Naive question about SCART connection on TV

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georgeo
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Naive question about SCART connection on TV

Postby georgeo » Sun Jan 28, 2018 9:43 am

Hi everyone

I recently picked up a new (to me) TV with better connectivity for plugging my old computers into: it's a UMC S16/3NG. It's a brand I've never heard of, but the display seems good enough for retro computing and it gives a clearer UHF output from my BB QL than my old TV.

I also notice it has a SCART socket, so wonder if I can switch to monitor output using a QL-to-SCART cable? The only thing I'm not sure of is the requirement (of the cable) for SCART RGB. Do all TVs with SCART support RGB inputs or only some?

Thanks in advance for any advice,
George.


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1024MAK
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Re: Naive question about SCART connection on TV

Postby 1024MAK » Sun Jan 28, 2018 10:09 am

Most TVs support RGB video signals on their SCART connectors. If there is more than one SCART connector, then you may find that only one supports RGB video signals.

The biggest problem with modern-ish TVs, is that they have automatic input detection. This uses the control signal pins on the SCART connector. If your TV has manual / user controls that can override the automatic system, then there should not be a problem. Otherwise, the only way to find out, is to try it. If you do have problems, there is a work-around.

A QL can produce a nice sharp and clear picture if a suitable lead is used. I use one I got from this eBay seller: retrocomputershack, item number 260814300633.

However, on the QL, the difference between TV mode and monitor mode, is the width of the visible display. The video output is too wide in monitor mode for most displays. If your TV has controls to adjust the horizontal picture position and size, you may be able to get the picture from the QL to fit in the width of the screen.

If not, TV mode still works fine when using RGB SCART.

Mark


QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
georgeo
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Re: Naive question about SCART connection on TV

Postby georgeo » Sun Jan 28, 2018 10:21 am

Hi Mark,

Thanks. I suspect my TV is a few years old. I can manually select the source and adjust the input size, so will give it a go.

Thanks again,
George.


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Cristian
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Re: Naive question about SCART connection on TV

Postby Cristian » Sun Jan 28, 2018 12:24 pm

I agree with Mark. Also I can confirm that some modern (and cheap) LCD TVs can not handle the QL Scart signal very well.
Anyway, the availability of the width adjustment option does not guarantees to get displayed the whole picture (you may see the lateral blank bands).


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Zarchos
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Re: Naive question about SCART connection on TV

Postby Zarchos » Mon Jan 29, 2018 12:53 pm

If I read this :
https://www.google.fr/search?q=sinclair ... oqeBzUv0UM:
I believe the QL doesn't output the (very often) necessary 5V to force the TV to AV RGB mode.
A solution is to bring this 5 V using a lead with a male USB connector (+5V to SCART pin 16 and ground is pin 18).
You will connect it to your PC, or even your TV as most of them have some USB ports, or a 'service' port which is USB (my P2270HD, Samsung, has that).
On the male USB connector side, from the outside, watching theconnector with the metalic bits at the bottom, ground is the extreme left, and +5V is the extreme right.

Hope this helps.
I use that for the Archies with 9 pin SUB D connector, as these Archies do not output this +5V voltage.

For the SCART here is what it looks like (from the soldering side) :


.............../
........../
.../
/................_20 |H-Sync
|_19 N.C...........|
|................_18 |ground USB
|_17 linked to 13..|
|................_16 |+5V USB
|_15 red............|
|................_14 | N.C.
|_13 linked to 17..|
|................_12 | N.C.
|_11 green.........|
|................_10 | N.C.
|_9 N.C.............|
|................._8 |N.C.
|_7 blue............|
|................._6 |audio left
|_5 N.C.............|
|................. _4 |audio ground
|_3 N.C.............|
|................._2 |audio right
|_1 N.C.............|
|_______________|

Note 13 and 17 are linked together (ground) and connect to the ground on the commie side.

PLEASE DOUBLE CHECK THIS IS CORRECT. I BELIEVE SO BUT DON'T TAKE THAT FOR GRANTED. I ACCEPT NO RESPONSIBILITIES WHATSOEVER IF SOMETHING GOES WRONG.
Last edited by Zarchos on Mon Jan 29, 2018 3:27 pm, edited 2 times in total.


