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Re: Apple IIgs Monitor Going Bad?
Tempest wrote:
Although there is more than one way to interpret "jump a little", it
sounds like the vertical sweep generator (or is it "jumping" from side
to side?) is drifting with temperature.
It's jumping vertically.
Try adjusting the vertical hold control (in back) to restore stability
after it warms up. Then see if it isn't stable when first turned on.
If you find the "sweet spot" where it's stable both cold and warm, then
you're golden. (If there is no such spot, then a component in the sweep
circuit needs replacing.)
I'll try fiddling with it tonight. Is this a common problem with IIgs
monitors? Would the vertical sweep generator going bad explain the
headaches? It's not just a slight jump in the image now and then
(although that does happen), I swear it also starts to get hard on the
eyes as well.
Vertical frequency drift can be a problem in all older (analog)
monitors. They are, after all, just like TV sets. ;-)
Occasional (slight) vertical jumping can easily cause headaches.
As you adjust the control, you will note that when turned in one
direction, the picture "scrunches" a bit, but doesn't "flip" unless
it's turned very far. If turned in the other direction, you will reach
a point where the picture will roll down slowly before jumping to lock,
then roll again slowly, etc.
The ideal adjustment is achieved by letting the monitor warm up
completely (say, an hour), then adjust in the "slowly rolls down"
direction until it slowly rolls down. Then adjust it back the other
way until it locks solidly, providing a slight extra travel in that
direction.
Then turn off the monitor and wait a couple of hours for it to cool
completely. Turn it back on and observe the raster. If it is stable,
then it will remain stable at least until its as hot as it was when
it was adjusted, and your problem is solved.
If (in Summer, for example) it should start to run warmer, you may
need to repeat this process.
If, within a year or so, it needs readjustment even though the
operating temperature has not shifted, it means that a component
in the vertical oscillator circuit is drifting as it ages, and
will eventually need to be replaced (when the adjustment range is
exhausted).
-michael
NadaNet networking for Apple II computers!
Home page: http://members.aol.com/MJMahon/
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