Intermittent loss of power output K3

classic Classic list List threaded Threaded
7 messages Options
Reply | Threaded
Open this post in threaded view
|

Intermittent loss of power output K3

Peter Lock
Good day

Late last year, my K3 (no 6957) developed a fault.  The symptoms were:
1. No power output when keying the rig
2. TX LED on when keyed, (sidetone generated in CW mode)
3. Single bar showing on the RF power meter, whatever scale, ie 0 - 10 or 0
- 100
4. ATU tune command: relays clicking, TX LED on, no power output, no
indication on SWR meter; two horizontal dashes in the VFO A display area
where normally one would see the resolving SWR; in VFO B area 5.0W is
indicated
5. TX gain calibration failed on 5W and 50W;  mW TX calibration gain OK

I contacted Elecraft Support who suspected a failure of the LPA PA
transistor(s) and I shipped the rig to Watsonville where Q4 on the LPA board
was found to be dead.  Q4 and Q5 were replaced, re-biased and tested.

On getting the rig back, the same symptoms were present, but lasted only a
short while and the rig then performed normally, enough to have a couple of
QSOs, but then failed.  Since then the same symptoms have been present
intermittently.  I asked a friend who also has a K3 to try the rig to make
sure I was not doing something silly.  For about 20 minutes after switch on
the symptoms were present, then for no apparent reason the rig performed
normally for approximately 10 minutes before failing again.  We were testing
by repeatedly invoking ATU tune functions on different bands. Since then,
the rig will work or not work on switch on; it has worked flawlessly for
several hours but sometimes will present only the listed symptoms for
several hours after switch on.

When it is working, it all works, specifically the TX gain calibration
completes normally

After several days of performing normally, I relocated the rig to my
alternative operating location; it did not work, with the same symptoms.

Elecraft Support has been as exemplary as ever, but they are loth for me to
return the rig when it may well sit on the test bench being smug and
behaving normally.  It seems to me that the possibilities are  (i) a dry
solder joint (ii) a loose connection or (iii) a component on the verge of
failing.  I think I should next dismantle and reassemble the rig to try to
exclude option (ii), and perhaps find either (i) or (iii), although needle
and haystack comes to mind...  Has anyone suffered similar problems and
found a solution, or can someone advise where I should concentrate my
search?

Peter
M0RYB



--
Sent from: http://elecraft.365791.n2.nabble.com/
______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: Intermittent loss of power output K3

Elecraft mailing list
 Peter:
This is John Saxon, K5ENQ, in Pearland, TX, and I have experienced what appears to be the identical symptoms.  Also have contacted support, got some suggestions, tried them to no avail (mostly dealing with possible rf grounding issues).  Like you, it may operate perfectly for hours or days, then later I need to ATU and I get the same results as yours when yours fails.  My serial #3524.  Like you I am not inclined to send it in for fear it may not fail.  I also experience these somewhat intermittent failures when loading into a dummy load on my bench.

I am sorry I have nothing useful to convey, other than that you are not alone  :-) 

If anyone does come up with suggestions/solutions, please broadcast to group as there are now at least 2 folks with what appears to be the same issue(s).
Good luck to us all,JohnK5ENQ

    On Friday, March 1, 2019, 8:48:16 AM CST, Peter Lock <[hidden email]> wrote:  
 
 Good day

Late last year, my K3 (no 6957) developed a fault.  The symptoms were:
1. No power output when keying the rig
2. TX LED on when keyed, (sidetone generated in CW mode)
3. Single bar showing on the RF power meter, whatever scale, ie 0 - 10 or 0
- 100
4. ATU tune command: relays clicking, TX LED on, no power output, no
indication on SWR meter; two horizontal dashes in the VFO A display area
where normally one would see the resolving SWR; in VFO B area 5.0W is
indicated
5. TX gain calibration failed on 5W and 50W;  mW TX calibration gain OK

I contacted Elecraft Support who suspected a failure of the LPA PA
transistor(s) and I shipped the rig to Watsonville where Q4 on the LPA board
was found to be dead.  Q4 and Q5 were replaced, re-biased and tested.

On getting the rig back, the same symptoms were present, but lasted only a
short while and the rig then performed normally, enough to have a couple of
QSOs, but then failed.  Since then the same symptoms have been present
intermittently.  I asked a friend who also has a K3 to try the rig to make
sure I was not doing something silly.  For about 20 minutes after switch on
the symptoms were present, then for no apparent reason the rig performed
normally for approximately 10 minutes before failing again.  We were testing
by repeatedly invoking ATU tune functions on different bands. Since then,
the rig will work or not work on switch on; it has worked flawlessly for
several hours but sometimes will present only the listed symptoms for
several hours after switch on.

When it is working, it all works, specifically the TX gain calibration
completes normally

After several days of performing normally, I relocated the rig to my
alternative operating location; it did not work, with the same symptoms.

