So later thay year (1965) the PZ3 was introduced. On the upright part of the chassis was mounted a power transistor, with other components mounted on its legs. There was a tag strip for the output. The circuit had two smoothing capacitors.
The circuit is unusual as it was not stabilised but used a gyrator as a smoothing element. A gyrator is an electronic inductor - the circuit is described on 4QDTEC, where it is used as a tuned circuit. This resulted in a very smooth output that is ripple-free, so no mains hum, but not stabilised.
Unfortunately Clive specified 1/16 inch (1.6mm) thick aluminium for the chassis. This was not thick enough to support the heavy transformer so many of these units got badly bent in post.
The PZ3 (if I recall correctly) had no circuit board and two large capacitors, so it was not very cheap to produce. It was soon replaced by the PZ4 which, although mounted on a similar chassis, had only one reservoir capacitor but was stabilized. The components were mounted on a PCB which made production easier and removing one larger expensive reservoir capacitor made production more economical.
The gyrator was a "clever" idea introduced by Martin Wilcox who had joined Sinclair Radionics in February 1965. However Clive Sinclair wrote a letter about the gyrator principle which was published in Wireless World, March 1967 [page 40 (140)]. You can get a pdf of this Wireless World, March 1967 from American Radio History. Page 47 (147) also announces Sinclair's Z120.
As there is so little information on the PZ2 and PZ3 I would appreciate contact with anyone who actually has one!
Document URL: diy.torrens.org/Sinclair/pz/pz3.html