[UK-CONTEST] 12v PSU trips?

[Clive Whelan]

Hi list

Very slightly off topic, but very important in my contest station.

For reasons with which I shall not bore thee, I swapped my IC7400 from the
run radio (left) to S&P ( right). This entails changing PSU also, from a
Daiwa conventional mode, to a Nissei switch mode unit, which has performed
impeccably for about three years when powering either of two TS870s. To cut
a long story short, the Nissei is not switched off itself, but powers up
with the big switch in the shack.

Several other small devices share this PSU. I found by trial and error that,
if the ICOM is connected to the PSU in this scenario , albeit itself powered
OFF, it trips the PSU about 75% of the time. Clearly no significant amount
of power is used by the ICOM in the off position-possibly zero- so I wonder
what is going on? The only way I can get the ICOM going on this PSU, is to
physically attach the plug to the rear, WHILE the PSU is switched ON, and
this causes no trouble, but do it the other way around, and she trips.
Clearly this is not a viable way to proceed!

I can switch the PSUs around, but in due course both will power ICOM units.
Is this something anyone else has experienced, and if so what might be the
cause , and more importantly the solution? Are switch mode units more
susceptible to tripping than linear mode, and is this possibly due to
imbalance on the pos. and neg. lines, just like a domestic RCB?

Advice welcomed


73


Clive
GW3NJW