HP 5551 high voltage power supply

This power supply is adjustable between 0 and 1530VDC. It is able to supply a whopping 5 mA. Not very usable you would think but it was made for use with a fotomultiplier tube. That is a vacuum tube that releases an electron if a foton enters the tube. It has several stages and after the last one the electron is “multiplied” and a whole bunch exits the tube to trigger a counter. The tubes need a high voltage but draw not much current. The sensitivity depends on the voltage so that is why this psu is adjustable.

The supply has a 3 position switch labeled 170, 85 and 0V. It looks original on the inside but the numbers are not engraved like the rest.

This one is used atr the Technical University in Eindhoven  (inventaris number 0390, latst calibration was 1980.  Serialnumber 608-00217 option 01)

This is one of those instruments that should have a see through front panel. All those glowing 85A2 voltage regulator tubes are very pretty to look at.

Schema: 5551A SCHEMATIC

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