My install didn't work at first so I did some tests with a multimeter. +5v to ground showed 2k ohms.
From ground; DP2, and DP5-7 had no resistance, the rest were only 8k. EXT0-3 showed 10k. DB0-7 all showed 8k.
I put the PPU back in the NES and it seems fine.
Back to the NESRGB20, after much more difficulty removing PPU from the expansion board than the from my front loader NES motherboard I did the tests again.
Now +5v to ground has 5k ohms. DP0-5 now have about 16k except DP5, which still has no resistance. EXT0-3 and DB0-7 have no change, all 10k and 8k.
Does this give enough info to determine where the fault is or what caused it? Can it be fixed, or do I need to buy another? If I broke it, how do I avoid it in the future?
Thanks for your help