[Elecraft] [KX1] Need additional troubleshooting steps for inoperable KXAT1

Sun Mar 15 11:27:20 EDT 2009

Don,

OK, I got the KXAT1 working! Turns out the documentation was right --
the wires *are* numbered correctly. My bad. (Shame on me -- no more late
night soldering for Scott...) I got a rock solid 0.000V calibration null
and the power readings are within 0.1 watt of what I'm getting from the
DL1. Now it looks like all I need to do is build an antenna and wire the
stereo plug to my J-38 key. Then it's play time!

So, thanx again, Don!

Scott
AC0FQ

Scott Wright wrote:
> Don,
>
> Thanx for your reply!
>
> "When viewed as in the diagram, the leads coming off the core closest to
> you are numbered 2 and 4..."
>
> That's gotta' be the problem then.  In my documentation, those two wires
> are labeled as 1&3.  Had they been labeled as 2&4, I would have had the
> "clean, drop-in install" I referred to in my original e-mail.  Couple
> that with the informational statement, "...the wires labeled (1) and (3)
> should originate from below the core...", it was easy to convince myself
> that such a bizarre lead routing alignment was necessary.
>
> Oof dah...
>
> OK, I'm off to unsolder T1 and try to get it installed correctly.  I'll
> let you know what results.
>
> Again, thanx for the pointers!
>
> Scott
> AC0FQ
>
>
> Don Wilhelm wrote:
>   
>> Scott,
>>
>> The problem lies with #4 and #7 below.
>> Look carefully at the diagram of T1 on page 5 of the KXAT1
>> instructions.  If yours looks 'backwards', then it may be wound in the
>> wrong sense.  When viewed as in the diagram, the leads coming off the
>> core closest to you are numbered 2 and 4, and the turns from that end
>> progress clockwise around the core.
>> If you have the sense 'backwards', the leads will cross over under the
>> core when it is mounted - that is not what should happen.  If you have
>> it right, the leads will drop straight down from the core onto the
>> board when it is mounted.
>>
>> Yes, all the T1 leads will appear to be shorted together after T1 is
>> installed - that is not a valid check.
>>
>> If everything is correct, you will find a deep null when adjusting the
>> capacitor.  The voltage at the null point should be in the tens of
>> millivolt range.  If you do not find the null, then look for something
>> wrong with T1, C9, C10, R4 or R5.  Also check the orientation of D1
>> and D2.
>>
>> Do not attempt power or SWR calibration until after you can achieve a
>> good null - all attempts to do so will lead to frustration and
>> incorrect results.
>>
>> 73,
>> Don W3FPR
>>
>>
>> Scott Wright wrote:
>>     
>>> I'm having trouble with my KXAT1.  More specifically, (1) I can't get
>>> the power reading to adjust up to anywhere near the actual TX power and
>>> (2) the SWR reading with the DL1 dummy load attached is 9.9, which I
>>> assume is not a good thing.
>>>
>>> Here are the data bits:
>>>
>>> 1)  There's no 30/80m module.
>>>
>>> 2)  I ohm'ed out the DL1 and it reads 50.1 ohms.  Close enough.
>>>
>>> 3)  With the R1 pot set at ~50%, the KX1's power display is 0.7 watts in
>>> 'tun' mode.  The power reading at the DL1 is 3.6 watts, which is pretty
>>> much the same reading I got after I finished the KX1's transmit section
>>> (before adding the AT).  Cranked fully CW (?), the maximum displayed
>>> power reading is 2.1 watts on the KX1.
>>>
>>> 4)  During calibration, nulling the voltage on the REFL test point
>>> results in a voltage of approx 1.75 volts.  I've seen posts on the
>>> reflector where folks are getting nulls well below 1V.  I suppose this
>>> isn't a good thing, either...
>>>
>>> 5)  I ohm'ed inductors L1, L2, and L3 after installation and all three
>>> read <0.3 ohms.  I'll assume that means good
>>> stripping/tinning/soldering.
>>>
>>> 6)  I tried ohm'ing transformer T1 after it was installed to see if I
>>> had any shorts but I'm reading <0.3 ohms across any combination of
>>> leads.  This (sorta') makes sense -- given how it's gonna' react to DC
>>> -- but doesn't tell me anything.
>>>
>>> 7)  I quadruple checked my installation of T1.  The picture and notes in
>>> the assembly manual are a bit confusing and unlike all other Ls and Ts
>>> I've installed so far, the footprint/silkscreen for T1 doesn't line up
>>> with how the winding is described.  What looks like a clean, drop-in
>>> install results in -- as I read it -- incorrect phasing.  Matching T1's
>>> wiring diagram / picture to its silkscreen forces the leads to run under
>>> the toroid in a "contorted" fashion.  As ugly as it was going in, that's
>>> how I have it soldered in place.
>>>
>>> 8)  When instructed to tune, the resultant SWR is always displayed as
>>> 9.9.  (I can hear the relays clicking on-and-off in rapid succession
>>> during the tune...)  I tried the inductor/capacitor test outlined in the
>>> KXAT1's troubleshooting guide, but regardless of the L0/1/2/3 or
>>> C0/1/2/3 setting, the SWR always displays as 9.9
>>>
>>> So, I'm at an impasse.  I don't wanna' start randomly removing
>>> components -- I haven't yet had to remove a single component from the
>>> KX1 or the AT -- but I'm at a loss as to what to do next.
>>>
>>> Are there any other troubleshooting steps??  I'll never claim to be a
>>> guru on this stuff -- in fact, I'm not 100% certain how an AT even works
>>> -- so any additional guidance would be greatly appreciated.
>>>
>>> Thanx!!
>>>
>>> Scott
>>> AC0FQ
>>> KX1 s/n 2177
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