I'd appreciate suggestions for finding the cause of somewhat elevated
transmit current on my K2 (serial 02165).
On 7.1 MHz, with all options removed, at full output (about 15 W to a
50 Ohm perfect dummy load) the K2 displays 2.8 A. Other bands are
similar.
This is with actual 13.8 V from the supply. An independent ammeter
in the supply line agrees closely. The supply voltage drops to 13.5
on transmit as measured at the K2 connector. The internal K2 display
shows 13.4 V and 0.22 A on receive, with voltage dropping to 12.7 on
transmit.
I’ve checked toroid values (color and turns count through hole) and
all other components in the bandpass, lowpass, pre-driver, and driver
circuits.
I’ve listed below signal tracing Vrms values below for the
transmitter stages at 5 W output. Compared to the values in the
signal tracing section of my manual, the Xmit mixer and buffer
outputs are low, but output from the bandpass filter is OK. The pre-
driver output is low. The signal voltage on the driver input is very
low. However, the driver output is OK.
The DC voltages on the pre-driver, driver, and PA amp transistors
agree roughly with the manual values.
I don’t know where to go next. Any ideas?
*******************************
Signal tracing values Vrms (expected/actual)
Xmit Mixer Output: .0016/.008
Buffer Output: .200/.065
Band-pass Filter Output: .030/.025
T-R Switch #1 Output: .029/.023
Pre-Driver Otuput: .120/.061
Driver Input: .026/.006
Driver Output: 1.8/1.8
PA Input: .38/.41
RF Detector Input: 2.0/2.0
**********************************
Thanks
Dick, K0KK
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