Ed,
Lack of power control with the KPA100 installed normally points to a
failure of the KPA100 wattmeter circuit.
Start with replacing the 1N5711 diodes D16 and D17. It could also be
that U5 and/or U6 are not performing properly.
If your KPA100 was working at one time and there is *any* possibility
that you encountered a lightning surge, then D16 and D17 are the most
likely suspects.
If it has not worked before, look at the soldering (especially U5 and
U6, check all 6 leads of T4 for proper orientation and tinning - make
certain the red wire goes through the center of T4 and the bare wire
from the SO239 jack goes to hole #6. There are a few other
possibilities, but those should get you started on the right track.
The bottom line is that the base K2 is not getting a proper indication
of power output from the KPA100 wattmeter and the base K2 develops full
output because it thinks the power output is low - in other words, you
do not have power control. When you totally remove the amplifier and
the power control is restored to normal, that indicates that the K2
power control is functioning and the problem is in the KPA100 wattmeter.
73,
Don W3FPR
eKotz wrote:
When the KPA100 is not installed, my K2/QRP operates normally.
However, with KPA100 installed I have no incremental power control and
no lit LEDs on the K2 S/RF meter.
The SWR is indicated to be 1:1 into an OHR RFL 100 Dummy Load. "HiCur"
does flash on momentarily after switching to the 80 & 40 meter bands.
I am using my straight key to key the K2... not TUNE.
First test on 40Mtr band:
Both Hi Current and Lo Current Power Supplies on:
Requested power = .1 to 10w, power to dummy load = 20w
Requested power = 11 to 110w, power to load = 110w
With only Lo Current Power Supply on:
Requested power = .1 to 15w, power to load = 10w
I cycled DC power off/on:
Requested power = .1, power to load = .3w
Requested power = 10, power to load = 10
I backed off requested power:
Requested power = .1, power to load = 10w
I turned Hi Current Power Supply on:
And raised requested power:
Requested power = 20w, power to load = 110w
Then backed off again:
Requested power = 9.5w, power to load = 10w
Band Initial Power readings after I
raised
(Mtr) Power requested pwr past about 1w.
(With Hi and Lo Current Power Supplies on:)
160-15 0 20, 110
12, 10 0 3, 25
(With only the Lo Current Power Supply on:)
160-15 0 10, 10
12, 10 0 3, 3
(The lower power readings read when =< 10W requested, the higher power
readings read when > 10W requested and the Initial Power is what I
read just after switching bands)
"HiCur" does flash on momentarily after switching bands.
There are no INFO ### messages.
My equipment for this test: OHR WM-2 (QRP) and Heathkit HM-2140 (QRO)
watt meters and OHR RFL 100 and Heathkit Cantenna dummy loads.
The testing steps during the KPA100 build checked out properly. I have
double checked the solder joints and reworked those that I thought might
have been questionable with no change in the (mis)behavior. I don't
know if these findings are of any help to you... I would be glad to
supply whatever readings as I may be able.
Troubleshooting suggestions appreciated!
Thanks,
Ed - AD7GR
K2 #6050
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