Re: Color trim pots on MB?

[mjmahon@aol.com (Michael J. Mahon)]

Ernest asked:

>What are the color trim pots on the motherboard for? Would this be for
>something like Hue and Contrast, etc. or is for somthing like video timing
>sync?
>
>I never really thought about it before, until I noticed that one of my clone
>motherboards is missing these little Color Trim pots. Now I'm curious to
>know what they a were used for. Were they really needed, and what might be
>the effects of having no (or broken) CT pots.

They are probably not pots, but variable capacitors, used to adjust the
phase of the color burst signal, and thus "hue".

Since the burst is generated directly from the Apple II clock, there
is little need to adjust its phase, and these variable capacitors 1) were
not cheap, 2) were not easy to stuff on the board, 3) were hard to clean
safely after wave soldering, and 4) required human adjustment during
manufacture, and so were eliminated from the design.

If there is actually some deviation from "perfect" hue in the Apple II
video signal, it is easily corrected by the user adjusting the hue of
the monitor, anyway.

-michael

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