Elecraft KX1 Manual - Manual (Page 29)

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E
LECRAFT
LED Tests
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When testing the lamp in the following step, do NOT look
directly at the white LED. It is very bright.
Switch S1 (LAMP) On and verify that D1 lights, then turn it Off.
Switch S2 (POWER) On. If you see or smell smoke, or a
component feels hot to the touch, switch S2 Off and disconnect the
power source immediately. Locate the source of trouble before
proceeding.
You should now see either E10 or 00.0 on the 3-digit LED
display. E10 is an informational code that indicates that the EEPROM
(configuration memory) on the microcontroller has been initialized to
default values. This message will appear only once, and can be cleared
by tapping any of the three pushbutton switches. 00.0 is a portion of
the VFO frequency, which is set to 7100.00 kHz the first time you turn
power on. The display format will be described in a later step.
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After a few seconds, the display turns off automatically if
you haven’t touched the VFO knob or pressed any switches. This
is intended to extend battery life. Moving the VFO knob or operating
one of the pushbutton switches will turn it on again. (The display time-
out is programmable. This will be discussed in the next section.)
Voltage Checks
Connect your DMM’s (-) probe to circuit board ground at the
screw hole next to capacitor C6. Use the (+) probe to check the
following DC voltages:
_ U1, pin 1: 5±0.25 Vdc
_ U3 pin 6: 6±0.25 Vdc
_ D2 anode: Supply voltage.
_ D2 cathode (banded end): supply voltage – 0.3 Vdc (approx).
Leave your DMM’s (-) probe connected to the circuit board
ground, and set your DMM for a 200 to 300 millivolt AC range.
Check the AC voltage at the following pins. A higher voltage than
shown may indicate a problem with one of the voltage regulators as
explained in the note below.
_ D2 anode: < 20 mV AC rms.
_ D2 cathode (banded end): <20 mV AC rms.
_ U1 pin 1: <20 mV AC rms.
_ U3 pin 6: <20 mV AC rms.
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The 2.7 V and 6 V regulators used in the KX1 (U7 and U9,
respectively) are low-dropout types, which may oscillate if their
bypass capacitors are defective or are of the wrong value. If you
see high AC voltage at any of the points indicated above, verify
that electrolytic capacitors C7, C10, and C38 are installed in the
correct orientation and that their leads are properly soldered. If
they are, you may be seeing a false AC voltage indication due to
noise or probe leakage; re-test using a different DMM.