Desperation time.
I repaired my 9420 PSU and reset the four 25 amp rails at exactly14 v
under
load. I repaired and re-aligned the Omni-V.
Then I re-assembled the entire station, including the auto-atu. All
inter-connecting/control cables are original TT. My added 120 amp
commercial
ground bus wire connections linking everything are rock solid as are the
coax
connections.
For a few days there was no problem getting 500 watts from the Hercules II
on
any band 10-80m (not tested 160; no antenna at present.)
That held good for a week or so. Then a very old problem came back to
haunt
me. The Herc trips out ("fault") at around 150 watts out on 10m and at
around
250 watts out on 12m. Switch off and back on, and all other bands work as
before. The SWR remains as before on all meters ( Herc, ATU and external
SWR/power bridge. It is 1:1 or very close.
But it does not always trip. Today after having it trip at 150 watts on
10m, a
little while later it ran perfectly OK on 12m at 400 watts out. I have
also
had 10m return to normal output from time to time.
It is unpredictable, except that if it trips on 10 then will probably do
so on
12m.
OK; I already swapped the 10/12m low pass filter in the Herc. The Omni-V
is
working fine on all bands including 10/12m and gives normal output.
My best guess is that this is maybe a mechanical problem with one or more
bandswitch relays. The front panel bandswitch is normally set to "auto",
but
even if I manually select 10/12m, it makes no difference, so the switch is
probably OK.
The Herc manual indicates that it is not just a matter of the relays
switching
in that LPF for 10/12m. Other relay contacts appear to be used to disable
(short ?) other band filters, perhaps to avoid stray resonances in the
unused
circuits.
Anyone seen this problem (including my friends at TT service, please !)
and is
there a solution ? If only I could pop the covers off the relays to check
the
contacts ..... Surely someone has seen this ????
Yes, I know it is no longer made, but the Herc is a super amplifier and I
have
made many QSOs with it. Just need to get 10/12m back in service reliably.
73 John G3JAG
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