User Programmable Standards Converter

[Spot Wobble]

Regarding your post, Jeffrey, about UHF probably never being used for 819-lines, the part of Frank's 9-90UM manual reproduction referring to the 'French TV Standard' on UHF must have been the 625-line service in France (which commenced in the 1960s, I think). And this 625-line service in France was the one that eventually adopted SECAM colour (as 819-lines was monochrome only, I understand).

Regards,

Francis

[`FRANK.C]

Thanks Frank - out of interest, how difficult would it be to get a (correct) video OUT signal (from the VHF tuner) from a 9-90UB, please?

Hi Francis
I have not tried it so don't know.
There is some good information on getting video out from a 9-90UB on this thread over on the UKVRRR forum. It don't look too difficult.

Frank

[ppppenguin]

The service manual for the CVM90, the monitor version with a box on the side, is available here on GVR. The circuit isn't very easy to follow but it's only a few transistors, Rs and Cs.

[`FRANK.C]

I managed to get some time in the last while to spend on this project.
I have successfully combined the down converter and up converter. It will now generate any number of active lines from as ridiculously low as 4 to around 800.

I have added adjustable sync level. It can be adjusted from 20% to 50% in 5% steps. I think this should cover most needs.

A while back I added independent right and left crop.

I have also added vertical shift. The active lines are by default added before the frame sync. So if the number of active lines are less than to fill the screen the picture will appear towards the bottom of the screen.
Vertical shift inserts blank lines between the end of the active lines and the following field sync. This can be used to centre the picture vertically if doing letter box etc. It can be also used to insert the blank lines before the frame sync that is needed in the 819 standard.

I have also completed and tested 25Hz field output. I was actually able to test it on a 625 line monitor running at 50Hz field rate. The output of the converter was 625 lines at 25Hz. The monitor locked solidly to the 25Hz sync and if I used 288 active lines or less I would get a good but flickery image.

Photos below of 20 and 50% syncs.
Frank

[`FRANK.C]

Photos of crop and vertical shift. The monitor is set to under scan.

The first is how it would appear as default if there is not enough lines to fill the screen.
the second uses vertical shift.
The third uses vertical shift and crop.
the fourth is crop only.

Frank

[`FRANK.C]

Some photos of various no of lines at 25Hz
I lengthened the front and back porch as much as I was able to. To make them a little squarer.

They are 16, 32 64, 120 and 220 lines.

Frank

[Murphyv310]

Excellent work Frank.
I'm watching this with interest.

[Jac Janssen]

Impressive results Frank!

Jac

[Freya]

Your incredible work amazes me as with all your designs.

[`FRANK.C]

Thanks for all of your comments.

I spent some time today writing some files to program the modulators and a lot more time trying to correct the mistakes I made in them. Nothing to show for all that yet. I need new files as it will be the microcontroller that will be programing the modulators and not the FPGA as in previous Hedghog's

Frank