Thank you to all those who have responded - I certainly appreciate it. Here's
some general comments in reponse to suggestions that I've received.
I normally run the Omni on a 961 supply that I picked up a couple years ago.
When I started having Herc problems, I tried putting the Omni back on the 9420
and found that it no longer worked, as I described in the original post.
Here's a little more detail on the voltage trip problem. When the Herc is
switched on, the Overload light comes on immediately and the relays for the 4
supplies do not stay closed. The overload light and VCC fade away after 4-5
seconds as the caps discharge. The over-voltage SCR on the Herc's distribution
board remains tripped (since it's powered by the always-on supply) but since
the Overload light is powered by the switched voltage, it does not stay on.
The voltage trip problem started with occasional trips while I was talking.
They became more and more frequent, and now it does it almost evey time I
switch on the Herc. I'm guessing one of the supplies is going unstable, but so
far haven't been able to tell which one.
With a digital scope, I have succeeded in capturing a momentary spike of about
20v on the switched voltage line that occurs at switch-on. It seems to decay
toward the normal supply voltage but, since the whole thing shuts down, it's
hard to tell. I wish I could scope the voltage of each p.s. while the Herc is
running but I can't if it won't stay on. I think testing the individual
supplies is the next step - I just gotta figure out a suitable way to do it.
TU again for your help!
- Tom, K9BTQ
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