Elecraft KAT2 - Manual (Page 22)

22
Troubleshooting
If current drain is too high or the ATU menu parameter shows "- - ", verify orientation of all connections between
the ATU module and the K2. You may have a connector shifted by one position, an unsoldered crimp pin, etc. Check
both boards for shorts to ground, solder bridges, and unsoldered connections. Verify that the microcontroller is fully
seated in its socket and is not plugged in backwards. Finally, do the voltage checks listed at the end of this section.
If you can't get a reading of 010 or lower using CALn, or if readings seem way off, examine all components and
connections in the SWR bridge, especially T1's windings (which may be reversed or not making contact). Make sure
you don't have the center conductor and shield exchanged at J7. Check continuity of wires in the control cable (J8).
If the SWR doesn't read 1.0:1 with a 50-Ω load (or other calibrated load), it's probably due to stray reactances (see
Bypassing the Matching Network). C55's setting may also affect SWR accuracy.
If you see an error message in the ATU menu (Exxx, where xxx is between 001 and 199), chances are the EEPROM
(U2) is defective or is installed backwards, or you may have a defective microcontroller.
If tuning is erratic or you see frequent HI-CUR warnings, you may have high RF voltages on the K2 chassis. First,
try reducing power to 1 to 2 watts. If this cures the problem, you may need to improve your ground system, move the
antenna farther away, or use a balun. If reducing power doesn't help, or if tuning is erratic even with a 50-Ω dummy
load, you may have a communication problem between the ATU and K2. Check the value of R5 (470 Ω) and C57 (.001
µF). If these are correct, try removing the SSB adapter's microcontroller (if applicable), then re-test. If this cures the
problem, contact Elecraft. If not, check each of the following components, any of which could cause problems with the
AuxBus line if they were the wrong value: K2CTRL-R6 (470 Ω), K2CTRL-C12 (.001 µF), K2RF-R64 (470 Ω), K2RF-
C140 (.001 µF), SSB-R12 (470 Ω), SSB-C30 (820 pF), NB-R6 (470 Ω), NB-C9 (.001 µF).
If you receive a "distorted audio" signal report when using SSB, you could have any of the RF problems listed
above, or your microphone may be sensitive to RF. Some mics have a DTMF generator IC that can be activated by
stray RF. Try disabling this IC. You may be able to simply disconnect the DC supply voltage to the mic at the Front
Panel mic configuration connector. Also try grounding the mic jack.
If a particular tune-up that you believe should work fails repeatedly, write down the ATU parameters after the
TUNE attempt, including SWR, L, C, NET, Exxx, Txxx, and the ATU firmware revision. Send this data to Elecraft for
analysis. Also try AT U I N IT .
If the tuner is unable to achieve a low SWR on some bands, even with several different antennas, you could have a
single defective relay or component on the L-C board. Start by slowly scrolling through ATU parameters L0 through
L8, C0 through C8, N1, and N2. At each setting you should hear relays switching. If you find one that doesn't, this
may pinpoint a bad relay. You can also check each L and C relay using resistance measurements. For example, when
you select L1, pins 4 and 7 of K1 should be shorted, and with all other Lx settings these pins should be open. When you
select C1, pins 2 and 9 of K9 should be open, and with all other Cx settings, these pins should be shorted. L0 and C0
turn off all L and C relays. If the relays are all working but you suspect an inductor or capacitor, you can test each L
and C by noting their effect on SWR, one at a time. Start on 10 meters. Connect a 50-ohm dummy load to one of the
antenna jacks, select L0, hold TUNE, and note the SWR reading. Then select L1 and hold TUNE again; the SWR
should change by a small amount. L2 should have a larger effect, etc. When the inductance selections cause the SWR
to go off the scale (9.9), switch to a lower band (say 30 meters), go back to L0, then test the remaining inductors.
Similarly, you can test all 8 capacitors, starting on 10 meters with C0, C1, etc. You'll know you have found the bad
component if it has too large or small an effect (or no effect) on SWR, in relation to the others tested.
DC Voltages
All pins of U1 through U4 should measure close to 0 volts (in receive mode), with the following exceptions: U1 pins 1,
11, 20, 32, and 39: 6 V; U1 pin 40, 5.7 V; U2 pins 1, 3, 7, 8: 6 V; U3 IN, supply voltage; U3 OUT, 6 V; U4 pin 8, 6 V.
Tolerance on all measurements is +/- 0.3 V.