[Elecraft] K3 Very Low TX Power below 14 MHz

[Andrew UK]

Hi Does anyone have any idea what has happened:Scenario:TX cal will not work
as there is zero watts on 1.9 MHzK3 Died on TX while tuning up on 1942KHz on
an AL-811H Ameritron Amplifier, which had word fine previously.The LPA
transistors, bias was upset, and Q2 not getting as hot as the others,
however, all 3 replaced and bias set: it made not difference:I get the
following:I performed a factory reset and recalibrated from scratch and
reloaded all the firmwareAutomatic Transmitter gain will not run as there is
zero watts on 1.9 MHzSymptom:1.	160 M             TX power                  
0 Watts                     1.85     Amps   SWR no reading2.	80M               
TX Power                   0 Watts                     1.85     Amps   SWR
no rea3.	60M                TX Power                   1 Watt                       
2.03    Amps   SWR no rea4.	40M                TX Power                  
1.5 Watts                   2.2       Amps   SWR 1.1-15.	30M               
TX Power                   4.5 Watts                  2.8      Amps   SWR
1.0-1                              Fault code err TxG              Filter
problem?6.	20M                TX power                   10 Watts Max          
4.7       Amps   SWR 1.0-17.	17M                 TX power                  
10 Watts max           4.7       Amps   SWR 1.0-18.	15M                 TX
power                   8 Watts                     4.6       Amps   SWR
1.0-19.	12M                 TX Power                   8 Watts                    
3.9A    Amps   SWR 1.0-110.	10M                 TX Power                   9
Watts                     4.18     Amps   SWR 1.0-111.	6M                  
TX Power                   8 Watts                     2.7       Amps   SWR
1.0-1                              My original MAX RF power was around 16
Watts on all bands except 6MWhat could be effecting the drive on low bands
to fall to zero? and attenuating the RF power on the high bands power?If the
AL 811H (which is not the best engineered amp in the world) provided a
strange match or sent power from self-oscillation back to the K3, what else
could it affect in the K3?RX seems affected to20M, 17M, 12M, 10M and 6M all
give S9 for 50µVLow Bands below at 50µV160M  S580M    S840M    S630M   
S8These all gave S9 before the fault, so a big clue to the faultAny
suggestions where I should start looking, as the RX path is down as well?Is
this the biggest clue (Fault code err TxG) on the 30M band? I have made some
measurements over the weekend and found the followingUsing a scope probe in
to and R & S FSU spectrum analyser I have been tracing signals on 14 MHz
which can give up to 10 Watts, and 1.9 MHz which give zero watts.1.	I have
Checked D26,D31 and D27 they seem to check out and switch.2.	D25 seems to
have a large DC volt drop on RX and TX 0.9 of a volt! Large for a schottky
diode, with 20mA going through, calculated by the volt drop across R48
(should be 0.3V according to the spec sheet)3.	The TX signal is good at W21
on 1.9 and 14 MHz roughly the same. (D1 checks out on a meter)4.	Both
signals are amplified through the LPA to the same level on the drains of Q5
and Q4 FETS, but still no RF power on 1.9 MhzI know A scope probe is not the
best way to measure; what does D1 S1M do on the LPA? Controlled by 12T,
presume a RF O/P switch?6dB attenuator is in all the time.What would stop LF
(1.9 to 10MHz) being amplified?C23 on the LPA board 100PF is missing I
presume this is correct?any suggestion welcome  73's Andrew       



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