[Coco] MC-10 Composite mod woes

[Rietveld Rietveld]

I just use a 3ft RG59 F female connector to RCA male plug cable instead of the TV switch box.   My display is very clear

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  Original Message
From: Steve C.
Sent: Sunday, August 13, 2017 10:52 PM
To: CoCoList for Color Computer Enthusiasts
Reply To: CoCoList for Color Computer Enthusiasts
Subject: [Coco] MC-10 Composite mod woes


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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