> On 23 Aug 2017, at 00:45, Don North via cctalk <cctalk@classiccmp.org> wrote: > > 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 >> >> > It is part of a switching power supply to boost the 9VDC input to 13.7V or > greater so that the 78L12 can regulate it down to 12V. > > L1 is dual purpose; it provides feedback to the boost switching regulator > oscillator (the tap) and is the main inductor for the boost supply generator.
Thanks for that Don, having re-read my original question I’m kicking myself for not spotting the whole ‘9V input’ thing. *sigh*. Cheers! — Adrian/Witchy Binary Dinosaurs - Celebrating Computing History from 1972 onwards
