#Monitor Troubles!
14 messages in this thread
Scott, All monitors that have electromagnetic deflection, including
TV's, have a coil around the neck of the crt. This is what produces
the beam deflection for the display. The coil can be rotated around
the neck of the tube to make the image perfectly horizontal, in fact
this is one of the steps in the calibration of a monitor. There is a
clamp with a screw on it that needs to be loosened, then you can moce
the coil. Sometimes with age the coil will be a little bit stuck to
the neck, but this is normal. After you loosen the screw, turn on
your monitor and with only one hand in the monitor, carefully rotate
the coil. If your leary about the monitor being on, then keep it off
while adjusting it by trial and error. Aslong as you don't get near
the red high voltage cable AND! don't have some other part of your
body grounded, it should be no problem.
As far as why the image tilted, it's usually caused by jarring the
monitor or turning it on it's side or maybe it just slowly moved with age.
Bruce Patek.
– via Whap!
Thanks for the information Bruce,
I will open the case of my monitor and take a look, if it seems
straightforward enough I will go ahead and attempt the adjustment. I'll let
you know how it goes… Scott
Scott,
DO NOT SIMPLY OPEN YOUR MONITOR!!!! There's over 20,000 volts
inside and you can very easily KILL yourself.
Have someone that knows what they're doing work on it.
Don
Roger that Don………Thanks Scott
Bruce,
Unfortunately…or fortunately…depending on your viewpoint….the
manufacturer of teh 1950 chose to glue the defelction coil to the CRT using
lots of silocone adhesive. They can't be moved…I know…I tried real
hard on one and only got it moved by cutting away as much of the silicone
as I could. And even at that, I could only move it a very small
amount…but fortunately…it was enough.
Don
Don & all,
How about moving the whole CRT & yoke as a unit? I haven't opened a
1950, but it's possible with some monitors I've seen. There's a sort of
strap around the CRT that's screwed to the front faceplate. There was
enough slop in the strap's mounting hardware to rotate the crt a few
degrees.
Jim
Jim,
Yes, in some cases…that can be done. However, consider that if
the alignment was ok, and just sitting there…is no longer ok…then the
yoke or CRT probably didn't slip. What probably occured is that one of the
components in the deflection circuitry has gone out of spec.
Don
Don, I suppose it's possible that it was component aging. No doubt though
that it will be easier to adjust for the problem than find that out-of-spec
circuit.
Right…and usually that means a pincushion alignment rather
than a move of the CRT.
Raster rotation due to component aging or shift would require a
simultaneous and equal change in both the horizontal and vertical
amplifiers: very unlikely, since H is resonant and V is linear. This is
assuming that I understood the original symptom as being an overall
rotation, and not a vertical trapezoid distortion.
Also, a magnetic field near the neck can cause raster rotation. Fields
(as from speakers) nearer the face cause localized distortions, though.
Karl,
My understainding was the top was off, but the sides were ok…or
appeared to be ok.
A magnetic field near the neck should cause rotation…it should
cause distortion to one side or the other. The magnetic field should pull
(or push) the electron beam…but not rotate it.
Don
If the top and/or bottom were messed up but the sides OK, well,
that's a horse of a different RGB value! That can't be yoke rotation
either, however.
I beg to differ, however, on the nature of raster rotation as a
result of a weak field passing through the neck, a la earth's field.
We produce a monitor to compensate for raster rotation that results
from being used facedown into flight simulators' optics, because the
image rotates two or three degrees, depending on where you're located
on the earth. Admittedly, nearby equipment that could cause the same
thing would have to have a large field, not too close, with lines of
force in the right direction, but it IS possible. But if the fellow
doesn't really have a simple rotation, and has trapezoid or
orthogonality distortion(s) instead, the point is moot. I must have
misunderstood his description to begin with. Sorry.
Yes…a large enough magnet, far enough away (as you
noted…the earth) could rotate rather than skew the video. The
point being…that for all intents and purposes…the external
magnetic flux must be at equal strength at all points on the CRT (and
at the right angles) thus causing the electrons to attempt to spiral
along the field lines.
Karl,
Well…I typed that wrong…
"A magnetic field near the neck should cause.."
I meant to type:
"A magnetic field near the neck should not cause…"
Don