Hi guys,
I am helping a friend trouble shoot a K1 that he just finished putting
together. This is a 2 band 40/20 meter K1. The 40 meter band is working
perfect with a full 7 watts output into a 50 ohm dummy load. The power
output can be adjusted up and down while in transmit on 40 meters. The 20
meter band has a problem. It will only put out 3.5 watts and once the power
is set all the way up you can not adjust it back down while in transmit. The
power can be adjusted up and down while in transmit on 40 meters. I have
used an RF probe on the filter board and here are the voltages I am getting:
RF Filter Board voltages using a RF probe 20Mtrs 40Mtrs
P1-4 Premix oscillator signal 200-500mVpp 192mV 561mV
P1-6 Premix signal output signal 55mV
800mV
P2-1 TX Buffer output 1-3Vpp 740mV
880mV
P2-8 Filter board TX output to driver 1-3Vpp 624mV 1.7V
P3-1 PA output up to 40-55Vpp 14V
19.8V
P3-8 Output from lowpass filter 40-55Vpp 13.59V
18.78V
The voltages are shown as to what should be expected using an O scope which
I do not have. The RF probe readings will be 35% or so less than what an O
scope will show according to Gary. I have verified the toroids and actually
rewound them all and made sure the leads were properly tinned and
reinstalled them. Where do I look for the problem? I am also guessing the
problem is on the Filter board and not the RF board due to the fact the 40
meter portion is working as advertised. The 20 meter crystal on the filter
board was also replaced due to being suspect. I am guessing a bad capacitor?
Any help would be appreciated.
Glenn WA7SPY
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