[Coco] Converting CoCo 3 to USB power

[Rocky Hill]

 And like Rick said, it's more complex than you would think.
    On Sunday, January 28, 2024 at 01:06:16 PM EST, 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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