http://elecraft.85.s1.nabble.com/K2-Debugging-low-transmit-power-tp5601987p5607676.html
couple of anomalies. I'm referencing the specific section name and
3. Pin 2 of U8 (on the control board) shows 4.97VDC instead of the
expected .7 - 2.5VDC. The manual tells me to check the component
values in the RF detector, which I have. They are all correct.
2. Pin 4 of U10 shows .228 Vrms instead of the expected .016.
3. Pin 6 of U9 shows 1.148 Vrms instead of .2.
4. W6 shows 0.
5. D1 shows 0.
So those seem _totally_ out of whack. These checks were done on 40m,
which is where I'm having problems. Now what?
(Owen B. Mehegan)
> Owen,
>
> You should not need a signal generator for Transmit Signal Tracing -
> I believe you are in the Receive Signal Tracing area - skip that and
> go to the Transmit Signal Tracing. The K2 itself is the signal
> generator for this TX signal tracing.
>
> Try increasing the CAL CUR setting to 3.50 Amps rather than the
> manual suggested setting of 2.50 amps.
> Often the 80 meter output will be well above the 15 watt level, and
> the current needed for that higher power output will be in excess of
> the 2.50 Amp setting.
>
> If the Hi-Cur messages persist, then look to the Low Pass filter for
> the answer to your problems. Count the turns on the toroids
> carefully. A problem with Hi-Cur coupled with low power output is
> normally an indication of a problem with either T4 or the Low Pass
> filter.
>
> 73,
> Don W3FPR
>
> On 10/6/2010 1:42 AM, Owen B. Mehegan wrote:
>> Thanks again for the suggestions Don. Tonight I started doing some
>> signal tracing, and my RF probe seems to work fine with my DMM.
>> However, I ran up against a different obstacle: I don't have a signal
>> generator handy, and the LPF/BPF/T-R Switch tests seem to require
>> one.
>> I can get access to one but it won't be until tomorrow at least.
>>
>> I did find one other data point for my symptoms. On SOME bands, I get
>> the expected power out when I put the K2 into tune mode. Here are the
>> results of my tests:
>>
>> 80m sometimes shows "high cur" the first time I test, then I quickly
>> turn off tune, then try again and I see a normal reading
>> 40m always too low
>> 30m same as 80m
>> 20m OK
>> 17m OK
>> 15m OK
>> 12m too low
>> 10m too low
>>
>> I checked continuity on all my toroids, from "pad to pad" instead of
>> lead to lead, as far as I was able. Everything seems to check out
>> there. I'm not sure I can do anything else without a signal
>> generator,
>> but I'm open to suggestions.
>>
>> --
>>
[hidden email] (Owen B. Mehegan)
>> 'This above all: to thine own self be true,
>> And it must follow, as the night the day,
>> Thou canst not then be false to any man.'
>> --William Shakespeare
>>
>> On Oct 5, 2010, at 7:01 AM, Don Wilhelm wrote:
>>
>>> Owen,
>>>
>>> I am going to assume that you were successful with the Alignmant and
>>> Test Part II and were able to receive 40 meter signals. If not, you
>>> need to backtrack a bit and get receive working first.
>>>
>>> The easiest way to troubleshoot a "lack of power output" problem is
>>> to do Transmit Signal Tracing. You can use an RF Probe or an
>>> oscilloscope with a 10X probe.
>>>
>>> Turn the manual to the Appendix E section titled Transmit Signal
>>> Tracing and begin there. If using an RF Probe, the correct expected
>>> values are listed, but if using an oscilloscope, multiply those
>>> values by 2.8 and observe the peak to peak voltage of the RF
>>> waveform.
>>>
>>> An important note - the K2 will normally increase drive in an
>>> attempt to increase the power output if the voltage out of the RF
>>> detector is too small. What that means is that all RF voltages
>>> prior to the failing stage the RF voltages will be higher than the
>>> listed expected values. You will be investigating the transmit
>>> chain in the order listed (do not skip around), searching for the
>>> *first* stage where the output is lower than expected - that is the
>>> failing stage which then needs to be analyzed to determine why it is
>>> not operating properly. Measurements beyond this first failure
>>> point are not relevant to that first problem to be found.
>>> All RF Voltage measurements in the list can be done from the top of
>>> the RF Board. Do not transmit with the heat sink removed. If the
>>> PA transistors do get a bit of drive, will produce output and if the
>>> heat sink is not in place, they will quickly overheat and fry
>>> themselves.
>>>
>>> Normal failures are soldering problems, toroid leads or incorrectly
>>> placed components. Active device failures are way down of the list
>>> of failure suspects unless something has caused it to be abused.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>> On 10/5/2010 2:38 AM, Owen B. Mehegan wrote:
>>>> Hello -
>>>>
>>>> Two nights ago I completed the assembly of my K2's RF board, and
>>>> after
>>>> a visual inspection verification of resistance checks, I assembled
>>>> the
>>>> radio per the instructions and began the third phase of alignment
>>>> and
>>>> test. I've discovered a problem right off the bat, though. In the
>>>> 40
>>>> meter transmitter alignment section, when I put the K2 into tune
>>>> mode
>>>> at 2 watts power, I'm only reading .3-.4 watts on the onboard
>>>> wattmeter (it alternates between the two). This is with a
>>>> connection
>>>> to a 100W dummy load. Varying L1 and L2 has no effect on the power
>>>> reading.
>>>>
>>>> I discovered one mistake: I misread the instructions for winding
>>>> T4's
>>>> 5-6 and 7-8 windings. I wound these bare wires through BOTH holes
>>>> in
>>>> the core, in a U shape, thus connecting 6-7 and 5-8 (and very
>>>> possibly
>>>> all 4 together with a short in the middle - this is what comes of
>>>> staying up too late working on a project!). I corrected this
>>>> mistake
>>>> tonight, but I'm seeing no change on the measured power. Is it
>>>> possible that this mistake fried something? I never saw any smoke
>>>> or
>>>> smelled burned silicon, and the thermal pads on Q7 and Q8 look
>>>> normal.
>>>>
>>>> I have also noticed that if I vary the power adjustment on the
>>>> front
>>>> panel while in tune mode, I see no change on the wattmeter. That
>>>> seems
>>>> significant.
>>>>
>>>> These are the other checks I've done so far, per the
>>>> troubleshooting
>>>> instructions:
>>>>
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