A K1 problem

[David L DuPuy]

My K1 (20m + 40m), built about five months ago, has been operating
perfectly...  after some initial problems which were resolved.  I’ve
recently taken it camping and a roadblock problem has now showed up (on two
earlier camping trips, it performed well).

The symptoms are twofold: first, there is no sidetone when keyed, although
I can see the bars on the LCD as the transmitter is keyed.  I am using it
with separate 20 and 40 dipoles dipoles and no antenna tuner (which worked
nicely before this).

Second, the incoming signals are extremely weak and have a very strange
sound as if the narrowest filter were engaged (it’s not).  This prompted me
to think it was an antenna problem and I have tried both 40m and 20m
camping dipoles, and I checked the coax from inside the camper to outside.
 Further, I brought the K1 inside the house to use with my home antenna
(with all aspects of the antenna and feedline different than used in the
camper), and the problem is the same.  So it’s a problem inside the K1.

I wondered if “faulty antenna connection” (or something similar) might be
the problem.  Is there a provision for the K1 to shutdown if keyed with no
antenna?  I have inspected the RF board carefully and can find no visual
problems.  Likewise for the filter board.  I have also replaced the
BNC-to-UHF cable, the problem is still there.

An important clue: while camping, when the problem showed up, one of the
screws holding the speaker had come loose, and I’ve just discovered the nut
had been floating around on the RF board, and was wedged in between the
case and U5 (8-volt 3-pin regulator IC).  I’ve checked the output of U5 and
it’s 8.0 volts, so that’s not the problem.  The VFO is working correctly.
 I have to wonder what else that loose nut might have shorted out.

Does anyone have any ideas on troubleshooting this?  I greatly appreciate
any suggestions.  Many thanks, David AC4BN
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[Mike Morrow-3]

David/AC4BN wrote:

>The symptoms are twofold: first, there is no sidetone when keyed, although
>I can see the bars on the LCD as the transmitter is keyed.  I am using it
>with separate 20 and 40 dipoles dipoles and no antenna tuner (which worked
>nicely before this).
>
>Second, the incoming signals are extremely weak and have a very strange
>sound as if the narrowest filter were engaged (it’s not).

1.  Are you observing these problems through the speaker?  Have you
determined that the audio sounds as poorly through headphones (or another
speaker) that has been connected through the phone jack?  This information
could rule out a simple AF jack problem.

2.  Doer an external power meter indicate normal power out when the K1
is keyed?  Does an external receiver hear a normal signal when the K1
is keyed?

73,
Mike / KK5F
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[Don Wilhelm-4]

David,

Loss of sidetone as well as 'strangness' in the filter width points to
the XFIL/TONE signal line which originates at pin 1 of Front Panel U2.  
It provides sidetone during transmit and the voltage during receive
controls the width of the IF filter.

I don't know if it could be directly related to the loose nut, screw and
washers, but it certainly could be possible that some of that hardware
could have shorted the XFIL/TONE, but look for washers around the
connector between the front panel and the RF board.  If you are lucky,
retieving those parts will set things back to normal, but there is a
chance that a short on that line could have wiped out the pin 1 output
if FP U2.

73,
Don W3FPR

On 7/1/2013 4:38 PM, David L DuPuy wrote:

> My K1 (20m + 40m), built about five months ago, has been operating
> perfectly...  after some initial problems which were resolved.  I’ve
> recently taken it camping and a roadblock problem has now showed up (on two
> earlier camping trips, it performed well).
>
> The symptoms are twofold: first, there is no sidetone when keyed, although
> I can see the bars on the LCD as the transmitter is keyed.  I am using it
> with separate 20 and 40 dipoles dipoles and no antenna tuner (which worked
> nicely before this).
>
> Second, the incoming signals are extremely weak and have a very strange
> sound as if the narrowest filter were engaged (it’s not).  This prompted me
> to think it was an antenna problem and I have tried both 40m and 20m
> camping dipoles, and I checked the coax from inside the camper to outside.
>   Further, I brought the K1 inside the house to use with my home antenna
> (with all aspects of the antenna and feedline different than used in the
> camper), and the problem is the same.  So it’s a problem inside the K1.
>
> I wondered if “faulty antenna connection” (or something similar) might be
> the problem.  Is there a provision for the K1 to shutdown if keyed with no
> antenna?  I have inspected the RF board carefully and can find no visual
> problems.  Likewise for the filter board.  I have also replaced the
> BNC-to-UHF cable, the problem is still there.
>
> An important clue: while camping, when the problem showed up, one of the
> screws holding the speaker had come loose, and I’ve just discovered the nut
> had been floating around on the RF board, and was wedged in between the
> case and U5 (8-volt 3-pin regulator IC).  I’ve checked the output of U5 and
> it’s 8.0 volts, so that’s not the problem.  The VFO is working correctly.
>   I have to wonder what else that loose nut might have shorted out.
>
> Does anyone have any ideas on troubleshooting this?  I greatly appreciate
> any suggestions.  Many thanks, David AC4BN
>

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