Hi
I have an Apple IIe where the color's are not correct. Please see my image below -
Of note, I've tried two different LCD's and different cables as well as a different IIe -
They ALL work as expected except for the problem IIe - so this is not a LCd/monitor/cable issue.
I've replaced the PAL/HAL - with a know good one and the problem persists . Any recommendations on what to look for here?
I've heard the Crystal on the board may be bad and I could remove and replace - but wondering if I'm going down a rabbit hole on that one?
I doubt it's a crystal issue, but it could be a 7 MHz video signal issue, or the fact that the signal isn't propagating with the correct amplitude or the waveform is distorted.
Crystals are cheap - like a dollar or two. But bad colour usually points to a bad HAL or bad IOU chip. Or the connections between the two, specifically the Vid-7 signal.
Well, it's not the HAL - as I've replaced it with a known workig one and I've also tried swapping out the IOU. As to the Vid-7 signal - without a scope what would you check?
Thanks!
Certainly could be a crystal operating on the edge. Try laying your fingers on the components near the ocsillator circuit to see if anything changes.
Otherwise, since it looks like your colors are 180 degrees out of phase, I'd say either the color burst or the video component might be flipped. The luminance looks OK so that rules out the VIDEO ROM, but the '166 at F5, the 'S109 at C1, or the 'S02 at B8 might be suspect. Less likely would be the 47pF cap, C32. The original Apple II had a 5-50pF trimmer in parallel with that. It's purpose was to specifically adjust the burst phase for this exact reason - to get the color hues correct.
@jeffmazur
Thank you - it's always the thing you doubt the least - it indeed is a short in the solder points at c32 - pushing it restores the color - looks like there is some soldering in my weekend. Very much apprecaite the feedback here.
SOLUTION: To summarize for future readers: Inverse colors appearing on Apple IIe, following replacement of IOU, HAL and other LS chips as outlined here, finally narrowed the color issue down to a solder joint @ c32.
Glad to help.
Yes, I was doubtful that the cap would go bad. But a bad solder joint, that's another story! In this case, probably an open connection; not a short.