Hi fans / followers !
As I have announced in post #5 of this thread:
I need a small little B&W monitor which would fit into a 5" high attache case and be able to take the abusive, nonstandard video signal of the Apple-1 without throwing up.
In the past week, this project made a lot of progress despite I was completely trashed by the torturous toil and trouble to rake and bag the leaves on my property by myself. The usual guy who worked for me did not show up and did not answer the phone. Killed by the "vaccine" ? No willing to work for GTP ? For me it was bad to do all this myself, I had to empty half a bottle of "Famous Grouse" and popped a few Aspirin afterwards to be able to go to bed, long after midnight. In my age, and with worn out joints, nobody should rake and bag leaves, ever. It took me days to recover and I still feel it.
But my intellectual skills were not affected in any way. In just one week, I designed and developed a really fine circuit for making a B&W monitor out of an abundant and cheap to buy Chinese "TV & Radio" throwaway item. One of my target objectives was a stable and crisp picture and no horizontal PLL lock-in artifact despite of the nonstandard Apple-1 video signal.
I almost succeeded. Here are the pictures:
This glimpse in my lab shows the overall set up on my lab bench. You can see the "lab rat" and the Apple-1 clone making the video signal. The small notebook on the horizontal deflection power supply hosts the keyboard emulator featured here:
This is a close up of what is visible on the screen:
And this is the new electronics of the "lab rat":
Except for the picture tube, the deflection yoke, and flyback transformer, all the worthless and dubious "Chinesium" has been tossed into the trash can, where it belongs.
You may notice the resulting picture on the screen looks nice and crisp and centered, but my trained eye still can see some minor imperfections which need to be ironed out. I have also noticed some undesirable sensitivity of certain trim pots in the circuit: it's not easy to adjust them for a good picture. The dynamic range sucks. But with the "ATARI FLASHBACK" video game as a signal source, these problems are not seen and the adjustments are much, much easier and allow much wider margins to still produce a nice picture. This only proves that the nonstandard Apple-1 video signal is the culprit, and not my circuit design as such. I copied much of the circuit from the ST Microelectronics application notes and just recalculated a few components for the different vertical deflection coil. But ST does not give any hints about the video channel and cathode driver circuits itself (the TEA2037A IC is a horizontal and vertical deflection integrated circuit, and does not handle the Y = luminance channel). So I designed in the simplest Y channel circuit and retrace blanking circuits I knew and although they work fine with the ATARI FLASHBACK, they ain't great when they have to handle the "video signal from hell" (from the Apple-1).
So more work is required. Higher performance black level clamping and luminance (Y channel) circuits are required. But all the timing issues as such have been resolved. No "video fix" needed anymore.
Comments invited ! (Tell me if you would want to build one).