[Amps] LK-500NT issue

[R. David Eagle]

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 at uky.edu>
To: R. David Eagle <kb8nnu at yahoo.com>; "amps at contesting.com" <amps at 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 at contesting.com [amps-bounces at contesting.com] On Behalf Of R. David Eagle [kb8nnu at yahoo.com]
Sent: Sunday, February 07, 2010 12:45 PM
To: amps at 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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