If you already have variable output DC power supply, than all you need is the resistor to limit the current through D.U.T. and the meter hooked up across the D.U.T.
Or build this portable tester.
I built one years ago using a small surplus 60VAC transformer and a 10mA constant current source. Was quite useful to test zener diodes or to use as a simple 10mA current source. I built it to handle a 80V zener that we used that would fail every so often, but it was also useful to test high voltage rectifier diodes that had a 20V or so forward voltage drop. Reverse voltage testing on those was with a 10kV insulation tester, which would show any gross faults, but which was not much use as the equipment in question ran at 30kV on the anode. At least the 10kV allowed us to trouble shoot without burning up anything else in the test phase. It was way to high for any other use, as it would happily kill any mains rated cabling it was attached to, and would make things like sockets arc over internally.
Built a simple one years ago for testing zeners from a blacklisted supplier, the only supplier (Arrow) that had that value. One of the production staff had to sit there all day testing zeners , felt sorry for them but they said is was relaxing. about a quarter were within tolerance. Anyway power supply a suitable watt resister (could just use a couple in parallel) and a bench meter does the job.
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A simple cheap SMD airflow tool is a handheld gas soldering iron without the iron :. is a selective hot airflow which can be regulated by turning up/down gas, also no onerous air lead. I have replaced many components without damaging them or the solder pads all within seconds... can also be used as a soldering iron & on heat shrink
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