[Coco] Magnavox 8CM515 / Commodore 1084 monitor

[Rogelio Perea]

Sometime ago I got a Commodore 1084 monitor for my CoCo 3 setup. As far as I
know this is the same monitor as the Magnavox 8CM515, correct me if I am
wrong on this assumption.

This by far works better than the CM-8, except for a minor glitch on the
composite side of the operation... for some reason the brightness level of
the display is really different between the two modes: RGB-TTL and
Composite, the later being the lower one. A friend of mine had a Magnavox
8CM515 back then and I do not remember having this problem, we could switch
between the two modes with no other difference than the definition of the
image on screen, right now I have an OK display with the RGB input but
brightness goes down on composite, have to adjust the front bright knob to
compensate up when going composite and then adjust down when going back to
RGB - on RGB  the brightness control is uauslly set half way so I'd say the
CRT is still very well in its useful life.

Lacking the service manual of the 1084 it seems to me that the problem must
be some internal adjustment in the monitor PC board tha affects only the
composite input... any ideas of where should I start looking for in order to
fix this minor problem?

Thanks!

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-=[ Rogelio ]=-