Good evening folks, I recently obtained a Simplex master clock "type 946-2 Op" from a local auction house here in the UK. Externally, it seemed to be of good quality, but upon closer inspection I was disappointed. The internal movement was a cheap, quartz type with plastic gears as fitted to budget clocks for the home in the late 1970s. This was fitted between a pair of pressed aluminium plates with thin, pressed brass gears running in plastic bushes pushed into the plates. Turning my attention to the electronics, I noticed badly-placed components on the circuit board and removed the latter for closer inspection. There were numerous poor-quality soldered joints so I re-soldered the complete board, pressing on the components to make them flush with the board and clipping the protruding tails short on the underside. It was then I noticed a glaring design error. Those of you who know some electronics will be familiar with zener diodes as voltage regulating devices. These require a series resistor to limit the current flowing through the device, but in this case, the 33 V diode was connected directly across the main reservoir capacitor with no resistor. Not surprisingly, the diode had overheated and gone open circuit which put around 50 Volts on the series regulator and taken that out too. Thankfully the transformer survived even though the 3.15A secondary fuse had no chance of blowing when the transformer could only deliver 250mA. I thoroughly checked the board and there was never a place for the series resistor and have posted pictures showing the diode Z1 connected directly across capacitor C1. I have since modified the board and added the necessary series resistor (last picture). I also noticed that instead of the normal rechargeable battery used on many master clocks during power fails, a large electrolytic capacitor had been fitted. This would have been useless as a backup during power fail as it would only have held the circuit for a few seconds. There is no charging circuit on the board, just a huge (computer grade) electrolytic capacitor whose inrush of current when initially charging might blow the underrated 1A bridge rectifier. I had assumed that Simplex was a quality manufacturer, but was wrong in this case as there are design faults and sloppy manufacturing. My query is to ask if anybody else has seen this type of clock before (type 946-2 Op) and wondered how long it would have lasted before failing. Perhaps it was a prototype for testing before going into the manufacturing process for market? Any thoughts please as I'm a bit puzzled? Were Simplex a quality manufacturer at this time? Thanks.