I noticed a step-down transformer, two large capacitors and a full wave bridge rectifier inside the UK1400 but obviously this is only part of the conversion and regulation process so although the UK1400 supplies unregulated DC, the regulator circuits in the ZX81 could make the larger supply unsuitable for a particular reason, so I thought I'd ask never having seen a ZX81 PSU.1024MAK wrote: ↑Mon Jul 18, 2022 1:59 pm There are no transistors in any of the Sinclair 9V PSUs as used with the ZX80, ZX81, ZX Spectrum 16K/48K/+, 128K or the +2 (grey). All these computers use a 7805 (or higher current version) series pass voltage regulator (which is also often described as “linear”).
I got on a Electrical/Electronic principles course a long time ago but only got as far as trying to get to grips with Thevenin, Kirchoff and Fleming before I had to drop out, unfortunately and I've not so far managed to catch up with my studies.