Jim,
My usual procedure when tackling a problem of that nature is to first
isolate the problem to one component.
You have already apparently checked out the base K2.
Next, remove the top cover from the base K2 and connect the KPA100 to it
(remove the KPA100 from the EC2 enclosure).
Put the KPA100 upside down on a box or book about 1/2 the height of the
K2 and plug the cables into the K2.
Then test with an external wattmeter and a dummy load connected to the
KPA100 SO-239 antenna jack.
First power the base K2 from the 2.1mm coaxial power jack. Check at 5
watts and at 10 watts - this checks the transmit path through the KPA100
in QRP mode. Use an external wattmeter and a dummy load. Does the
external wattmeter agree roughly with the K2 display indication and the
power knob setting.
If you have a much higher actual power level on the external wattmeter,
the KPA100 wattmeter diodes D16 and D17 are the first suspects - replace
them.
If all is well so far, remove the 2.1mm power plug and power the
assembly with the APP connector on the KPA100. Make the same test.
After that, check the bias on the KPA100 for a 400ma rise in current
with the K2 set to CW and in CW TEST mode. Hold the mode button until
TEST appears in the LCD, and the CW icon will blink.
Do a tune and check that the current rise from receive to TUNE is 400ma.
Then set the power to 50 watts and do a TUNE. Read the actual power on
the external wattmeter. With a TUNE, it should be about 20 watts.
If it is greater, you have a problem with the KPA100 wattmeter - likely
diodes D16 and D17 have been damaged and need to be replaced.
More troubleshooting is possible, but that is a good starting point.
If all goes well with those tests, then I can tell you how to check the
KAT100 alone (without the KPA100).
73,
Don W3FPR
On 2/3/2019 10:13 PM, Jim KO5V wrote:
I tried to tune the KPA/KAT100, and the SWR went to red. I quickly exited
'tune', checked all of the connections, and the antenna, and tried again. Same
result, except before I could take it out of tune (it was tuning maybe 2-3
seconds), all of the KPA/KAT100 lights went out. The K2 was fine. I took the
amp off of the EC2 and installed it directly on the K2. When I powered on the
the K2, using its low-current supply, the K2 came up normal, and didn't
recognize the amp. The base K2 seems OK, and transmitted into my dummy load,
and could hear the NGEN. When I powered it through the KPA's high-current
supply, the K2 was dead. The base K2 again came back to life when I removed the
KAT's power, and went back to the base K2's supply.
I measured the 12V supply when plugged into the KAT100, and I get between 1V
and 2V - the PS must be protecting itself - it looks like there's a short...
Earlier today, I had been trying to get my computer to talk to the K2 through a logging
program. After I built the rig, I tested my cables and the KIO2 by successfully controlling
the K2 with 'K2 Remote', so it was working. Today, the logging software would poll the K2, and
get no response. 'K2 Remote" couldn't see the rig either. The DB9 connector that connects
to the KIO2 has the cables to the KPA/KAT and serial cable, and I made sure the computer's
connector was wired correctly for interfacing a "normal" serial cable to the KIO2.
It all worked.
I looked at the KPA schematic, and thought a diode, or something in the current sensing
circuit might have failed. I removed Q5, and it tests just like my new spare. I lifted
one side of D10, and it seems to test OK, but when I did the same to D9, it looked weird
- but I don't really understand that device; In "diode" mode, I get .150V in
one direction, open in the other. When I test it in resistance, I eventually measure
80-90ohms in one direction (it takes a moment to settle), but it's open in the other. It
might be OK? I hope I didn't kill U7.
I performed the resistance tests in the KPA manual, and they are nominal. Q1
and Q2 test OK, and I think Q3 and Q4 are OK. Q3 tests differently than Q4, but
looking at the schematic, I think what I see makes sense.
It also occurred to me that when I was trying to get the logging program to
work, I might have caused a failure in my cables while I was hooking and
unhooking the serial connection. That might have caused a communication problem
that made the amp go a bit nuts.
Sorry for the long message. ANY suggestions will be greatly appreciated!
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