To trouble shoot the continuity of the AUX bus between the main processor (U6 on the control
board) and the I/O controller, IOC, (U1 on the RF board.), do the following:
1. Measure the resistance between pin 28 of U1 on the RF board and pin 40 of U6 on the
control board. It should measure between 900 and 1000 ohms. If it reads open, check R6 on the
Control board (near U6) and R64 on the RF board (near U1). Both should be 470 ohm resistors.
Also check to make sure these parts are soldered in and that the pins on both micro- controllers
are soldered.
2. Make sure the AUX bus is NOT shorted to ground. Check both sides of R6 on the Control
board and R64 on the RF board.
As a final step, check to make sure the I/O controller (U1,RF) is programmed. There is a small
chance that this part left the factory in the unprogrammed state. To do this, measure the
voltage on pin 28 of U1 with the K2 power on. The following measurements can vary +/- 0.2v.
~5.5V indicates U1 is programmed OK and the AUX bus is OK.
~6V indicates U1 is programmed OK but the AUX Bus is open.
~5V indicates U1 is NOT programmed, but the AUX bus is OK.
~0V indicates U1 is NOT programmed and the AUX Bus is open.
If you determine U1 is not programmed, please contact us immediately at radios@elecraft.com
and request a new U1. Let us know you followed this trouble shooting procedure.
Also, you can follow the troubleshooting chart for INFO 80 on page 4 of the trouble shooting
guide, Appendix E, in the K2 manual.
IMPORTANT NOTE (After fixing your INFO 80 problem):
The first time the K2 is powered up it initializes its nonvolatile memory and displays an INFO
201 message. If you receive an INFO 80 message (indicating the main processor is not talking to
the I/O controller) when doing the first building test on your K2, this step is skipped.
After you fix the cause of the INFO 80 you will also need to force a hard reset to initialize the
K2's nonvolatile memory.
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