For some reason I'm not getting any colour output from my II+ clone. The monitor (composite input) is attached to the video output on the back of the computer. Other than that there are no other issues with the video (it displays fine, but only in black/white), and everything else appears to work on the computer.
So I looked up the Applebox diagram (which illustrates what each IC does) and I've swapped the following ICs, alas without any difference:
74LS02 (B13) color ref
74LS11 (B12) color burst
74LS51 (C13) color decoding
74LS32 (C14) video blanking
I intended to swap F14 (74LS259) as well, but didn't have another one to try out. I also haven't replaced transistor Q3 (J14) close to the video level trimmer, but I suppose since video in general works it's fine.
Where else could the problem lie?
Before getting my II+ in fully working condition I had a problem with the keyboard not responding (see this thread). It turned out that a circuit trace had corroded away, but of course was very easy to fix once I tracked it down (thanks to people in this forum!). Could the reason be likewise here?