Hi experienced ones,
Not sure if the AMP reflector is the place for
my questions, but don't know where else I
could find someone who might have the experience
to answer, hi.
I had a call from the Service Center for Yaesu
in Cerritos. I sent my FT-1000D to them just Friday;
talk about instant service! The radio was delivered
from Hawaii to them by Fed Ex Monday morning;
the tech called Monday 4:30 pm PST.
Anyway, he reports that for the second time, happened
also last Summer, that I have managed to get enough
RF into the rcvr front end to blow something called
an RF Surge Protector. This is Yaesu P/N DSA-301LA;
in August the invoice cost for this part was $2.52. Of
course, it cost $90 each way from Kauai to Cerritos
via Fed Ex, plus $75 labor to Yaesu!! Much the same
is now recurring.
I cannot find anything about an RF Surge Protector in the
Yaesu manual for the FT-1000, nor in any of the diagrams
in the back.
Symptom I had was that the transmitter would not transmit,
but the rcv section seemed just fine to me. Most power I
could get out was about 12 watts on any band, and
the vswr indicated very high, even with the radio terminated
into a good dummy load. Certainly the high vswr is why the
output power was so far cut back.
Yaesu tech also asked if my QTH had suffered a direct/
nearby lightening strike -- I assured him not.
But something is wrong, as I am sure this same thing
occurred a few years ago to my 950SDX, some little
coil had opened in it, and would not xmit.
I use an Alpha-Delta-4 switch with which I select between
my Ten Tecs and Yaesu transceivers, and previously the
950SDX .
So, if I am using the Ten Tec as the driver for the Henry
amp, might there be some way for RF to get into the
Yaesu, even when it is not turned ON, and has the
A-D switch between it and the Ten Tec drive line.
One note: I have not yet, but am today, running braid
from my station ground system to that Alpha-Delta
switch, was pointed out to me that that might be the
problem. But, the A-D switches short the coax
center conductor to the shield/ground when the
position is not selected, right? So my center
conductor from the Yaesu should have, at least
been shorted to all the coax outer shields attached
to the switch.
However, I can't see how 80 or 90 watts from the Ten
Tec, attenuated by whatever the isolation of the A-D
coax switch might be, would be enough to blow the
diodes protecting the Yaesu front end. Nor do I see
how the output power of the Henry could get in there
either.
A strange situation. I can easily take the switch out,
and just "hard wire" to which ever transceiver I would
be using, but that does not seem necessary to me.
It really seems to me that the Yaesu failed one afternoon
while I was using it along with the Henry amplifier. But
again, I cannot imagine how RF could get into the Yaesu
and damage it when it is acting as the driver for the amp.
I suppose the Yaesu might quit driving and open the rcvr
while the Henry is still outputting energy? But how would
that get back around into the input line to the Henry which
is coming from the Yaesu driver?? Also, this "accident"
may have happened while I was fiddling with the rig
Processor and Drive/ALC knobs; could something
backfire while driving the linear and adjusting these
to blow out the Surge Protector?
I guess I don't understand the Yaesu circuit anyway, as
if the diodes are blown in series with the output FETs,
how could they get blown by something coming in the
rcv line without hurting the rcvr operation, which seems
fine to me??
Anyway, wondered if this was something anyone else
has experienced using a linear? This could even
have occurred while I was tuning up into the Bird load,
I suppose. As I understand, you are to tune up using
pretty high power, then back the drive back such that
you actually will output only 1500 watts peak on SSB;
this method is supposed to get you max linearity and
lowest IMD products. So I have been tuning up at
around 3kW into the Bird load. And separately,
using the MFJ-250B gadget, to set up the
antenna/antenna tuner to provide the 50 ohm load to the
linear; certainly seems to work FB for me. Except maybe
has caused my Yaesu problem??
Any ideas, or maybe some electrical surge did get
on my transmission line somehow....static, who knows!
Does anyone sell an external "RF Surge Protector" which
would go out, and I could fix/replace without another
$257.52 cost incident? Must be some gadget like that
to protect these expensive rigs.
73, Jim, KH7M
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