[Coco] Tandy CM-8 Monitor Viewable Size

[Richard E. Crislip]

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.