If doing an RGB mod you may notice jailbars on the image. This is caused by the gate Array chroma clock trace (SUB OUT pin 42) running near critical RGB signals.

This is a 4.434MHz square 4V clock signal (on a PAL system this was tested).

If using just RGB and not composite, the quickest fix is to just cut the VDP chroma pin 7th from the right. You will lose composite doing this.

Alternatively, cut the trace instead and re-route it to the CXA / MB3514 pin 6 (OSC IN) where it doesn't cross traces with any critical signals.

After this, there may still be faint partial jailbars that do not run up the full screen, in certain areas.

These are likely due to other clock noise where the RGB or CSYNC signals cross by Z80 or VDP clock lines.

I will work on reverse engineering that source of noise to provide a solution in the future. But they are generally very faint in 90% of situations so not noticable.