[Coco] Converting CoCo 3 to USB power

[Robert Emery]

If you install a Pepper board, Q1 is no longer used. The heat sink
physically blocks the pepper board, so removing the whole thing just makes
sense.
 In my latest live-stream (1/20) I converted another CoCo 3 to DC (PD 9v).
There are chapter markers.
 This one has not yet had a Pepper board installed, so no cassette or
serial I/O, otherwise working fine.

Bob
LaCoCoStrangiato is my channel

On Sun, Jan 28, 2024, 12:06 PM Lee via Coco <coco at maltedmedia.com> wrote:

> Patrick,
> So you think he's done something more than just cut the 3-pin connector
> cable from the power supply he removed and connect the 3 wires where he cut
> them to the +9v (he demoed it in the video with a 9v battery) and ground of
> the tiny USB PD board?
> -----
> Lee
>
> On Sun, Jan 28, 2024 at 8:33 AM Patrick Ulland via Coco <
> coco at maltedmedia.com> wrote:
>
> > The CoCo supply is more complex than you’d think. Starts easy, a
> > transformer rated 8 volts either side of center tap. Runs about 10 volts
> > under light load. Those 3 to connector.
> >
> > The two (+/-) are rectified and sent to the SALT (or pepper
> > replacement). The salt internally regulates these to become the +/-
> > power rail for analog and zero crossing work – cassette, bitbanger,
> > joysticks. Low current supply done.
> >
> >   The raw +8VDC also goes to pass transistor Q1 – what many call a
> > ‘voltage regulator’. SALT has the 5v reference, and switches Q1 at the
> > right speed to keep the + side of C15 a perfect 5v, which feeds the main
> > 5v rail.
> >
> > I don’t see from this video what Bob’s done with Q1, maybe hidden under
> > tipped over c29? Else there are more secrets;-)
> >
> >   -ricku
> >
>
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