Adjustable voltage source 10 – 50 V and adjustable current limiter 2 – 70 mA
This will do that







simulate this circuit &ndash; Schematic created using CircuitLab

This circuit IS casually REGULATED Voltage; you can use a 55 volt Zener to power the top of the 10Kohm potentiometer.

You can use a 1:1 transformer, if you can afford the heat dissipation in the Q1 device.
At 70mA and 100 volts across the Q1 (thus a LOW Vout), you have 7 watts to remove from Q1.

Probably use a Darlington NPN for Q1; if you do, then double the values of the two overcurrent-detect resistors.

You will have about 1 volt of ripple, at 70mA, using only 1 milliFarad of charge storage.

This circuit will have no high frequency spikes, unlike any switching regulator.