Hello,
Just got back from the workshop.
Over the weekend I replaced all the electrolytic capacitors in my A600 (will do the A1200 next weekend) and this has removed some of the spurious noise seen on the composite video output. It is still not perfect though.
Whilst measuring the composite video output of my A600 on the scope, I noticed a problem, the scope had trouble locking to the composite video signal. As a sanity check I used a cheap CMOS colour camera, the scope locked fine and I could easily trigger on any particular line. With the A600 I could not.
It looks like the equalising pulses from lines 1-3 are not quite correct, this appears to be causing my scope not to lock on. I need to borrow some equipment to verify my theory here, this will take a few days.
There are numerous ways of creating a better video signal but I/we need to understand the problem first.
In my day job, which involves developing video systems for aircraft we have numerous non-standard video types. With a few tweaks I have modern LCD panels synchronising to all sorts of video, it helps when you can programme the decoder input stage though.
@Ferix,
You're in Tokyo a busy place, hope you enjoy the break.
For the MSX and the Sinclair Spectrum +2, were you also trying to use RGB mode?
I don't suppose you fancy removing the back cover from the TV and taking some photos?
@Photon,
From experience you can get LCD TVs to sync to non-standard video, especially in composite mode easily. The domestic VCR outputs a Vsync signal that has +/-1us of jitter, for PAL/NTSC it should be +/- 37ns, yet the panel locks on. I built the PIC Tetris board, for test purposes
and this has equalising pulses missing and a large sync jitter, again LCD and CRT TVs locked onto it fine.
If I can work out what I need to do to make an adaptor PCB, it will be done.
Will report back in a few days.
Ian