[Elecraft] PA Problem

Mon Nov 24 10:15:01 2003

Hi

Check the PA temperature calibration. Go into the menu and select CAL =
then go to the TPA and set it for the same temperature as the PA heat =
sink in degrees C. If you do not have a way to measure the heatsink just =
set it for the room temperature before the K2/100 has warmed up due to =
transmitting this will usually get is close enough. Also check the =
mounting screws on the KPA100 finals. The screws will need to be =
tightened at least once after a few hours of operation on a new KPA100 =
and this may not have been done.=20

The hum may be coming from your power supply. K2's are sensitive to =
magnetic fields and hum will couple into the radio if the power supply =
is too close to the radio. I have heard of high intensity desk lamps =
causing the same problem. Just keep anything with a power transformer at =
least one foot away from the K2 and do not stack the K2 on top of your =
power supply or anything else that is AC powered and has a power =
transformer.

Don Brown
KD5NDB

  ----- Original Message -----=20
  From: Jim Brown=20
  To: Elecraft List=20
  Sent: Monday, November 24, 2003 1:26 AM
  Subject: [Elecraft] PA Problem

  My K2/100 with KAT100 was about a year old when I bought it six weeks
  ago from a ham who needed the money due to layoff. It looks quite =
clean
  inside, and it's worked fine through a couple of fairly intense
  contests and some intermittent operating, but just started misbehaving
  tonight.=20

  I use the rig with two reasonably trap dipoles that provide a fairly
  good match before tuning on 80, 40, 20, 15, and 10. Any good tuner,
  including the KAT100, gets them close to 1:1. I also have a Ten Tec
  tuner with SWR meter in line with the 80/40 dipole.=20

  Earlier today all was fine. I found myself with some time to study the
  K2 manuals to get more familiar with it, and worked my way through =
some
  of the menus that I hadn't spent time with up to now. I ran through =
the
  PA and ATU menus, but didn't change anything. I did change the t-r
  timing from the default to 0.0 to see what it would sound like.=20

  A few minutes later, I heard some DX on 40 and gave a quick call, and
  the rig sounded sick -- hum in the sidetone and high reflected. After
  checking everything I could think of and powering off and on several
  times, it's still doing the same thing. If I drop the power down to 10
  watts so the PA is off, the K2 works fine barefoot, the KAT100 tunes =
to
  1.2 and then lights to 1.3 or so, and the reflected  reading on the =
SWR
  bridge in the Ten Tec tuner (the Ten Tec tuner is in bypass) doesn't
  move away from 0 with full deflection forward. =20

  I've hooked a 50 ohm dummy load to the K2/100 (i.e., bypassing the
  tuner) and the high reflected problem is still there if the PA is
  running (but not with the K2 barefoot).  I don't see how the PA could
  be hot -- all I've done is quickly hit the key and it immediately =
gives
  me the hot and high reflected messages, and has the buzzy note. I've
  tried powering off, letting it sit to cool, and powered back up. No
  change. I've also tried different antennas and different bands -- 80,
  40, and 20 -- and the problem is the same. =20

  Some other conditions: This rig is sitting in front of a window with a
  bit of a breeze (the window doesn't close very well because I've got
  some temporary coax lines coming through it), and it's turning cold in
  Chicago tonight. As a result, the rig is cool to the touch -- well
  below room temperature when I first observed the problem. The rig has
  not been moved, nothing has changed in the setup or hookup.=20

  I suspect some sort of CAL problem related to the screwing around I =
was
  doing in the menus. Any ideas? =20

  Jim Brown K9YC=20

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