Henry Kolesnik wrote:
Do you have GloBar resistors in the UK? These are high cold and go lo
with current. they used to be very popular in TVs over here.

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Haven't come across these ,at least not under this name. I understand
they are Power NTC resistors .
Wonder if these would heat-up quickly enough within the 'start-up
period' to prevent a current surge.

In the meantime I have tested my Astron RS-50A PSU.
When switched on at 230 V AC (50hz) it sometimes trips the circuit
breaker and is rather heavily buzzing ,but when the voltage is increased
to that value from zero with a variac the buzzing level is lower .
No-load current is 0.69 Ampere , Power is 28 watts as measured with a
multifunction energy monitor.
Having had the unit running no-load for 1 day the buzzing level is
acceptable with the transformer being luke warm.

I now intend to include a simple soft start unit ( 12V relay with 1-2
seconds switch-on delay which shorts a series 50 Ohms-50W resistor (from
junk box) in the primary transformer winding line.

Comments on quality of unit :
-Insulation between primary and secondary winding of transformer looks
rather 'iffy'

- Output connection posts are of the type normally specified for 30
Amperes max.
I shall replace these by more heavy duty posts.

Having done that I intend to test the unit on rated capacity with 4
(approx 1 Ohm) resistors made of iron fencing wire , put in a bucket
with water.

Frank GM0CSZ / KN6WH