Dear fellow vintage TV enthusiasts,
Last year I was able to get my hands on a couple of TV sets that support the French 819 Line standard, so naturally I wanted to generate some signals for those sets. Among the sets I have are a Sony TV9-90UM the French version of the TV 9-90UB and a Radiola (Built by Philips) TV originally built for the Belgian market. This latter set is in mint condition and the CRT is like new.
I ruled out using an up-conversion from 625, because I wanted to get an idea about the true resolution of this vintage HD format. So the best approach in my mind was to use a PC to generate the required signals from 720p and 1080p footage.
Luckily I had come across Kat Mantons threads regarding this subject matter which helped me a lot in getting my project up and running. I would like to thank Kat for sharing this information regarding the mode lines for 819, this is much appreciated!
Modern Linux systems can be made to generate odd resolutions very easily nowadays. Here are the steps I took to get my Linux Mint system running on an HP 8440p laptop computer to output 738i i.e. the French 819 line system.:
Step #1) First we need to find out the internal designation of the VGA port. In order to do that we need to open the console and input this command:
xrandr | grep -e " connected [^(]" | sed -e "s/\([A-Z0-9]\+\) connected.*/\1/"
This will yield some output like:
LVDS1
VGA-0
Hint: You can copy the above by using the usual "control+c" keys. In the console you need, however, to use "Shift+Control+v" to paste.
The first is the internal LCD panel of my laptop, the second (VGA-0) is the VGA port. Please take note that the VGA port will only show up in the list if something like a monitor or adapter is connected to it. Here "VGA-0" is just an example, depending on the PC system used this may have other numbers.
Step #2) Now we need to generate the new resolution using Kat Mantons mode line. We key in this command in the console:
xrandr --newmode "819_TV" 29.3203 1152 1168 1240 1432 738 744 745 819 -hsync -vsync interlace
and make it known to the VGA port by using this command:
xrandr --addmode VGA-0 819_TV
As can be seen we use the internal designation of the VGA port "VGA-0" obtained in step #1 for this second command. If everything went well the VGA output should now have an 819 line signal at its output. This will show up as a second monitor to the right of the current display. In order to play a video through the VGA port simply drag the the player window to the "monitor" on the right and put it in full screen mode. I usually use VLC and set its aspect ratio to 2,21:1 to get the correct format of 16:9 footage on a 4:3 screen.
Please take note that the new resolution is not permanent and will have to be re-configured after a re-boot. In order to make this change permanent the easiest way is to edit a file named ".profile" that can be found i the home folder. Just add the two lines from step two at the bottom of the file.
Hint for the Linux novice: Please take note that this is a hidden file and you will only be able to see it if you hit Control+h on the keyboard. Any file or directory in Linux that begins with a "." will be hidden.
In order to obtain a good quality 1Vpp video signal from the VGA port of my PC I built a circuit that will entirely run off the 5V supplied by the VGA port on pin #9. The circuit itself runs on 3,3V and provides 2 outputs with 1Vpp into a 75Ω load. Since not all PCs and graphics adapters provide a 5V output powerful enough to run the circuit which needs around 16mA I have made provisions for an extra power input via a micro USB port. A blue LED lights up if the supplied voltage is high enough to power the circuit i.e. above 4.2V.
I use the THS7314 video amplifier to drive the outputs and amplify the signal to the required 1Vpp. A simple matrix generates the luminance signal from the red, green and blue signals. The H and V sync signals are fed into an XOR gate to turn them into a form of composite sync. This is not fully system compliant but my TVs work very well with this signal. In order for this to work with only a single 74HC1G86 XOR gate the vertical sync from the VGA port has to be inverted. This can be achieved by simply changing the mode line at the end. instead of having "-vsync" there it should be changed to "+vsync" that's it. Here is the complete mode line:
"819_TV" 29.3203 1152 1168 1240 1432 738 744 745 819 -hsync +vsync interlace
Here is the circuit diagram and a few images of the board I have designed in KiCAD. It mostly uses SMD components.
The project data for this board is available in KiCAD format. Please send me a PM or mail and I will send it to you.
In order to get the signal onto an RF carrier I used a modified version of my system A modulator that I had introduced here in the past. This uses only one crystal to generate the vision carrier and a simple LC circuit for generating the difference frequency between vision and sound carriers which in this case is 11,15Mc. I was able to use an original FM IF filter for the oscillator that generates the 11,15Mc intermediate carrier. This intermediate carrier is then mixed with the vision carrier signal and depending on the French channel to be generated the difference or sum frequency needs to be filtered out giving the sound carrier. The sound carrier generated by this method then goes to an AM modulator that is fed with the audio signal. I shall be posting the final circuit of my system A modulator with the French modification here in an upcoming post.
I was lucky to find a 56,57Mc crystal in my junk box which is close enough to the French channel F3 at 56,15Mc. Since channel F3 is an odd numbered channel the sound carrier in this case is above the vision carrier by 11,15Mc i.e. at 67,30Mc or in my case due to the slightly off crystal at 67,72Mc. It is worth noting that even numbered channels have the sound carrier below the vision carrier in the French system, while odd numbered ones have it above the vision carrier. So I tuned the sound carrier filter in my modulator to 67,7Mc and was able to get sound and vision in glorious 819 lines on my TVs...
To be continued...