The swr meter that I was referring to was the one built into my pro III. The
swr only goes high when the amp switches to transmit. If I switch the amp to
standby and transmit through it, the swr is fine.
One thing I forgot to mention in my original post was the fact that I found a
spot where it appears there was an arc over and that was located on the stud of
a 9.1 V 50 watt Zener that is mounted on the back of the case. The feedthrough
insulator and the mica washers had holes blown in them So I ordered a new zener
and mounting kit and replaced it all.....still nothing.
Dave
KB8NNU
________________________________
From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
To: R. David Eagle <kb8nnu@yahoo.com>; "amps@contesting.com"
<amps@contesting.com>
Sent: Sun, February 7, 2010 2:35:16 PM
Subject: RE: [Amps] LK-500NT issue
Unless something went wrong with the SWR meter I would suspect one of two
things happened. One a HV discharge in the RF section produced a high energy
impulse (lots of frequencies) that was detected by the reflected power detector
and thus a very short term high SWR reading. If it had been in the power
supply it would have been filtered out before getting to the SWR meter.
The second is a VHF parasitic or even an out of band HF parasitic
oscillation. Either would be out of the frequency range of your antenna system
and produce a high SWR.
Now back to the opening statement about the SWR meter. If your SWR meter is
an active device that has amplifiers and other electronics in it a transient in
the power supply that somehow propagated to the swr meter and made it go
bonkers is possible.
Maybe a spider wove a web in the wrong place and it is history now.
73
Bill wa4lav
_______________________________________
From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf Of R.
David Eagle [kb8nnu@yahoo.com]
Sent: Sunday, February 07, 2010 12:45 PM
To: amps@contesting.com
Subject: [Amps] LK-500NT issue
Hello all...During the 160 contest last weekend, mr Murphy decided he would
stop by and shut my amp down thus forcing me to run barefoot on 160 during the
contest! While I was calling CQ, I heard a pop noise from my amp and noticed
my SWR went to infinity on the rig and I lost my grid/plate current. I've been
diggin through it this last week and have found absolutely nothing wrong. I am
still getting about 3300 plate voltage so I will assume the HV power supply is
good. The tubes are lit so the filament transformer is working. As far as the
high SWR issue goes, I went through the TR switching and that seems to work
fine. Then I seperated the tuned input from the TR switch and check that with
my antenna analyzer and that seems to be passing RF fine on all bands. I also
checked the shunt resistors and they look fine too.
So does anybody out there in amp land have any suggestions/tips....alcohol...
for this issue?
Thanks,
Dave
kb8nnu
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