Today I pulled an old telephone system out of a store that was no longer using it. The one thing that caught my eye was this Harmer Simmons RD 219 Power Supply. It is a beast of a linear power supply with +/- 24 Volts at 4 amps and 5 Volts at 7 Amps.



Weighing in at 11 kilograms it would probably make a pretty good boat anchor. Here are some internal pictures.





Based on the date codes on the chips this is mid 1980s technology and it was probably considered pretty good quality. Taking the nominal ratings we have a potential 500 Watts of line power with an output of about 250 Watts. The unit still works but it has a moderate 60 Hz hum from the transformer. This unit is probably totally obsoleted by today's Switch Mode Power Supply technology. Some of the first SMPS were making their debut in the early 1980s but they were not very wide spread by the mid 1980s from what I can gather. There may have been other considerations for using a large linear supply to power telephone systems as well.


If anyone has any ideas for a good use for it let me know. In the meantime it will join the collection of things rated too cool to salvage.