I was hunting at the local PC-recycle for a monitor that could be connected directly to my vintage C-128 natively without the usual converter (Gonbess + other) and cable mess. I could not believe my luck when I found a Sony CPD-1302 with Trinitron tube (good old particle accelerator!)
This monitor appeared in the ideal moment when the classic home computers from the 80ies were still around, but the PC revolution started - VGA was expensive and tied first to PS/2, most PC users had MDA, CGA or EGA (all digital) - or maybe PGA which was always a rarity given how high-end expensive it was (analog to be able to produce 256 colors). This monitor supports all of them:
- Analog mode (R, G, B, VSync, HVSync)
- Digital mode (3 different variations, from 4 monochrome "intensities" to 16 colors I, R, G, B, plus VSync and HVSync)
Looking at the CPD-1302 timing charts, it looked that the timing would match:
- Horizontal: 63.78us for CGA vs. 64us for TIM-011 video signal,
- Vertical: 50Hz for CGA (16.65us) vs. 55Hz (18.424us) for TIM-011.
Most importantly (where many vintage computer / monitor pairings fail), the CPD-1302 has a "smart" detection of VSync, extracting it from composite HVSync, or it can be fed directly.
Connection was simple:
|TIM-011||CPD-1302||Color (on CPD side reference pics below)|
|V0||one out of R, G, B, I||red, green, blue, intensity is white|
|V1||one out of R, G, B, I||red, green, blue, intensity is white|
Here are some experiments:
Connecting "I" for a color as expected rendered only 2 color image as the "intensity" digital signal is ignored. But the other color signal (green in this case) is recognized as "analog".
With the same I + G switching to "digital" mode, suddenly 4 "colors" appear, as expected. However one would expect black, and 3 shades of green but monitor shows the darkest green as brownish/grayish?
Now replacing the I+G with B+G:
As expected, this allows black, blue, green and cyan:
In all probability, CPD-1302 would work well with a "real" TIM-011, as it works in all modes (even analog!) with the FPGA implementation of its video circuit.
There was a problem with vertical sync - as seen above the frequencies are somewhat different. This caused flicker, until the image was adjusted towards top of screen. This made the picture stationary but lost few top line of the screen. Not a too big problem in text modes (as the action happens near the bottom of screen) but annoying for graphics or games.