Not possible to get stable image on A500+.

[PaulKlasmann]

Not possible to get stable image on A500+.

[PaulKlasmann]

Just a thought, how significant is that 3k3 resistor? If it was 10k would it matter? I cant see what its for besides tying GPIO18 to ground. It turned out that 10k Ohm resistors were in the 3k3 container! I can't see that being the cause of the problem.
Edit, changing from 10k to 3.3k made no difference at all, as suspected.
2nd Edit. Here are some pictures of the signals at CSYNC, CDAC and 7MHz at the Deniese socket with the chip and RGB2HDMI removed.

Are those waveforms and levels as expected or too low?

[IanSB]

Can you post a screenshot of the source summary page in the info menu

[PaulKlasmann]

I won't be able to do that now because I removed the flip flop ICs. It turned out I ordered the part ending in a 3, not a 4. The correct part has a clock input to clock the outputs so I think the outputs changed as soon as the inputs changed rather than all being clocked at once. The ones I had had a latch enable input in place of the clock input. I will update when I receive the new ICs and try the RGB2HDMI PCB again.

[PaulKlasmann]

I can confirm that the RGB2HDMI is now working correctly. The D-type flip flops were replaced with the correct clocked version and it works very well. Sorry about that! Should we delete this issue?