Well this is a short story from the front trenches.
I have a K2 (serial no. 3792) with KSB2, KAT100 and KNB2 installed and
wanted a bit more power.
Ordered and received the KPA-100 kit without a hitch, and put it
together in about two weeks time. One has to go easy and read the
instructions carefully, and not work when one are tired. But that is
something we all know ;-)
Problem one: There was no way I could get the SWR bridge to minimize.
After some time I found the tech note about the T50-43 and T50-10 cores
and do not mistake one for the other, and see: I have made just that.
Switch the cores, rewind them and bingo I could minimize the SWR bridge.
Problem two: No able to set the idle current. Two evenings later I was
about to throw in the towel and mail Elecraft, when I started to measure
all the voltages around the power transistors. Look and behold Q4 did
not have any 12 V on the collector. Looked at the diagram, was not sure
if there should be a connection, downloaded the PDF file and magnified
the section of the diagram, and yes - there should be connection. After
about 30 minutes of measuring resistance I saw the problem. The PCB
trace leading to the collector of Q4 has been cut and/or scraped off.
Reestablished the connection with a wire - and bingo idle current
worked.
Problem three: PA was oscillating on 40m on antenna (which is about 3:1
SWR) and on dummy load. Blew about 2 fuses before I decided that
something was wrong. Read everything there is to read on internet about
the PA oscillation problem and decided that I was maybe a tad to fast
when I sanded the paint away here and there with sandpaper. My fingers
were telling me a different story, but who listens to them. Took a
drilling machine and a rotating cupper brush and removed the paint
really good. Assembled the PA for the n'th time. Oscillations gone, but
now RF feedback in the speaker on 40m. Nothing else on the other bands.
Shortened the speaker wires from 15 cm to 12 cm (always wondered why
those speaker wires was longer than the other wires) and put a 100 nF
(104) capacitor across the speaker terminals. Now no RF in the speaker
on any bands.
Have since then (Wednesday) had 15 QSO on SSB, RTTY and PSK31 and on
40m, 20m and 17m with this rig. The more I work with it, and the more
problems I have had with the happier I am with the blasted thing.
Happy hunting to all you other happy K1, KX1 and K2 owners out there.
DK1HTX
Henrik Tuxen
_______________________________________________
Elecraft mailing list
Post to:
[hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help:
http://mailman.qth.net/subscribers.htmElecraft web page:
http://www.elecraft.com
Locked
