Elecraft K1 - Manual (Page 86)

4
Transmitter and Keyer (80-99)
Problem Troubleshooting Steps
80 General
Transmitter problem If power output is too low, go to 86
If power output slowly increases during key-
down, go to 88
If current drain on transmit is too high for the
given power level, go to 92
If the transmitter output power seems to be
unstable go to 88
If the transmitter stops transmitting by itself
go to 90
If the keyer isn’t working properly, go to 95
Try signal tracing
86 Power output is
low or zero Check power output when using a 50Ω
dummy load; if the output is correct on a
dummy load but not when using an antenna,
your antenna is probably not matched
Check all component values in the RF
detector; you may have two resistors
swapped (R36, R37) or the wrong detector
diode (D15, should be 1N5711)
You may have a short in the LPF or BPF;
also check relays (25)
Examine T3 and T4; these must be wound as
indicated in part II of the RF board assembly
Look for toroid leads that are not completely
stripped or are soldered poorly
Check all DC voltages in the transmitter (RF
board, Q5/Q6/Q7, U8, U9)
If drive is lacking, R35 (RF board, TX
attenuator) can be made larger, at the expense
of power-setting resolution.
Make an RF probe and signal-trace through
the transmitter to find where signal is lost
(see probe and procedure later in this section)
Check for any components getting hot
Check for RF-Q7's tab shorted to the right
side panel (ground)
88 Power output
fluctuates If you stay in key-down (TUNE) mode for
several seconds, it is normal to see some
increase in power; this is due heating of the
final amplifier transistor.
If power goes up and down significantly
during normal keying, you may have a
poorly-matched antenna OR you may have
power set too high for your battery or power
supply to handle; try reducing power
Make sure none of the diodes in the T-R
switch circuits are in backwards
If the transmitter is unstable (oscillating)
even when connected to a 50-Ω load, you
may have an incorrect component value or a
toroid-winding error (86)
90 Output power
drops to zero suddenly If you have transmit power set too high for
your battery or power supply, the supply
voltage may drop so low on transmit that it
resets the MCU (FP-U1) or the I/O controller
(FIL-U1). Reduce power.
92 Current drain too
high on transmit You may have power set higher than the final
amplifier can achieve for a given load or
power supply voltage, resulting in overdrive
of transmitter stages. Reduce power to see if
normal current drain is restored.
Damaged PA transistors or other components
could cause inefficiency in any stage of the
transmitter. Check all DC voltages and
components; signal trace if necessarily (86)
95 Keyer Problem If the keyer is generally erratic when
transmitting and seems to get worse as power
is increased, you probably have RF leaking
into the keyline. Try bypassing your key with
.001 µF capacitors; also try 100 µH RF
chokes in series with the paddle connections.
Seek a better antenna match
Improve your ground system (if you have RF
problems, add two or more radials cut to 1/4-
wavelength at the affected frequency)