Elecraft K2 Owner's Manual - Manual (Page 155)

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 Make sure the bottom cover is installed when
doing CAL FIL and CAL PLL . Also, if
you calibrate at room temperature but operate
the radio at much lower or higher
temperatures, calibration will be worse.
 Re-do CAL FIL after calibrating the
4.000–MHz oscillator
 Re-do CAL PLL after calibrating the
4.000-MHz oscillator
 Use CAL FCTR with probe on TP1 and
tune very slowly through about 10 kHz of
VFO range; if you see any sudden jumps of >
50 Hz over this range even after doing CAL
PLL, your 12.096-MHz oscillator crystal may
be defective (RF, X1).
030 VFO frequency
jumps or drifts, or
operating frequency
appears to be entirely
incorrect  You must align both the VCO and BFO using
the CAL PLL and C AL F I L before
operating the K2; otherwise the VFO cannot
be tuned properly and the synthesizer may
not be locked (see Operation as well as RF
board Alignment and Test, Part II)
 Make sure the supply voltage is above 8.5V
at all times or the 8V regulator may not
function correctly.
 If you used solder with water-soluble flux,
you may have conductive paths all over the
PC boards. These can cause numerous
problems with the VFO, BFO, and logic
circuits (anything high impedance). Try
cleaning the entire board with hot water and a
Q-tip, or follow solder manufacturer’s
recommendations (except immersion).
 If you used CAL FIL to change the BFO
settings, make sure you placed the BFO on
the correct side of the zero-pitch value for
each operating mode (see Operation, Filter
Settings)
 If you tune beyond the lock range of the
VCO, the frequency will stop changing and
may “hunt” near the end of this range. If you
are in a range that the VCO should be
capable of tuning, re-check VCO alignment
(see RF board Alignment and Test, Part II)
 If the displayed frequency is “garbage,” see
Resetting the Configuration to Defaults in
Advanced Operating Features.
Control Circuits (050-099)
Problem Troubleshooting Steps
050 Regulated
voltage(s) incorrect  Remove all option boards, since any one of
them might be causing a short on a regulated
supply line
 Make sure that the DC input voltage at J3 is
> 8.5 (the minimum voltage needed by the
voltage regulators)
 If +5V is too low (< 4.5V) go to 052
 If +8V is too low (< 7.5V) go to 053

051 General problem
with control circuits
(switches, knobs,
display, bargraph, T-R
switching)
 Check all DC voltages using the voltage
tables (later in this section). Start with the
control board.
 If the problem involves the front panel,
measure those voltages next. If the problem
is with T-R switching, check the RF board
voltages next. You may have RP1 or RP2 on
the front panel board installed backwards.
052 +5V too low
(< 4.75V)  Remove the front panel to see if it is was
pulling the 5V line low. If not, the problem is
likely to be on the control board.
 Pull the control board out and inspect the
entire 5V line looking for heat-damaged
components or shorts. The schematic can be
used to identify components on the 5V line.
 Remove the microprocessor to see if it is
loading the 5V line down.
 Unsolder the output pin of the 5V regulator
and bend it up slightly to break contact with
the PC board. If the voltage is still too low
measured at the pin, replace the regulator.
