[Coco] CM-8 Monitor question

[camillus.b.58 at gmail.com]

You would need a good pattern generator, and a schematic so you can find the east-west correction circuitry. Probably some parts are changed value overtime, like resistors and caps.


Check first if there is no degaussing system build in. This basically takes the residu magnetisme on the tube raster away and improves geometry in general. On some monitors it is an option in the menu, but I doubt it would be on yours.


While you have it open I would change the high power vertical transistor, with a better equivalent. The ones in the units are working close to there bounderies and are bound to die.


good luck

cba








Sent from Surface





From: Robert Gault
Sent: ‎Sunday‎, ‎November‎ ‎16‎, ‎2014 ‎10‎:‎33‎ ‎AM
To: Bill Pierce, CoCoList for Color Computer Enthusiasts





Bill Pierce via Coco wrote:
>
> I have a CM-8 with a really sharp, clear picture with no "waves", lines or "sparklies", but it has one little thing that bugs me.
> The top right hand corner of the screen, starting from about half up, slowly angles slightly inward about 3/16ths of an inch at the top.
> The other 3 corners are perfect. Other than that, I couldn't ask for a better picture, though I often wonder "for how much longer?", as this monitor was bought the first year they came out.
>
>
> Is there any adjustment that can correct the dip in the picture?
>
>
> Thanks
>
>
> Bill Pierce

Gene would be an authority on this. There are no adjustments on the back of the 
monitor that can correct this, although it might look better if you increased 
the width of the image maybe also the height. There may be pots accessible on 
the back of the set for that.

This problem is cause by dying circuitry and incorrectly adjusted coils on the 
neck of the picture tube. There may be some magnets that can be repositioned and 
the coil itself may be moveable on the neck of the tube.
Since these adjustments would need to be made with the set powered up, it would 
be much safer to live with the distortion rather than getting electrocuted. :)

Robert


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