[Coco] New circuit video coco2

[Luis Fernández]

Thank you for that clarification.---------------------------------------------------------------------------------

> From: zippster278 at gmail.com
> Date: Wed, 11 Mar 2015 13:12:51 -0500
> To: coco at maltedmedia.com
> Subject: Re: [Coco] New circuit video coco2
> 
> Oh yeah, that too.. :)  lol
> 
> Mostly due to generation of regulated 12v on the board I suppose,
> allowing a little more flexibility in adjusting the amplitude of the final output.
> 
> Though the data sheet circuit works well too.
> 
> The only way I can see to really improve on these would be using op-amps
> instead of transistors after the 1372 for a simplified layout, which I will probably
> do for the MC10 and any CoCo1 adapter.
> 
> - Ed
> 
> 
> > On Mar 11, 2015, at 12:47 PM, Joe Grubbs <jsgrubbs at hotmail.com> wrote:
> > 
> > And Ed, didn't you also notice that the circuit you're using (Tandy) was better than the application circuit in the 6847 datasheet?
> > 
> > 
> >> From: zippster278 at gmail.com
> >> Date: Wed, 11 Mar 2015 12:12:10 -0500
> >> To: coco at maltedmedia.com
> >> Subject: Re: [Coco] New circuit video coco2
> >> 
> >> Hi Luis,
> >> 
> >> Though there are some simple transistor driver circuits out there,
> >> they seem to only drive some composite inputs.
> >> 
> >> Implementation of the MC6847/MC1372 pairing varies by CoCo model.
> >> 
> >> Those with the 1372 in the RF box have an oscillator frequency tuning circuit
> >> connected to the RF tank inputs, where a DC offset voltage is needed to generate
> >> baseband composite.  This would be all CoCo2’s.
> >> 
> >> CoCo1’s do generate baseband composite from the 1372 before it is sent to
> >> the RF box, but there is a transistor amp circuit in-between.  The signal could be
> >> tapped here and levels adjusted with a simple driver circuit.
> >> 
> >> The boards I put together connect directly to the MC6847 and generate proper baseband
> >> composite, along with handling sound, and put it into one convenient output jack.
> >> They are based on Tandy’s own composite output solution, found on educational model
> >> CoCo2’s.
> >> 
> >> Like anything with electronics, there are several ways to a similar destination, this is one way.  :)
> >> 
> >> - Ed
> >> 
> 
> 
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