Mike,
The current draw now looks to be in line with the power output, but your
output drops off with increasing frequency.
First measure the voltage at the base of Q7 and Q8 during transmit. If
it is not in the range of 0.60 to 0.64 volts, replace Q11 and Q13.
Since you are measuring the receive signal path, and have verified that
the internal K2 signals are OK, you apparently have a problem in the T/R
switch or the Low Pass Filter. I suspect the T/R switch first.
Make certain all the RFCs in the T/R switch are not open - including the
RFC3 toroid, and check the orientation of diodes D1 through D5.
In receive, do you have 8 volts at the anode of D4? The cathodes of D3
and D4 should be at least 0.4 volts (preferably 0.6 volts lower than the
anodes.
Is RFC3 wound on a gray ferrite core? If wound on a black core, that is
your problem.
Once you do those checks, skip to the Transmit Mixer, Buffer, Bandpass
Filter, T/R Switch tests during transmit (or TUNE) on page 14 of the
manual Appendix E. At which point in the sequence does the RF voltage
drop significantly lower than the Expected value - ignore any RF
voltages which are higher than the Expected value (except for the T-R
Switch #1 which should be lower than Expected).
73,
Don W3FPR
On 10/3/2019 8:45 PM, K5MMH wrote:
After a several month hiatus from radio, have discovered my K2/100 (S/N 3010)
has some issues with transmit power on some bands and a receive issue on 10m
and 12m. I am the builder of this K2.
10m = 1.02 w @ 1.38 amps
12m = 1.81 w @ 1.46 amps
15m = 3.90 w @ 1.52 amps
17m = 3.70 w @ 1.52 amps
20m = 6.40 w @ 1.84 amps
30m = 8.30 w @ 2.26 amps
40m = 10.90 w @ 2.10 amps
80m = 7.10 w @ 2.42 amps
Then proceeded to Page 10 of K2 Appendix E and performed receiver signal
tracing in attempt to find receive issue on 10m and 12m. Here are the
readings using RF probe and external signal generator, comparing 30m and
12m:
PLL section Page 10, # 2 30m = .765 12m = .721
Page 10, # 3 30m = .310 12m = .341
Page 10, # 4 30m = .642 12m = .632
BFO section Page 11, # 1 30m = .448 12m = .445
Page 11, # 3 30m = .032 12m = .035
LPF section Page 11, # 9 30m = .132 12m = .054 >>>>>>> low
Page 11, # 10 30m = .126 12m = .036 >>>>>>> low
Page 11, # 11 30m = .042 12m = .021 >>>>>>> low
Page 11, # 12 30m = .039 12m = .020 >>>>>>> low
So, I am seeking assistance on correcting the low power output on the high
bands and the receive issue on 10m and 12m.
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