Interesting thought, but there is no indication of any impedance change
external to the amplifier. Other bands via the same ATU are normal.
The ATU matches both 10 and 12 to 1:1 and the Omni-V will happily run flat
out. Turn on the Herc and its anybody's guess what will happen.
I had exactly the same symptoms when I used my 50 ohm oil filled Cantenna as
load. Right now the dummy load is not cabled to the main antenna switch, but
I can soon re-connect it. I can also bypass the ATU, although that seems to
make no difference.
Tricky ....................... but I still think it is most likely inside the
Herc circuitry. Unless someone knows better, or you are right and there is
something amazing going on. Note that the actual antenna used seems
irrelevant and the SWR shown on the ATU and on the external bridge appear
73 John G3JAG
On Thursday 27 July 2006 21:24, Donald Watters wrote:
> John -
> Are you absolutely positive that the load inpedance on 10/12M is an actual
> Ohms? If the Z is low then excessive current will be drawn and the PS will
> Just a point and a possibility, OC.
> Don, VE1BN
> ----- Original Message -----
> From: "JohnCrux" <firstname.lastname@example.org>
> To: <email@example.com>
> Sent: Thursday, July 27, 2006 5:14 PM
> Subject: [TenTec] Hercules II problem
> > 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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