I had (have) a problem, and my intent in this post is to add an article to the archive so that if some other fool makes the same mistake it may save them some time in the troubleshooting process. Description of the problem: The KPA100 and KAT100 are remote in an EC2. After working on the K2, I buttoned up the case, connected my control cable, and on start the KPA100 failed. Most of the time the PA was not recognized, but once in a great while it would be recognized briefly. When that happened no PA functions were available in the secondary menu, and after reducing power to below 11 watts the PA ceased to be recognized, nor did K1 switch. However, the KAT100 was operational. Troubleshooting: Performing the resistance measurments at U1 indicated a short at pin 1, the 5v line. Assuming U3 had failed I removed it from the circuit. The short remained after the removal of U3. C25 tested fine as did C89. That left two suspects, U4 the MAX1406 and U6 the EL5146C. OK, a 50/50 shot so I removed the MAX1406 and the short still remained at pin 1 of U1. After pulling the EL5146CN the short disappeared. Lacking those chips I installed a new 78L05, and suddenly the KPA100 was recognized by the K2, and going from QRP to QRO K1 switched as expected, and passing through the bands all the low pass relays were operational. Now I wait for the mailman to bring me replacement MAX1406 and EL5146 chips. The cause: When U6 failed it shorted the 5v line disabling the MCU, it wasn't quite a dead short, showing about 13 ohms of resistance. Thus once in a blue moon it would be recognized on power up. So what happened that could cause this? In my haste to button up the K2 which has a KIO2 and KAT2 installed in the lid I didn't get the KIO2 cable on P4 on the control board aligned right. As a result of shifting the pins one row up I applied 12 volts to the RFDET line in the KPA100 causing failure of U6. It isn't used in the KAT100 so it was spared. The moral: Key the plug on the control cable of the KIO2 so you might avoid the pain and shame I experienced. Regards, Joe N9JR _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft
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