Posted by
Jim KO5V on
Feb 06, 2019; 9:59pm
URL: http://elecraft.85.s1.nabble.com/K2-I-killed-my-KPA100-tp7648715p7648760.html
Hi Don,
I got the following results:
1. Base K2 seems to be OK.
2. The KPA100 is upside down next to the K2, and everything is powered through the K2 and its power supply. Using the LP-100 and 50ohm dummy load, the 5W and 10W measurements through the KPA100 check out nominally.
3. When I apply power through the KPA100's power port, and using its power supply, the K2 and KPA100 are dead. The power supply measures about 1.8V when plugged into the KPA100, but ~13.5V with no load.
4. As I mentioned below, I previously checked D9 and D10 and Q5. D10 and Q5 were OK, but I didn't really understand what I saw when I checked D9. From my first post:
"I lifted one side of D10, and it seems to test OK, but when I did the same to D9, it looked weird - 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?"
Next?
Thanks. 73,
Jim KO5V
-----Original Message-----
>From: Don Wilhelm <
[hidden email]>
>Sent: Feb 3, 2019 8:50 PM
>To: Jim KO5V <
[hidden email]>, Elecraft List <
[hidden email]>
>Subject: Re: [Elecraft] K2: I killed my KPA100
>
>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:
>> 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.
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