Elecraft Support has been as exemplary as ever, but they are loth for me to
return the rig when it may well sit on the test bench being smug and
behaving normally.  It seems to me that the possibilities are  (i) a dry
solder joint (ii) a loose connection or (iii) a component on the verge of
failing.  I think I should next dismantle and reassemble the rig to try to
exclude option (ii), and perhaps find either (i) or (iii), although needle
and haystack comes to mind...  Has anyone suffered similar problems and
found a solution, or can someone advise where I should concentrate my
search?

Peter
M0RYB



--
Sent from: http://elecraft.365791.n2.nabble.com/
______________________________________________________________
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
 
______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: Intermittent loss of power output K3

Raymond Sills
In reply to this post by Peter Lock
What happens when the rig is connected to a dummy load?
73 de RayK2ULRKX3 #211


-----Original Message-----
From: John Saxon via Elecraft <[hidden email]>
To: elecraft <[hidden email]>; Peter Lock <[hidden email]>
Sent: Fri, Mar 1, 2019 10:12 am
Subject: Re: [Elecraft] Intermittent loss of power output K3

 Peter:
This is John Saxon, K5ENQ, in Pearland, TX, and I have experienced what appears to be the identical symptoms.  Also have contacted support, got some suggestions, tried them to no avail (mostly dealing with possible rf grounding issues).  Like you, it may operate perfectly for hours or days, then later I need to ATU and I get the same results as yours when yours fails.  My serial #3524.  Like you I am not inclined to send it in for fear it may not fail.  I also experience these somewhat intermittent failures when loading into a dummy load on my bench.

I am sorry I have nothing useful to convey, other than that you are not alone  :-) 

If anyone does come up with suggestions/solutions, please broadcast to group as there are now at least 2 folks with what appears to be the same issue(s).
Good luck to us all,JohnK5ENQ

    On Friday, March 1, 2019, 8:48:16 AM CST, Peter Lock <[hidden email]> wrote: 
 
 Good day

Late last year, my K3 (no 6957) developed a fault.  The symptoms were:
1. No power output when keying the rig
2. TX LED on when keyed, (sidetone generated in CW mode)
3. Single bar showing on the RF power meter, whatever scale, ie 0 - 10 or 0
- 100
4. ATU tune command: relays clicking, TX LED on, no power output, no
indication on SWR meter; two horizontal dashes in the VFO A display area
where normally one would see the resolving SWR; in VFO B area 5.0W is
indicated
5. TX gain calibration failed on 5W and 50W;  mW TX calibration gain OK

I contacted Elecraft Support who suspected a failure of the LPA PA
transistor(s) and I shipped the rig to Watsonville where Q4 on the LPA board
was found to be dead.  Q4 and Q5 were replaced, re-biased and tested.

On getting the rig back, the same symptoms were present, but lasted only a
short while and the rig then performed normally, enough to have a couple of
QSOs, but then failed.  Since then the same symptoms have been present
intermittently.  I asked a friend who also has a K3 to try the rig to make
sure I was not doing something silly.  For about 20 minutes after switch on
the symptoms were present, then for no apparent reason the rig performed
normally for approximately 10 minutes before failing again.  We were testing
by repeatedly invoking ATU tune functions on different bands. Since then,
the rig will work or not work on switch on; it has worked flawlessly for
several hours but sometimes will present only the listed symptoms for
several hours after switch on.

When it is working, it all works, specifically the TX gain calibration
completes normally

After several days of performing normally, I relocated the rig to my
alternative operating location; it did not work, with the same symptoms.

Elecraft Support has been as exemplary as ever, but they are loth for me to
return the rig when it may well sit on the test bench being smug and
behaving normally.  It seems to me that the possibilities are  (i) a dry
solder joint (ii) a loose connection or (iii) a component on the verge of
failing.  I think I should next dismantle and reassemble the rig to try to
exclude option (ii), and perhaps find either (i) or (iii), although needle
and haystack comes to mind...  Has anyone suffered similar problems and
found a solution, or can someone advise where I should concentrate my
search?

Peter
M0RYB



--
Sent from: http://elecraft.365791.n2.nabble.com/
______________________________________________________________
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
 
______________________________________________________________
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
______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: Intermittent loss of power output K3

Elecraft mailing list
 Ray:
I get the same relay chatter, no display of SWR and no output.  Some time later I may do the same ATU and it works.  Appears to do the same thing as when attempting to load an actual antenna.
Because this discussion has begun, I think I will set up again on the bench and see if it will fail. Will be later in the day, I will report results.
--JohnK5ENQ

    On Friday, March 1, 2019, 9:19:43 AM CST, Raymond Sills <[hidden email]> wrote:  
 
 What happens when the rig is connected to a dummy load?
73 de RayK2ULRKX3 #211


 
______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: Intermittent loss of power output K3

Leroy Buller
In reply to this post by Peter Lock
Look at the two diodes in the SWR/watt meter circuit.  These two diode are
critical to the operation of the K3.  These are the foundation of the K3s
ALC implementation.  Ive had to replace them.

Lee K0WA

On Fri, Mar 1, 2019, 8:47 AM Peter Lock <[hidden email]> wrote:

> Good day
>
> Late last year, my K3 (no 6957) developed a fault.  The symptoms were:
> 1. No power output when keying the rig
> 2. TX LED on when keyed, (sidetone generated in CW mode)
> 3. Single bar showing on the RF power meter, whatever scale, ie 0 - 10 or 0
> - 100
> 4. ATU tune command: relays clicking, TX LED on, no power output, no
> indication on SWR meter; two horizontal dashes in the VFO A display area
> where normally one would see the resolving SWR; in VFO B area 5.0W is
> indicated
> 5. TX gain calibration failed on 5W and 50W;  mW TX calibration gain OK
>
> I contacted Elecraft Support who suspected a failure of the LPA PA
> transistor(s) and I shipped the rig to Watsonville where Q4 on the LPA
> board
> was found to be dead.  Q4 and Q5 were replaced, re-biased and tested.
>
> On getting the rig back, the same symptoms were present, but lasted only a
> short while and the rig then performed normally, enough to have a couple of
> QSOs, but then failed.  Since then the same symptoms have been present
> intermittently.  I asked a friend who also has a K3 to try the rig to make
> sure I was not doing something silly.  For about 20 minutes after switch on
> the symptoms were present, then for no apparent reason the rig performed
> normally for approximately 10 minutes before failing again.  We were
> testing
> by repeatedly invoking ATU tune functions on different bands. Since then,
> the rig will work or not work on switch on; it has worked flawlessly for
> several hours but sometimes will present only the listed symptoms for
> several hours after switch on.
>
> When it is working, it all works, specifically the TX gain calibration
> completes normally
>
> After several days of performing normally, I relocated the rig to my
> alternative operating location; it did not work, with the same symptoms.
>
> Elecraft Support has been as exemplary as ever, but they are loth for me to
> return the rig when it may well sit on the test bench being smug and
> behaving normally.  It seems to me that the possibilities are  (i) a dry
> solder joint (ii) a loose connection or (iii) a component on the verge of
> failing.  I think I should next dismantle and reassemble the rig to try to
> exclude option (ii), and perhaps find either (i) or (iii), although needle
> and haystack comes to mind...  Has anyone suffered similar problems and
> found a solution, or can someone advise where I should concentrate my
> search?
>
> Peter
> M0RYB
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
> ______________________________________________________________
> 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
>
______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: Intermittent loss of power output K3

Keith Trinity WE6R
In reply to this post by Peter Lock
Hi Peter;
It definitely had one bad FET on the LPA when it was here, I do not see
in the report that it was intermittent, so I may not have looked closely
for those types of failures.
If you are sure it makes MW power when it is in the failure state, then
it is highly likely the LPA.
Inspect D1 closely, I have seen one side have poor solder, or it can
heat and the solder crystallize. Re-flow solder.
Pull the KPA3 but leave the KPAIO3 riser board and you can run it with
just the LPA.
Disregard errors about KPA3 or set it to "not inst" while you are
working on it.
Then set for several watts (not 5 exactly) and long press XMIT to go
into TUNE, IE transmit a carrier. (TUN PWR must be at "nor").
Then take a stick and tap around on the LPA. Around D1. Also the
green/red enamel on T1 & 2 can fail and the windings can short.
Tap the three bias pots, sometimes they fail internally, or their solder
points.
Look at all parts for solder problems.
You can put it in the fridge and chill it down to encourage failure, or
leave it on for an hour with a blanket over it to heat it up.
Keith WE6R
______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: Intermittent loss of power output K3

Peter Lock
In reply to this post by Peter Lock
Thank you, Keith.
It was indeed a poor solder joint on one end of D1 on the LPA board; there
was a hairline gap between the solder and the terminal of the diode.
Reflowing the solder has cured the problem.
Peter
M0RYB

Hi Peter;
It definitely had one bad FET on the LPA when it was here, I do not see
in the report that it was intermittent, so I may not have looked closely
for those types of failures.
If you are sure it makes MW power when it is in the failure state, then
it is highly likely the LPA.
Inspect D1 closely, I have seen one side have poor solder, or it can
heat and the solder crystallize. Re-flow solder.
Pull the KPA3 but leave the KPAIO3 riser board and you can run it with
just the LPA.
Disregard errors about KPA3 or set it to "not inst" while you are
working on it.
Then set for several watts (not 5 exactly) and long press XMIT to go
into TUNE, IE transmit a carrier. (TUN PWR must be at "nor").
Then take a stick and tap around on the LPA. Around D1. Also the
green/red enamel on T1 & 2 can fail and the windings can short.
Tap the three bias pots, sometimes they fail internally, or their solder
points.
Look at all parts for solder problems.
You can put it in the fridge and chill it down to encourage failure, or
leave it on for an hour with a blanket over it to heat it up.
Keith WE6R



______________________________________________________________
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