[Coco] CoCo 3 to RBG...

[Steve Batson]

Gene,

thanks for the in depth technical detail. I do have some electronics 
background, but not in video and it's been a while ;)

I guess my question is, if I had a good Multisync monitor with enough 
range, might it work with just building the cable?

----------------------------------------

From: "gene heskett" <gheskett at wdtv.com>
Sent: Sunday, July 10, 2011 6:38 PM
To: coco at maltedmedia.com
Subject: Re: [Coco] CoCo 3 to RBG... 

On Sunday, July 10, 2011 09:19:04 PM Steve Batson did opine:

> Interesting idea Gene, if it was that simple, why would there be
> converters? Your TV may have something my monitor does not. Would be an
> interesting test though. :)
> 
Older CRT type monitors have the horizontal output stage whose transformer 

is optimized for 31khz, and slowing that down, even to the high 20 khz 
range will usually saturate the ferrite core of the transformer because of 

the extended on time per scan line. When that occurs, 95% of the current 
limiting inductance disappears, and the currents can then rise several tens 

of amps per microsecond which has two effects, one on the output transistor 

whose time to shut off at the end of the cycle in lengthened considerably 
by the high current flow, and on the ferrite in the transformer, which if 
it exceeds its curie point while that heavily magnetized, will never 
recover, turning Austenitic(non-magnetic) forever. End result is that half 

the circuit (& 90% of the cost) goes up in smoke before the fuse or circuit 

breaker has a clue.

Modern digital LCD tv's have no such scanning iron limitations, so their 
ability to follow a slower than normal signal is usually a pure function of 

the clocking circuits phased locked loop oscillators lock in range. Some 
will, more likely won't, but my much newer 42" Visio still will, working 
nicely when fed either component from the dvd player, or composite ntsc 
from her movie camera.

That is why I would say it is worth the time to make the cable & find out.

[...]

Cheers, gene
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