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

[Don Wilhelm]

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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