http://elecraft.85.s1.nabble.com/K2-Debugging-low-transmit-power-tp5601987p5605929.html
the Transmit Signal Tracing. The K2 itself is the signal generator for
answer to your problems. Count the turns on the toroids carefully. A
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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