It's a little switching power supply. It steps up the 9V input voltage
to something a few volts greater than 12V to feed the 12V regulator.
If your 12V is correct, it is probably working.
Rob.
On 8/22/2017 4:30 PM, Adrian Graham via cctalk wrote:
Hi folks,
Failing Atari PSU aside I remembered a question I had ages ago but never posted
about the power circuit of another 80s home micro, the Enterprise 64. This
machine is powered by a 2A 9V unregulated PSU and internally there’s a pair of
7805s and a 78L12 to smooth things out.
There’s also a small transformer coil in there too (L1 on the following
schematic) and I’m not entirely sure what it’s for. Here’s the schematic of the
original circuit, any enlightenment gratefully received since I have an
Enterprise 64 with a dead coil :)
http://www.binarydinosaurs.co.uk/ep64PowerRegulators.png
<http://www.binarydinosaurs.co.uk/ep64PowerRegulators.png>
Cheers!
—
Adrian/Witchy
Binary Dinosaurs - Celebrating Computing History from 1972 onwards
