Linards Ticmanis wrote:
I wonder what would be the easiest solution to delay the activation of the transistor? I thought about adding a someting like a capacitor (220uF maybe) in between B and Ground.The capacitor would be charged through the 4.7k in Graphics mode and then upon the switch into text mode it would slowly discharge through the resistor again. So both switching directions would have a delayintroduced. The mean voltage in mixed mode should be high enough to keep the transistor inactive at all times then, so the quartz gets its working voltage and stays happy.
To answer my own questions (maybe for the benefit of future Google users?), it did work fine. Color is delayed about a second after switching to Graphics mode, but that is fine with me as long as things work.
Also I moved the quartz's fine-tuning adjustable capacitor (5-30 pF or so) to the outside of the case and connected it wiht some wires - that makes it possible to adjust the fine-tuning when the picture starts to wobble from the interference of the mainboard color clock and the PAL card's. Since getting rid of this depends on very exact tuning of the quartz, it has to be readjusted once in a while.
-- Linards Ticmanis The Master said, "The business of laying on the colors follows the preparation of the plain ground."