(fwd) Model 4 video problems

From: Benedict Chong <bluesky6_at_ix.netcom.com>
Date: Sat Jul 26 10:39:58 1997

Can any expert out there help me with this? Thanks!

In comp.sys.tandy, bluesky6_at_ix.netcom.com (Benedict Chong) wrote:

%I just got a Model 4. When I turn it on, the disk drive will spin but
%there's no video.
%
%When the video brightness is increased, I can see a large rectangular
%green area where the video would be.
%
%Instead of video characters, there are lots of zigzag lines across
the
%screen, with more on the top of the screen than towards the bottom.
%The entire screen is stable and does not flicker or move around.
%
%It has been a good number of years since I last played with this kind
%of video (built a 6502/6845 terminal in the mid 80s) so I can't
%remember what problem would cause this type of symptoms.
%
%When I remove the video connector (after opening up the machine), the
%screen loses the vertical hold. I guess that would mean that the
%vertical sync and circuitry is working.
%
%Could the problem be due to the monitor circuitry or a problem with
%the Horizontal Sync generation?
%
%Would appreciate all/any pointers.
%
%Ben
%
Received on Sat Jul 26 1997 - 10:39:58 BST