Aloha, a few comments about the AT4K;
I have had mine for several months now, well
nearly a year, I guess.
> I went up to Piqua, Ohio yesterday and dropped in
>on Palstar.
Have you gone to their web site? Go to:
http://www.palstarinc.com/palmain.htm
Paul gives good support, also.
> I really liked their high-power tuner - very impressive!
>The tuner even uses a Jennings vacuum relay to switch
>in extra capacitance........
??, Must be a new addition; my unit switches the extra
output C via a second big wafer rotary switch. The vacuum
relay would require the DC power to the tuner be ON when
switched in. I no longer use the DC power to the tuner (see
below), have not so far needed the fan to cool the inductor.
>The swr bridge is very well done.
All of these components have been removed from my unit.
I had too much trouble with this circuitry directly on the
back of the input RF connector (inside the "can" in the
lower left corner of the top view of the tuner at the web
site). I had trouble with arcing around the small toroid
power pick-off in the Palstar vswr/ fwd,refl setup. Also
completely burned up one of the detector diodes, and
rather badly burned the small PC card on which the diodes
are mounted!
The first four turns on my power "pick-off" sensing toroid
are obviously "burned". This is on the outside of the toroid,
not inside where the toroid surrounds the "bolt" used
soldered to the center conductor of the input RF
connector. The insulation on the windings about the
toroid appears to be pretty thin, maybe not
heavy enough?? The next five turns, though not appearing
singed, have developed small green splotches!? Each
splotch getting smaller on the following winding turn.
(Paul: If you are reading this, I could send all of
these parts back to you for your analysis, should you
care to have a look at them.)
Cause may be that it is difficult to keep the toroid
centered about the pass through "bolt". Mine was down
against the bolt, so the insulated wire was resting
directly on the RF current carrying "bolt". A couple of
washers held tightly by nuts against the windings about
the toroid are evidently supposed to keep this assembly
centered and the windings up and off the RF conductor.
Anyway, I removed all of this vswr, forward, reflected
power pick off PC card circuitry, the "bolt" and toroid, and
the can which surrounded it all. Soldered the heavy insulated
wire from the large and impressive appearing wafer
directly to the input RF connector center pin.
The AT4K works outstandingly well now. No more
arcs, etc. Sent email to Paul about all of this, no
response about this vswr componentry; though he
did respond with info about the construction of their
very nice roller. I thought it was actually built by
Henry Radio; not so, but patterned after the
Henry design, per Paul. And he told me he does purchase
a couple roller parts from Henry -- as Henry has
the tooling that is required to machine the notches in
the mycalex material that is used for the coil separators.
Anyway, thought you might find my experience interesting;
Probably my troubles with the toroid circuitry were
due to odd ball problems with the rest of my rig setup,
but I no longer have to worry about those parts
in the tuner -- they are out of there, hi! I could just
as easily have had intermittent in my antenna system which
reflected back odd ball Z's, shorts or opens which could
have zapped the windings on Paul' toroid power
flow sensing bridge set up. Just be careful when tuning
up at QRO. Get most of it done at low power, or use
an antenna analyzer to set up the tuner; I am now using
the MFJ-259 for just that purpose. And I keep a Bird 43
in my set up, with a 100 watt slug in the reverse power
sense position. With this, I can quickly tweak out any
reflected power reading should I QSY a bit, thus changing
the Z seen by the tuner from the antenna system. I use
the very nice RF Apps VFD bargraph for amp tune up
into a dummy load, so no longer need the peak power
reading bargraph display in the AT4K (which of course
no longer functions in my unit, nor does the twin needle
metering of forward/reflected power, hi).
Were I setting out with a brand new AT4K, I would open
it up and have a look inside the vswr bridge "can". Check
to be sure that during shipping, the unit was not jarred
sufficiently to knock the toroid pick off transformer
off center and down against the RF pass through
conductor. Perhaps that is what happened to my
unit during shipping out here, and why it these
components failed. I have not heard of any other
user of the Palstar tuner having this sort of problem.
73, Jim, KH7M
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