Posted by
Jim KO5V on
Feb 04, 2019; 3:13am
URL: http://elecraft.85.s1.nabble.com/K2-I-killed-my-KPA100-tp7648715.html
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!
73, Jim KO5V
(and I was recently bragging that it was all working so well)
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