K1 with a strange XFIL problem...

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K1 with a strange XFIL problem...

Bruce Beford-2
OK, folks.
Time to put on your thinking caps...
I just purchased a used K1. Has NB, ATU and 4 band board, set for
7/10.1/14/21 MHz. All appears to be operating normally, except...
When cycling through the crystal filter bandwidths from FL1-FL3, once FL3 is
reached, all buttons become unresponsive. The VFO readout still works, but
the MCU will not respond to any key presses. The filter does actually switch
to the narrowest setting, based on the audio response. Cycling the power
returns the rig to normal operation (on FL1), and all works fine again until
trying to use FL3.

About the only other anomaly I notice is what seems to be a louder pop in
the speaker when switching in RIT or XIT than I remember from my last K1. I
have not yet begun any troubleshooting (except for a full reset). Just
thought I would poll the collective wisdom here before digging in. Actually,
I'll be getting ready for Lobstercon over the next couple of days, so I
don't know how much time I'll be able to commit until after the weekend.

I'd appreciate any thoughts or ideas on this one.
Thanks es 72/73,
Bruce, N1RX


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Re: K1 with a strange XFIL problem...

Don Wilhelm-4
Bruce,

There is nothing overtly associated with the selection of FL3 that
*should* cause a lockup.  The way the bandwidth is controlled is to vary
the voltage of the XFIL/TONE signal from the D/A converter - front panel
U2 and apply it to the varactors connected to the filter crystals.

I suspect that you have a corrupt bit(s) in EEPROM. You will have to do
all the VFO, SIG and other menu calibration steps, but you can try a
Reset to Firmware Defaults - see page 57 of the K1 manual.

But then I see that you have tried that - so perhaps a new firmware IC
is in order - that is just a guess, but the best firmware
troubleshooting tool is substitution.  You could also try replacing
Front Panel U2 and U3 along with U1.

73,
Don W3FPR

On 7/2/2012 5:36 PM, Bruce Beford wrote:

> OK, folks.
> Time to put on your thinking caps...
> I just purchased a used K1. Has NB, ATU and 4 band board, set for
> 7/10.1/14/21 MHz. All appears to be operating normally, except...
> When cycling through the crystal filter bandwidths from FL1-FL3, once FL3 is
> reached, all buttons become unresponsive. The VFO readout still works, but
> the MCU will not respond to any key presses. The filter does actually switch
> to the narrowest setting, based on the audio response. Cycling the power
> returns the rig to normal operation (on FL1), and all works fine again until
> trying to use FL3.
>
> About the only other anomaly I notice is what seems to be a louder pop in
> the speaker when switching in RIT or XIT than I remember from my last K1. I
> have not yet begun any troubleshooting (except for a full reset). Just
> thought I would poll the collective wisdom here before digging in. Actually,
> I'll be getting ready for Lobstercon over the next couple of days, so I
> don't know how much time I'll be able to commit until after the weekend.
>
> I'd appreciate any thoughts or ideas on this one.
> Thanks es 72/73,
> Bruce, N1RX
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>


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Re: K1 with a strange XFIL problem...

ae6rq
Hi all -

I wonder if this problem has ever been resolved?  I have had the same issue for several years with mine (serial number 278, previously owned by K8RA who reported the same problem.)  

http://elecraft.365791.n2.nabble.com/On-a-K1-how-do-I-get-back-from-FL3-to-FL1-or-FL2-Menu-freezes-td7570579.html

http://marc.info/?l=elecraft&m=105624414018316&w=2

and the thread to which I reply now:  http://elecraft.365791.n2.nabble.com/K1-with-a-strange-XFIL-problem-tp7558513p7558526.html 

72/73
Dave
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Re: K1 with a strange XFIL problem...

ae6rq
Success!

Thanks to Bruce N1RX for his knowledge and prior troubleshooting to resolve this issue.  

RIT/XIT switch -


What he described and photographed (above) are exactly the cause of this problem. The RIT switch leg was making contact with pin 5 of J1.


72/73
Dave




For further details, please see Bruce's reply to me below:  


Yes I had this exact problem on one I repaired in July of 2012. It was
traced to a short between the RIT/XIT switch to a trace on the board, where
the switch lead had been bent over by the original builder before soldering.

I corresponded with Don Wilhelm about this. Though he didn't provide the
solution, our conversation led me to the tests that found it. Copied below
is  a repost of my last message to Don, after I resolved it. I don't recall
if I posted this to the reflector or not. In any event, It may help someone
in the future. I have a photo of the offending switch pin connection, if
anyone wants it.
Bruce Beford, N1RX

Hi, Don.
You may recall that I posted recently to the list about a strange problem
with a K1.  I resolved it today, and wanted to share the results with you.
Here's a copy of my original post:

OK, folks.
Time to put on your thinking caps...
I just purchased a used K1. Has NB, ATU and 4 band board, set for
7/10.1/14/21 MHz. All appears to be operating normally, except...
When cycling through the crystal filter bandwidths from FL1-FL3, once FL3 is
reached, all buttons become unresponsive. The VFO readout still works, but
the MCU will not respond to any key presses. The filter does actually switch
to the narrowest setting, based on the audio response. Cycling the power
returns the rig to normal operation (on FL1), and all works fine again until
trying to use FL3.

About the only other anomaly I notice is what seems to be a louder pop in
the speaker when switching in RIT or XIT than I remember from my last K1. I
have not yet begun any troubleshooting (except for a full reset). Just
thought I would poll the collective wisdom here before digging in. Actually,
I'll be getting ready for Lobstercon over the next couple of days, so I
don't know how much time I'll be able to commit until after the weekend.

----------------------------------------------------------------------------

You and I both suspected a problem with the MCU, as there should no other
circuitry involved, except the DAC and EEPROM. You also suggested perhaps
replacing those ICs while in there.

Fortunately, I have a friend who allowed me to borrow his working K1.
Swapped the entire Front Panel board, mine works fine with his board. I then
took his MCU chip and put it in my board, still have the problem. So, the
problem was on my FP board, but not the MCU.

One thing I did notice was a ticking noise in the audio with no antenna
connected, almost like ignition noise in a vehicle, when using my board FP
board but not when using my friend's. The ticking would disappear when I
went to FL2. Ahh, another clue...

I then decided to remove the DAC from my board and see what happens. Lo, The
unit would now switch properly, FL3,FL2,FL1 and back to FL3 OK. Of course,
it was not actually switching the filter bandwidth with the DAC out. I now
had a pretty load, almost moterboating noise in the audio.

I decided to ground what was the XFIL/TONE output pin of the DAC (pin 1) to
see if it would quiet the audio. It did, BUT- it activated the RIT! Wait a
minute- there should be no connection between the two.... but, there was.
Upon extra careful inspection, I found that one lead on the RIT/XIT switch
was not inserted through the board by the original builder. It was bent
over, and was contacting pin 5 on J1 (the XFIL/TONE signal). The
"moaterboating" I heard was actually the MCU driving the LCD pin and polling
the input for the switch. This was not noticeable when the DAC was holding
this line at a steady DC voltage.

So, what was happening was when the DAC output it's lowest voltage for FL1
(about 1.6 volts), it would tickle the input pin on the MCU for the
WPM+/FILTER switch. I believe the MCU would think the switch was being held
in, therefore no other switches would work, until the unit was powered off.
An original symptom (which I didn't recognize at the time) was when I noted
that the RIT/XIT button seemed to generate an audio pop when used. That's
because it was grounding the XFIL/TONE signal line.

I reworked the switch connection, and all is fine now. I have attached a
photo of the offending pin (not  a good shot, but shows the connection in
question). I thought you might like to hear about this one.

Thanks for being a "sounding board", Don. I appreciate it.
73,
Bruce, N1RX