Diy questions cadet rgb encoder

Category: Unknown · Tags: cadet · Posts: 3

#1 — lst555 · 2025-09-11

hello, i’m new to video diy and i was trying to make the rgb encoder on a veroboard. i skipped the sync generator and replaced it with a LMH1980 to provide for the blanking, hsync and vsync. (found this in another thread here) i have 2 monitors and on my mini aliexpres car screen i get a lot of flickering and sometimes and image and on the other i do get a better result but very glitchy. it’s kind of cool somethimes, but not workable. the hsync and vsync of the LMH1980 seem to work because i get stable lines from and oscillator.

these are some questions that came up:

• is it possible to skip the sync generator and use a LMH1980 to extract hsync and vsync from a video signal and use that to sync the ad724 ?
• can the burst of the LMH1980 be used as a blanking signal for the cd4063 ?
• i’m confused about the 2 crystals in the schematic. i read in the ad724 datasheet that a logical high in the stnd input selects ntsc and a 3.579 545 mhz crystal in the fin input. so in the schematic the 5v goes through a 10k to the crystal. shouldn’t the crystal be grounded for it to be selected ?

some pointers or insight are very much appreciated.

thanks for reading,

lieven

#2 — phosphenes · 2025-09-18

I wouldn’t skip the sync generator, its designed to work in tandem with the RGB encoder and will give you lots more flexibility for internal / external sync in the future. I believe there’s a thread that working on resolving the issues with getting hold of the crystal for the sync generator.

#3 — lst555 · 2025-09-23

Ok, thanks for the suggestion phosphenes ! I’ll look into that.