Brian,
You have some problem with the wattmeter in the KPA100 - T4, D16, D17,
R26, R27, U5, U6 or on the VRFDET signal pathway back to the K2 control
board.
You seem to have a somewhat normal voltage variation at U5 pin 7, which
(for the moment) says everything is working through U5, but check the U6
pin 6 output under the same conditions and also check for the same
voltage at K2 control board P4 pin 10.
Since this happened only by removing and re-installing the KPA100, be
suspicious of a solder joint that is not well soldered - those may work
for a while and then when touched can fail.
73,
Don W3FPR
Brian Lloyd wrote:
Our K2 was working perfectly until I opened it up, tightened the power
transistor mounting screws, realigned the receiver, and put it back
together. Now power output no longer follows the power setting. When
set to a power output less than 10W, I hear the bypass relay but I get
the High Cur display (momentarily) and the display then shows a power
output of 0.3W with an SWR of 3.0. Output power as measured with a W1
is 20W. If I advance the power control, as soon as I pass the 10W
point the PA comes on and the power jumps to 150W output. Turning the
power level control fully CCW (0.1W setting) produces 6W of output.
Looking at pin 7 of U5 on the KPA100 I can see good analog voltage
that varies with power. I can see the value of VFWD change when the
range changes (SCALE changes) also. I can also see varying VFWD at pin
2 of U1 so this does not appear to be an analog problem.
FWIW, voltages at pin 2 of U1 for various power outputs are:
6W -- 0.15V
20W -- 0.30V
150W -- 0.29V
At pin 7 of U5 (U5b):
6W -- 0.15V
20W -- 0.30V
150W -- 0.77V
On the t-r menu item I have "8r hold" set.
I do have output on VRFDET but the value only varies from about
0.3V-0.7V so that appears to be working also.
I am planning to fly to Dominica on Friday and operate from there but
I can't take the K2 unless I solve this problem.
Suggestions?
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