[Coco] Tandy CM-8 Monitor Viewable Size

[Gene Heskett]

On Tuesday 18 August 2015 21:05:02 Ron wrote:

> Hello,
>
> I have a Tandy CM-8 monitor that seems to be working fine, however,
> the actual "viewable" area on the screen seems much smaller than it
> could be as there is quite a bit of black border around the whole
> picture.
>
> Is this normal for a CM-8 or is there an adjustment that can be made
> (internally) to increase the picture size as there doesn't appear to
> be user controls to do this?
>
> Thanks
>
> -Ron

From a C.E.T.:

You may be able to widen it a bit, but that would probably wind up 
pushing it to let out more magic smoke.

If you look its innards over, and know what an electrolytic capacitor is 
supposed to look like, I'd bet a Miller64 there's a dozen or so that are 
either dried out because the antifreeze has all leaked out, leaving a 
white residue where the leakage took place, or just as bad, the top has 
bulged and perhaps split at the scored lines in the alu top.  Those are 
there to prevent its blowing up like an M-80 if the ESR goes too high & 
it gets way too hot.

Bulged/split tops, or evidence of leakage means it needs to be replaced.

Replacements should have a very low ESR, and rated for 105C service.
ESR=Equivalent Series Resistance.  Usually measured at 50 to 100 KHz, by 
a special meter few techs have as its around a $200 bill, and for new 
capacitors, s/b well under 1 ohm.
Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>