I picked up some high-voltage power supplies via eBay ages ago (from a friendly retired high-voltage power supply salesman, funnily enough, such a job title does exist!) and re-discovered them this weekend, stored in a box in the shed.
I was curious to see what’s under the cover.
This is supposed to be a really nice, very low-noise, stable power supply that can be adjusted between 0-2kV at up to 2mA. Its primary use case is for powering photomultiplier tubes (such tubes are optical sensors that can detect very low quantities of photons), which happens to need a high-quality supply. The power supply could be used for other purposes too. I don’t have a use-case for it currently. I believe this device is new and never used, although it was made a very long time ago! (The date code is 9649, i.e. about 27 years old!).
The output of the supply appears on an RG59-B/U coax cable. On the input side, all the connections are neatly labeled on the metal enclosure, which is great. A card edge connector is used for the input 24-30V power, as well as an optional potentiometer (to adjust the voltage) or a 0-9V control input, and there is an output 0-2V connection for attaching a panel meter.
One screw is all it takes to un-hook and lift off the very nice metalwork:
Unfortunately, the high-voltage section is potted. I’d love to see what’s inside, but it’s not worth destroying such a useful item. The top of a pot-core transformer is visible, but not much else!
There may be a flyback circuit, but I cannot say for sure. The two TO-220 devices together in the photo above are TIP29C NPN transistors, which are likely part of it.
The photo below shows (as is apparent from the date code anyway!) that the design is old, and the PCB looks hand-drawn. This particular power supply is still a manufactured product from Spellman HV Electronics Corp today, model PMT-20C, but I’ve no idea if the board layout has changed over the years.
Here is a photo of the underside, I have labeled the connections:
I have not used this device yet, but I’ll report back once I have!
Thanks for reading.