TRS-80 Model III

From: Frank Palazzolo <palazzol_at_comcast.net>
Date: Thu Aug 8 13:02:01 2002

Sellam,

IIRC, it is possible to have the brightness adjusted so that you can see the raster, but
the contrast adjusted so that you cannot see the text.

If the contrast is the knob that is frozen or broken...then that might be the problem.
Strange, these pots tend to get a little dirty over time, but I've never seen one get that
bad off. Maybe they were exposed to some kind of contaminant. I've got 3 Model III's,
and the worst problem I've had was a bad VRAM chip.

Also, if you do have a scope, I remember there was a decent test point where the video
data can be tapped on it's way to the video circuitry. That way you can tell if it's a
computer problem or a video problem.

Good luck,
-Frank
Received on Thu Aug 08 2002 - 13:02:01 BST