said multistandard sets were comparatively rare in the UK, and besides even less people had any signals to run them on, for the vast majority of us they were only a passing curiosity.

There was a very niche market here, mainly the TV DXers and the odd Archivist/film collector and possibly the few standard/format conversion firms.
A few of these sets were privately imported too.

[bobbyball]

I recognised the panel because I have quite a few B&O sets - mainly of the MX/LX series. The later models in these ranges were multistandard by this stage and sold throughout Europe so it made sense for them to do all the various colour standards - sometimes only via the SCART socket(s) of course.

[Red to black]

Hi Bobby,
B&O sets in general were not particularly Thick on the ground up here in the NE either

[ctc15]

HI All
Thank you for your information.
l have a number of TVs most PAL and some NTSC,SECAM. l would to use
this panel to check my coders.
l have some TDA1180 TV horizontal processor chips which can supply the
sandcastle pulse.
The TDA8444 DAC can be removed and pots used to supply the 0v to 12v
analogue voltage.
Thanks
Keith