7 Sep
1998
7 Sep
'98
9:17 a.m.
On Wed, 2 Sep 1998, Tony Duell wrote:
It's already 'useable' (I wrote the original message on the very machine
we're discussing) it's just that the distortion is noticeable. The
picture is probably only a couple of millimeters shorter on the left than
on the right, if there is even that much difference.
Considering the risks, and the amount of free time I've got, I've decided
not to do anything about this little problem for the time being.
Unless you think it's a sign of something worse on the way, in which case
a little preventative maintenance would be a whole lot better than
cleaning up after something goes kablooie in a major way. :)
--- Doug
Spence wrote:
my display appears to be squished slightly on the left hand side.
Can I fix that easily, without risk of electrocution?
--- end of quote ---
There are some adjustments you can do with plastic TV-tweaking
tools (even demagnetized metal ones distort the display when
they're near the board). The easy-to-reach ones are accessible from
the solder-side of the analog board (there should be a white
plastic sheet that tells you which controls are which). If those
Well, horizontal linearity (which is what you're asking about) is set by
the magnetically-biased coil L3. And AFAIK it's not adjustable. L2, which
can be tweaked, sets the width. The rings on the yoke centre the picture.
You might find that careful tweaking of width and centring will get a
useable picture. If not, look for defective components in the L2/L3 area
(in particular that 3.9uF cap I mentioned). Whatever you do, don't tweak the DC voltage preset
on the analogue board
unless you know what you are doing. I normally set if to get the +5V line
spot-on, but I have not idea if that's the official thing to do.
I'm not sure it's set correctly as it is. When I got the machine it had a
clip-in 512K memory expansion in it, and I was told that the voltage was
probably tweaked to accomodate this board.
However, the machine wouldn't start up with the memory board in it, so I
removed it. But I never tweaked the voltage on the analogue board.
As soon as I get the appropriate parts to fix the memory board, it's going
back in.
-tony
Doug Spence
ds_spenc(a)alcor.concordia.ca
http://alcor.concordia.ca/~ds_spenc/