[Coco] RF to VGA Converters...

[Gene Heskett]

On Sunday, January 11, 2015 10:48:27 PM 
univax!gatech!destroyer!trantor!kandur did opine
And Gene did reply:
> Either that, mine is a 2014 product,
> or your monitor needs higher level inputs?
> 
> Kandur

The monitor at the time was an escapee from the weather set at the tv 
station, formerly used as a draw on it with a finger display as it also 
had a touch screen coating on the crt face, and it was not as transparent 
as a normal screen, so it did take a higher drive the GB just couldn't 
deliver.

And of course the green gun was getting puny like they all did. It might 
be adequate to drive the LCD unit I'm using now, but I've removed the 
synch combiner it needed from the coco now.

My gime is extremely sensitive to its supply voltage, and if I was so 
lucky as to find a trimpot that could turn that old XT supply thats 
running everything, up a hundred millivolts, my gime would be a much 
happier camper.

The shacks bean counters saw the ferrite beads the design engineers put 
in the board traces for noise suppression as an un-needed expense, so a 
10 ohm resistor was used in production.  Bridging that with a 1/4" piece 
of wrapping wire raised the video output levels it could deliver by about 
50%, but they still are below standard .714 volts at peak white.  That 
resistor was only dropping its supply voltage from 4.98 to 4.94 volts.  
The actual supply input to the board, over at what was formerly the 
emitter of the pass transistor, is 5.04 volts.  Anything up to 5.25 volts 
would/should be a Good Thing.

Its basically a round tuit problem. I've managed to miss-lay mine. :)

> Sunday, January 11, 2015, 7:38:21 PM, you wrote:
> > On Sunday, January 11, 2015 10:30:21 PM
> > univax!gatech!destroyer!trantor!kandur did opine
> > 
> > And Gene did reply:
> >> Seriously Gene,
> >> I have to turn down the contrast and brightness on my
> >> Samsung SyncMaster 2693HM (1200x1920) LCD monitor
> >> to get a decent 80 column picture from the GBS-8220.
> >> 
> >> Kandur
> > 
> > Humm, I wonder what the difference is...  A later production unit? 
> > Mine is circa 5 or 6 years old.
> > 
> > Cheers, Gene Heskett


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>
US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS