K1-4 KAT1: No voltage during SWR bridge adjustment of C9

[KB3OKS - Mark]

Hello everyone,

I'm currently assembling a KAT1 for use with my already-completed K1-4
(which I'd previously been using with an external tuner), and I'm
having some trouble with the final step of the SWR bridge adjustment
of trimmer capacitor C9. I did verify the previous steps of setting
power output to 5.0 watts, attaching a suitable dummy load (same QRP
dummy load I used when aligning the K1), setting both variable
resistors to 60% of their travel, setting the tuner menu options to
'QLS', then entering tune mode and measuring voltage between TP1 and
the ground jumper.

[The problem:]
But I'm getting 0.0 VDC across TP1 and ground. I did remove the KAT1
board and triple check all solder joints, as well as checking for
continuity through my toroid windings. I also checked to make sure
that power was reaching the KAT1 board by measuring about 5.5 VDC
across C17 ... plus the fact that the tuner is 'recognized' by the K1
and all of its menu functions check out as normal.

Does anyone have any tips on something else that I might check, or
could it be that I've actually got a bad trimmer capacitor? I was
unable to find any similar descriptions here.

Thanks for your time, everyone. I absolutely love my K1 and can't wait
to have it be even more portable with its new ATU.

Cheers and 73,

Mark, KB3OKS
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[Don Wilhelm-4]

Mark,

You did try the measurement during transmit did you not?  It will be
zero volts when there is no power going through the wattmeter section of
the tuner.

Check the orientation of the diodes, and check T1 for correct
connections and good tinning of the leads - if you cannot see a bit of
tinned lead above the board, remove T1 and re-tin the leads closer to
the core.  Be certain the single turn of wire (T1 leads 5 and 6) goes
through the center of the toroid.  Make certain that everything is well
soldered, including R2.

You may want to test the diodes for forward and reverse resistances with
your DMM (use the diode check or the ohmmeter function).

Mark Lampert (KB3OKS) wrote:

> Hello everyone,
>
> I'm currently assembling a KAT1 for use with my already-completed K1-4
> (which I'd previously been using with an external tuner), and I'm
> having some trouble with the final step of the SWR bridge adjustment
> of trimmer capacitor C9. I did verify the previous steps of setting
> power output to 5.0 watts, attaching a suitable dummy load (same QRP
> dummy load I used when aligning the K1), setting both variable
> resistors to 60% of their travel, setting the tuner menu options to
> 'QLS', then entering tune mode and measuring voltage between TP1 and
> the ground jumper.
>
> [The problem:]
> But I'm getting 0.0 VDC across TP1 and ground. I did remove the KAT1
> board and triple check all solder joints, as well as checking for
> continuity through my toroid windings. I also checked to make sure
> that power was reaching the KAT1 board by measuring about 5.5 VDC
> across C17 ... plus the fact that the tuner is 'recognized' by the K1
> and all of its menu functions check out as normal.
>
> Does anyone have any tips on something else that I might check, or
> could it be that I've actually got a bad trimmer capacitor? I was
> unable to find any similar descriptions here.
>
> Thanks for your time, everyone. I absolutely love my K1 and can't wait
> to have it be even more portable with its new ATU.
>
> Cheers and 73,
>
>  

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[KB3OKS - Mark]

Don,

The rig was in 'TUN' mode as according to the instructions, but I wasn't actually keying down. Perhaps I missed that?

I checked out T1 but I'll triple check it this evening, and I'll also test the diodes with my DMM since I'm certain of their orientation on the board.

Don Wilhelm wrote

You did try the measurement during transmit did you not?

Check the orientation of the diodes, and check T1 for correct
connections and good tinning of the leads -

You may want to test the diodes for forward and reverse resistances with

[KB3OKS - Mark]

Looks like the problem was the simplest -- I just wasn't in transmit. Sheesh. But better late than never, I suppose. Thanks again for your time, Don ... 73,

Mark / KB3OKS

KB3OKS - Mark wrote

I checked out T1 but I'll triple check it this evening, and I'll also test the diodes with my DMM since I'm certain of their orientation on the board.

Don Wilhelm wrote

You did try the measurement during transmit did you not?

Check the orientation of the diodes, and check T1 for correct
connections and good tinning of the leads -

You may want to test the diodes for forward and reverse resistances with