Re: Monitor problems

["Paul Grammens" <grammens@svn.net>]

"Frank Townsend" <ftownsen@iamdigex.net> wrote in message
news:sVxW8.5909$I02.5031@nwrddc04.gnilink.net...
> I've had a setback in my Apple II and other computer endeavors:  my
> venerable NEC 6FGP monitor is on the fritz.  The way this relates to Apple
> II is that this monitor has both D-sub and BNC connectors and a switch so
> that I can use it with my PC and Mac LCIII/Apple IIe card set up.
>
> The screen image is squashed in the vertical dimension to about 25% of the
> usual screen size.
>

Well... problems with the vertical ckt are easier to fix than problems with
the horizontal.  The vertical sweep is usually generated by a chip that has
a built-in heat sink. Usually just a piece of sheetmetal. It may be mounted
on another heatsink. It typically has distinctive "zip" pins, i.e. staggered
coming out the edge of the chip. Probably 16 or 18 pins, something like
that. Besides the vertical output, it  often has sync circuitry on it.
There are 4 wires coming out of the yoke, which is a coil on the neck of the
CRT. Two of them carry the horizontal sweep signal, and two carry the
vertical sweep. So the vertical chip is usually near where those wires
connect to the PC bd. Your problem is likely to be that chip, or possibly a
power supply problem with a voltage that chip needs. Could also be a bad
capacitor. Come to think of it, that's likely. What I often do is get the
part number off the vertical chip, look up the diagram for it, and it shows
the pinout. It usually has a pin that a capacitor is connected to, which
determines the sweep rate. I also try "Technician in a Can", which is what
we call freeze spray. Spritz the chip and local capacitors a bit and watch
the screen, see if the vertical size changes when you spritz (obviously you
have to do that while it's on.)  Figure out which part is causing the change
and replace it.

That's just generic info, may or may not apply to your NEC.  Good luck, and
of course be careful.
But as long as you stay away from the high voltage (fat wire going to a big
cap on the fat part of the CRT) and the power supply area, you should be OK.
-Paul