Don,
I'm trying to replace D16 and D17 in the KPA100 but I'm having trouble
removing the heat sink so that I can get at them (it looks to me as if I
have to remove the heat sink to get at the bottom of the PC board to
unsolder them).
I have removed the three black pan head screws that attach the
John
If the board has not been removed a few times, it often sticks on the
screw threads - I suspect that is the problem. I usually use a
flat-blade screwdriver between the heatsink and the board to carefully
nudge it up. Watch where the screwdriver is going (peer between the
board and
I would like to put my K2/100 back to a basic K2 as part of debugging some
problems I've had around power and RFI distortion. I have the K2, KPA100,
KSB2, and KNB2 installed. My plan is to only remove the KPA100 at first to
see if that corrects the problems I've been having.
As I understand it,
Jon,
You have the KPA100 removal steps correct, but I suggest that you do not
do that yet.
Instead do a quick test - remove the APP connector from the KPA100 and
power the K2 from the coaxial power jack.
Then set the power at 5 watts and measure the power output with your
external wattmeter
Don,
Thanks as always for your reply.
But you don't seriously believe that my problems with electronic equipment
could be THAT simple, do you?? After all, I'm the guy whose dog ate one of
the ICs while I was building the K2 (no joke).
I ran 5 watts and 2.5 watts, and ran each test five times
John,
I believe after you replace diodes D16 and D17 in the KPA100 (both are
1N5711), you will find the problems go away. What appears to be
happening is that they are not fully open nor shorted, but are at some
state in between, so you do get some control, but it is just not right.
Replace
OK, thanks Don.
I'll order the diodes (local Radio Shack doesn't carry them anymore). In
the meantime, I think I will remove the KPA100 anyway to see what impact
that has on the RFI problem.
Do you think that this is also impacting the SWR reading that I'm getting in
tune? Both the MFJ and the
Of course it is Jon, one diode rectifies the forward power and the
other the reverse power.
BUT - I hope you do not have the KAT100 in line between the KPA100 and
the external wattmeter when you make that evaluation - if it is, you
should first put it in CAL mode using the K2 menu.
73,
Don
Duh! Sorry, I wasn't thinking when I asked that.
The KAT100 is out of the circuit completely. All my testing has been with
the MFJ-941E.
I just removed the KPA100 and tested. My power levels are as commanded
(usually a little better, but not double) AND my PSK31 signal looks like a
Jon,
Your 1/3 rule is right for continuous duty data modes like RTTY, but I
understand (and have not tried to figure out the details for myself)
that plain PSK31 does not come up to a full duty cycle - something about
the coding, so you might go up to 1/2 the normal rated power - 6 or 7
A couple of other points to consider:
1. I find that my K3's finals get hotter in PSK31 at 50% power than they
do in RTTY at 100% power, but that's very likely due to the fact that my
RTTY QSOs are in contests, with very short transmissions, whereas my
ragchew-style transmissions in PSK31 last
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