Elecraft K2 Owner's Manual - Manual (Page 157)

5
075 Possible MCU
problem  Measure the voltage on pin 32 of the MCU
(U6, control board). If it is not 5V, check the
5V regulator (052).
 Remove the control board and carefully
inspect the microprocessor. Make sure it is
not installed backwards, has no bent pins, and
is seated firmly in its socket.
 Verify that the MCU oscillator components
all have the correct values and are soldered
properly, with no shorts (X2, C21, C22).
 Listen for the 4-MHz oscillator signal using
another ham-band receiver. If you can't hear
the signal, try putting a 1M resistor across X2
on the control board. Also try rotating C22.
080 IOC Problem  If you saw the message I N FO 0 8 0 , the
I/O controller (IOC, RF-U1) or other auxBus
device did not respond to messages from the
main processor (MCU). Turn power OFF and
back ON; if you hear some relays switching
on power-up, the IOC may be OK, and the
problem is likely to be with the AuxBus
(081)
 If you do not hear any relays switching on
power-up, your IOC (RF-U1) may be
defective. Inspect U1 carefully to see if you
have installed it backwards or if any pins are
bent.
 Pull U1 out, check its pins, then re-install it,
making sure all pins make good contact with
the IC socket. Check the 4-MHz oscillator
(075).
 Remove the bottom cover and verify that all
pins of U1’s socket are soldered, as well as
those of the 6V regulator (RF-U2), and U1’s
4 MHz oscillator (RF-Z5).
 With power ON, check all voltages
associated with U1. You should see 6V at
pins 1 and 20 at all times, even when the IOC
is sleeping (not being accessed by the MCU).
081 AuxBus problem  You may have an option board installed that
is causing a problem with the AuxBus. Try
removing each option board and turning
power off and back on.
 Verify that R64 is installed (RF board, near
U1).
 Check the voltage at pin 1 of the IOC (RF,
U1). If it isn’t approximately 6V, U2 may be
bad (6V regulators).
 Check the voltage at pin 28 of the IOC (RF–
U1). It should be between 5 and 6V. If it is
zero volts, you probably have a short
somewhere on the AuxBus line. Turn power
OFF, then measure pin 28 of U1 to ground. If
it is a short, pull the control board out to see
if the short is on that board.
 If the voltage at pin 28 is between 5V and
6V, try pressing the B AN D + button a
number of times while watching the voltage
carefully (use an oscilloscope if possible).
The voltage should drop below 5V briefly if
the MCU (CTRL-U6) is sending a message
to the IOC. If the voltage does not change at
all, the MCU itself may not be sending
AuxBus messages.
 Check the AuxBus signal at the MCU, pin 40
(CTRL-U6). If you don’t see this voltage
drop below 5V briefly when the band is
changed, the MCU may not be functioning
(075).
090 EEPROM test #1
failed
091 EEPROM test #2
failed  If you saw the message I N FO 0 9 0 or
I N F O 09 1 on the LCD, one of the
EEPROM write tests has failed.
 Check all voltages on the EEPROM (CTRL-
U7).
 Remove the control board and inspect U7 and
surrounding traces. Verify that U7 is properly
soldered.