[Coco] MC-10 Composite mod woes

[Zippster]

Hi Steve,

I still have a few modulator replacements for NTSC MC-10’s available.

They are $30 plus shipping.  If you're interested, send me an email with your
shipping info and we’ll get you set up with one.

- Ed


> On Aug 13, 2017, at 9:52 PM, Steve C. <towmater at gmail.com> wrote:
> 
> I just had my be-hind handed to my by my MC-10 when I tried to do a
> composite mod. I tried a double-2n2222 mod that's been around for decades,
> but I think that older CRT screens may have been more tolerant, as two LCD
> screens with composite inputs failed to recognize anything coming from the
> MC-10.
> 
> I tried another set of transistors and tried with the main rf pin 12
> connected to the old rf circuit and also with it pulled up. Then I read the
> specs on the mc1372 and it states that the chip will output composite if
> the rf-tank is bypassed and a diode is placed between 1372's pin 13 and 14.
> To finish that circuit pin 12 is also connected to a +7V + resistor. I
> cleverly used some resistors to take 9V down to 7V off of the 7805's input,
> and magically brought the whole computer to its knees. Bad idea.
> 
> So I don't want to go through too many of the alternative amplifier designs
> without knowing if they are also not tolerated by LCD TV's. I thought a VGA
> solution would be nice and it looks like one for the Color Computer is
> under development, and also saw that Zippster38 had done a modulator
> replacement, but couldn't find any order info, from the description it
> seems that perhaps only a handful were made.
> 
> I returned the RF output to operational in the meantime, if anything just
> to make sure that the 1372 still functioned after all of the abuse, though
> using the computer with RF is virtually impossible as the noise is
> unbearable.
> 
> Any suggestions are enormously welcome.
> 
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