[Coco] Tandy CM-8 Monitor Viewable Size

[Gene Heskett]

On Wednesday 19 August 2015 11:06:31 Richard E. Crislip wrote:

> On Tue, 18 Aug 2015 22:31:38 -0400
>
> Gene Heskett <gheskett at wdtv.com> wrote:
> > 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
>
> I watched Dad blow one up while he was assembling a Heath Kit
> amplifier. It did sound like an M80 or a 30 - 6 going off inside the
> house. Fortunately its guts pepper his face, not his eyes, that would
> have ended his professional flying days.

Been there, done that. :)  The ceiling of that house, if it still stands, 
has a dent from the top of a 1" can that is about 1/8" deep in the 
plaster.

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>