Owner of various QLs including accelerated beasts, and also a happy Q68 owner ;)
Now porting SOTB to the Archies, to then port it to the Q68.
https://www.youtube.com/user/Archimedes75009/search?query=Acorn+Archimedes+Shadow+Of+The+Beast+%28100%25
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1024MAK
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Re: Naive question about SCART connection on TV

Postby 1024MAK » Mon Jan 29, 2018 2:53 pm

Pin-out of the QL video output DIN socket:-
Image(from http://www.dilwyn.me.uk Thanks to Dilwyn ;) )

If your TV does not have manual / user controls to set RGB input mode and to select the correct aspect ratio, then a DC supply is needed to feed the appropriate voltages to the control input pins on the SCART connector.

SCART Control signals
Pin 8
Status & Aspect Ratio up
  • 0 to 2 V → off
  • +5 to 8 V → on/16:9
  • +9.5 to 12 V → on/4:3
Pin 16
Blanking signal up
 / RGB-selection voltage up
  • 0 to 0.4 V → composite
  • 1 to 3 V → RGB
For pin 16, a suitable resistor can be used to limit the voltage if a higher supply voltage is available, such as +5V, +9V or +12V.

Mark


QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
martyn_hill
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Re: Naive question about SCART connection on TV

Postby martyn_hill » Mon Jan 29, 2018 3:26 pm

Slight clarification on Zarchos' ASCII drawing regarding the Sync pin on SCART:

Pin 20 is defined as the (full) Comp Video, when Blanking (pin 16) is around 0V, in which case the RGB signals are ignored.

With Blanking set to >3V, then only the C-Sync is expected/extracted from pin 20 and RGB are taken from their dedicated pins, which is what we want.

It is perfectly possible therefore to apply the full Comp Video signal to pin 20, and still have the colour signal derived from the dedicated RGB lines - the Comp Sync is then extracted internally to the display from the full Comp Video signal.

It can lead however to confusion as to which signal is actually driving the display at any given moment and if a full Comp Video (mono or full PAL) signal is indeed applied to pin 20 in RGB mode, some noise can end up there.

From a QL, in theory you may get a picture with any one of composite monochrome (QL pin 3), composite PAL (pin 1) or composite sync (pin 4 - potentially the better option) being connected to SCART pin 20.

My favourite cable is that available from the Sell My Retro site, though even then, at least one of my small LCD tellies seems to opt for Composite Video instead of RGB + C-Sync... I note from time to time that the display blanks out, and then re-connects - suggesting that an unintended mode change has been triggered (floating Blanking pin?)

One day I'll hack the cable to ensure that Blanking is forced >3V (there are apparently ways to get a suitable level with a couple of discreet components tapping-off from one of the signal pins, without need for a dedicated 5V source.)

.............../
........../
.../
/................_20 |C-Sync input -or- full Comp-Video input (determined by the voltage applied to pin 16 - Blanking)
|_19 N.C...........|
|................_18 |ground USB
|_17 N.C............|
|................_16 |+5V USB
|_15 red............|
|................_14 | N.C.
|_13 N.C............|
|................_12 | N.C.
|_11 green.........|
|................_10 | N.C.
|_9 N.C.............|
|................._8 |N.C.
|_7 blue............|
|................._6 |audio left
|_5 N.C.............|
|................. _4 |audio ground
|_3 N.C.............|
|................._2 |audio right
|_1 N.C.............|
|_______________|


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Zarchos
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Re: Naive question about SCART connection on TV

Postby Zarchos » Mon Jan 29, 2018 3:32 pm

I have amended my initial 'drawing' with pins 13 and 17 linked (as it is what I have in a cable I have just dismantled to make sure I don't post anything stupid).
My notes didn't have that, which is rather strange.

For the +5V which can appear to be too much, I believe (but please check) that the SCART standard has evolved over the years so that more than 3 Volts is in fact dealt with by the TV set.
Please research on this to be sure.


Owner of various QLs including accelerated beasts, and also a happy Q68 owner ;)
Now porting SOTB to the Archies, to then port it to the Q68.
https://www.youtube.com/user/Archimedes75009/search?query=Acorn+Archimedes+Shadow+Of+The+Beast+%28100%25
Martin_Head
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Re: Naive question about SCART connection on TV

Postby Martin_Head » Tue Jan 30, 2018 10:45 am

I don't think anyone's mentioned yet that you will likely need resistors in the R,G, and B lines. As the TV may require 1 volt signals, rather than the 5 volt signals from the QL. Also it may damage the QL if the RGB lines try to drive the low impedance (75 ohm) inputs of the TV without the resistors.


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Pr0f
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Re: Naive question about SCART connection on TV

Postby Pr0f » Tue Jan 30, 2018 11:09 am

I believe the RGB outputs are 1V video on the 8 pin connector - as there are resistors on the motherboard between the socket and the video ULA.



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