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The L we are interested in is the inductance that the
power supply presents to the power line. In the case
of the 2465, that is very low, in the tens to hundreds
of micro Henries. Insignificant, in so far as switch
life is concerned..

In the case of a scope with a big iron power transformer,
the inductance is the primary inductance of the transformer.
It is affected by the secondary circuitry, so it is often
easier to simply measure it.

In answer to question #2, use algebra.

Xc =f x C, -> C = Xc/f where Xc == |Xl|

For the case of XL = 100 ohms, C = XL/f

In answer to question #3, AC current needs a phase angle,
relative to AC voltage to calculate a DC resistance. It is
easiest to simply measure the transformer primary with a DVM's
ohmmeter.

In answer to question $4, the PTC is in parallel with the
resistor, not in series. The PTC tends to fail open with
age, which can cause the scope to burn up the parallel resistor.
Generally, though it will make the inrush lower, not higher.

Have you actually disassembled one of the switches to observe
the contacts? I find the biggest problem is not burning of
the contacts due to inrush, but rather the grease hardens,
preventing good contact.

-Chuck Harris

One note that needs to be mentioned, EMF is a high voltage
phenomenon, not a high current phenomenon. The current cannot
be higher than the operating current of the supply. The
voltage can rise to thousands of volts.

M Yachad wrote: