Elecraft

[K2] Odd AGC problem with K60XV installed

Classic

List

Threaded

10 messages Options

Bill Coleman-2

[K2] Odd AGC problem with K60XV installed

A few weeks ago, I managed to cobble enough of the parts together to build a K60XV. It came together great, and works both on 60m as well as a base for a transverter.

I thought that would have been the happy end of the story, except I’ve had some odd trouble with it installed. I saw this briefly the day after the SS CW contest, and on the second day of the SS Phone contest. In each case, removing the K60XV solved the problem and it did not recur.

Here’s what I’ve observed. After leaving the K2/100 turned on for several hours, the rig is in receive mode, but the AGC is fully activated, with all ten bars showing on the S-meter. The receiver audio is entirely blanked.

This condition is intermittent and random. It tends to last for several seconds to many minutes. It happens on all bands at the same time EXCEPT it does NOT happen on any TRN band that is configured (I have one configured for 50 MHz/28 MHz). This lead me to believe the K60XV was involved. During the SS Phone, I removed the K60XV and replaced it with a Re-work eliminator and K2/100 and the rig worked just fine for the next 10 hours.

During the last three days, I opened the K2 up and laid the KPA100 on the workbench and left the K2 powered up with the K60XV installed. The problem manifested itself within hours. I was able to run a few diagnostics.

The AGC activation happens in all all AGC modes, SLO, FAST and OFF. I was able to get a scope probe on the emitter of Q12 on the Control board. When the blanking occurs, I see a train of pulses around 2 mS apart - around 500 Hz.

I tried poking a finger around various places on the K60XV board to try to exacerbate the problem. I wasn’t able to determine anything conclusive, although a couple of times I thought something in the vicinity of the K2 relay might be involved.

I’m completely dumbfounded by this problem. There’s nothing in the K60XV that interconnects with the AGC system in any way. What could possibly be going on here?

Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901

______________________________________________________________
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
Message delivered to [hidden email]

Don Wilhelm

Re: [K2] Odd AGC problem with K60XV installed

Bill,

You might want to inspect the K60XV soldering carefully for bridges and
anything unsoldered.

When this fault condition occurs, what is the voltage on K60XV P1 pin 6.
If VRFDET becomes active during receive, the K2 may behave as you
describe because the firmware 'thinks' the K2 is transmitting. The fact
that you do not see it on the transverter bands further amplifies my
thoughts on the source of the problem being the VRFDET signal.

I cannot think of a component problem that would create your condition,
so that is why I asked you to review the soldering. Look at the
component placement too - make sure all the components are in the right
hole and not in a nearby via hole. Check D3 and D4 for proper orientation.

73,
Don W3FPR

On 11/28/2020 5:21 PM, Bill Coleman wrote:

> A few weeks ago, I managed to cobble enough of the parts together to build a K60XV. It came together great, and works both on 60m as well as a base for a transverter.
>
> I thought that would have been the happy end of the story, except I’ve had some odd trouble with it installed. I saw this briefly the day after the SS CW contest, and on the second day of the SS Phone contest. In each case, removing the K60XV solved the problem and it did not recur.
>
> Here’s what I’ve observed. After leaving the K2/100 turned on for several hours, the rig is in receive mode, but the AGC is fully activated, with all ten bars showing on the S-meter. The receiver audio is entirely blanked.
>
> This condition is intermittent and random. It tends to last for several seconds to many minutes. It happens on all bands at the same time EXCEPT it does NOT happen on any TRN band that is configured (I have one configured for 50 MHz/28 MHz). This lead me to believe the K60XV was involved. During the SS Phone, I removed the K60XV and replaced it with a Re-work eliminator and K2/100 and the rig worked just fine for the next 10 hours.
>
> During the last three days, I opened the K2 up and laid the KPA100 on the workbench and left the K2 powered up with the K60XV installed. The problem manifested itself within hours. I was able to run a few diagnostics.
>
> The AGC activation happens in all all AGC modes, SLO, FAST and OFF. I was able to get a scope probe on the emitter of Q12 on the Control board. When the blanking occurs, I see a train of pulses around 2 mS apart - around 500 Hz.
>

______________________________________________________________
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
Message delivered to [hidden email]

Bill Coleman-2

Re: [K2] Odd AGC problem with K60XV installed

Thanks, Don, I’ll check it out when I have a chance next week. I appreciate your suggestions. At the moment, the K60XV and the K2 are about 35 miles apart….

> On Nov 28, 2020, at 5:53 PM, Don Wilhelm <[hidden email]> wrote:
>
> Bill,
>
> You might want to inspect the K60XV soldering carefully for bridges and anything unsoldered.
>
> When this fault condition occurs, what is the voltage on K60XV P1 pin 6. If VRFDET becomes active during receive, the K2 may behave as you describe because the firmware 'thinks' the K2 is transmitting. The fact that you do not see it on the transverter bands further amplifies my thoughts on the source of the problem being the VRFDET signal.
>
> I cannot think of a component problem that would create your condition, so that is why I asked you to review the soldering. Look at the component placement too - make sure all the components are in the right hole and not in a nearby via hole. Check D3 and D4 for proper orientation.
>
> 73,
> Don W3FPR
>
> On 11/28/2020 5:21 PM, Bill Coleman wrote:
>> A few weeks ago, I managed to cobble enough of the parts together to build a K60XV. It came together great, and works both on 60m as well as a base for a transverter.
>> I thought that would have been the happy end of the story, except I’ve had some odd trouble with it installed. I saw this briefly the day after the SS CW contest, and on the second day of the SS Phone contest. In each case, removing the K60XV solved the problem and it did not recur.
>> Here’s what I’ve observed. After leaving the K2/100 turned on for several hours, the rig is in receive mode, but the AGC is fully activated, with all ten bars showing on the S-meter. The receiver audio is entirely blanked.
>> This condition is intermittent and random. It tends to last for several seconds to many minutes. It happens on all bands at the same time EXCEPT it does NOT happen on any TRN band that is configured (I have one configured for 50 MHz/28 MHz). This lead me to believe the K60XV was involved. During the SS Phone, I removed the K60XV and replaced it with a Re-work eliminator and K2/100 and the rig worked just fine for the next 10 hours.
>> During the last three days, I opened the K2 up and laid the KPA100 on the workbench and left the K2 powered up with the K60XV installed. The problem manifested itself within hours. I was able to run a few diagnostics.
>> The AGC activation happens in all all AGC modes, SLO, FAST and OFF. I was able to get a scope probe on the emitter of Q12 on the Control board. When the blanking occurs, I see a train of pulses around 2 mS apart - around 500 Hz.

Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901

______________________________________________________________
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
Message delivered to [hidden email]

Don Wilhelm

Re: [K2] Odd AGC problem with K60XV installed

Bill,

It is also a mystery to me that it is intermittent rather than a solid
failure. That might imply that something is breaking into oscillation
and overwhelming the VRFDET line. That is why I suggested you check the
component placement and the diode orientation.
That intermittent condition can also be caused by a soldering problem
that takes some time to appear.

For the non-transverter bands, it is only necessary that the 4.7pF
capacitor be in the circuit and that relay K1 be in the reset position.

If you hear a relay click when this problem starts, then look to the
firmware on the K60XV to make sure all its related components are in
place - there are not many. If you do hear the relay click, one thing
you can do is to arbitrarily replace the resonator. While I have never
seen an intermittent resonator (dead one = yes), it is one possibility.

73,
Don W3FPR

On 11/28/2020 5:59 PM, Bill Coleman wrote:
> Thanks, Don, I’ll check it out when I have a chance next week. I appreciate your suggestions. At the moment, the K60XV and the K2 are about 35 miles apart….
>
>

______________________________________________________________
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
Message delivered to [hidden email]

Bill Coleman-2

Re: [K2] Odd AGC problem with K60XV installed

Don,

I set the K2 up this weekend to try to reproduce this problem. Once again I opened it up and re-installed the K60XV board. I put a scope probe on P1 pin 6.

I did not see the AGC failure mode right away, but I did find an intermittent oscillation on pin 6 at about 15 MHz. It would come and go, but no AGC activation.

I removed the board and re-soldered all the components around the LM358. Then I inspected the board and scraped away any residual solder flux in that area of the board between any pins.

I also re-soldered the 4.0 MHz resonator, although I did not hear or detect any relay activation when it failed before.

After that, I put the board back in with the scope probe and ran it on the workbench for a day. I saw no AGC failure mode and no more 15 MHz oscillation.

So, maybe it is fixed? Fingers crossed.

> On Nov 28, 2020, at 6:19 PM, Don Wilhelm <[hidden email]> wrote:
>
> Bill,
>
> It is also a mystery to me that it is intermittent rather than a solid failure. That might imply that something is breaking into oscillation and overwhelming the VRFDET line. That is why I suggested you check the component placement and the diode orientation.
> That intermittent condition can also be caused by a soldering problem that takes some time to appear.
>
> For the non-transverter bands, it is only necessary that the 4.7pF capacitor be in the circuit and that relay K1 be in the reset position.
>
> If you hear a relay click when this problem starts, then look to the firmware on the K60XV to make sure all its related components are in place - there are not many. If you do hear the relay click, one thing you can do is to arbitrarily replace the resonator. While I have never seen an intermittent resonator (dead one = yes), it is one possibility.
>
> 73,
> Don W3FPR
>
> On 11/28/2020 5:59 PM, Bill Coleman wrote:
>> Thanks, Don, I’ll check it out when I have a chance next week. I appreciate your suggestions. At the moment, the K60XV and the K2 are about 35 miles apart….
>>
>>
>

Don Wilhelm

Re: [K2] Odd AGC problem with K60XV installed

Bill,

It does sound like it is fixed. Just be aware that some intermittents
do find their way back, so knowing the symptoms you can recognize it
quickly.

73,
Don W3FPR

On 12/6/2020 6:30 PM, Bill Coleman wrote:

> Don,
>
> I set the K2 up this weekend to try to reproduce this problem. Once again I opened it up and re-installed the K60XV board. I put a scope probe on P1 pin 6.
>
> I did not see the AGC failure mode right away, but I did find an intermittent oscillation on pin 6 at about 15 MHz. It would come and go, but no AGC activation.
>
> I removed the board and re-soldered all the components around the LM358. Then I inspected the board and scraped away any residual solder flux in that area of the board between any pins.
>
> I also re-soldered the 4.0 MHz resonator, although I did not hear or detect any relay activation when it failed before.
>
> After that, I put the board back in with the scope probe and ran it on the workbench for a day. I saw no AGC failure mode and no more 15 MHz oscillation.
>
> So, maybe it is fixed? Fingers crossed.
>
>

Bill Coleman-2

Re: [K2] Odd AGC problem with K60XV installed

I’m going to set it up in the damp basement at my other QTH. That’s where I saw the problem originally. Will let you know if it comes back.

> On Dec 7, 2020, at 11:43 AM, Don Wilhelm <[hidden email]> wrote:
>
> Bill,
>
> It does sound like it is fixed. Just be aware that some intermittents do find their way back, so knowing the symptoms you can recognize it quickly.
>
> 73,
> Don W3FPR
>
> On 12/6/2020 6:30 PM, Bill Coleman wrote:
>> Don,
>>
>> I set the K2 up this weekend to try to reproduce this problem. Once again I opened it up and re-installed the K60XV board. I put a scope probe on P1 pin 6.
>>
>> I did not see the AGC failure mode right away, but I did find an intermittent oscillation on pin 6 at about 15 MHz. It would come and go, but no AGC activation.
>>
>> I removed the board and re-soldered all the components around the LM358. Then I inspected the board and scraped away any residual solder flux in that area of the board between any pins.
>>
>> I also re-soldered the 4.0 MHz resonator, although I did not hear or detect any relay activation when it failed before.
>>
>> After that, I put the board back in with the scope probe and ran it on the workbench for a day. I saw no AGC failure mode and no more 15 MHz oscillation.
>>
>> So, maybe it is fixed? Fingers crossed.
>>
>>
>

Bill Coleman-2

Re: [K2] Odd AGC problem with K60XV installed

Don,

Just a quick follow-up. I’m going to close the book on this problem, as it has not come up again, despite leaving the K2 on a couple of days.

I think your diagnoses was spot on, I think a 15 MHz oscillation of the K60XV VRFDET components was causing the K2 to think the AGC was being activated under certain conditions.

I think the oscillation might have been precipitated due to some waxy flux left between the pins of the LM368.

Thank you for your assistance, as always.

> On Dec 7, 2020, at 8:35 PM, Bill Coleman <[hidden email]> wrote:
>
> I’m going to set it up in the damp basement at my other QTH. That’s where I saw the problem originally. Will let you know if it comes back.
>
>> On Dec 7, 2020, at 11:43 AM, Don Wilhelm <[hidden email]> wrote:
>>
>> Bill,
>>
>> It does sound like it is fixed. Just be aware that some intermittents do find their way back, so knowing the symptoms you can recognize it quickly.
>>
>> 73,
>> Don W3FPR
>>
>> On 12/6/2020 6:30 PM, Bill Coleman wrote:
>>> Don,
>>>
>>> I set the K2 up this weekend to try to reproduce this problem. Once again I opened it up and re-installed the K60XV board. I put a scope probe on P1 pin 6.
>>>
>>> I did not see the AGC failure mode right away, but I did find an intermittent oscillation on pin 6 at about 15 MHz. It would come and go, but no AGC activation.
>>>
>>> I removed the board and re-soldered all the components around the LM358. Then I inspected the board and scraped away any residual solder flux in that area of the board between any pins.
>>>
>>> I also re-soldered the 4.0 MHz resonator, although I did not hear or detect any relay activation when it failed before.
>>>
>>> After that, I put the board back in with the scope probe and ran it on the workbench for a day. I saw no AGC failure mode and no more 15 MHz oscillation.
>>>
>>> So, maybe it is fixed? Fingers crossed.
>>>
>>>
>>
>
> Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
> Web: http://boringhamradiopart.blogspot.com
> Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

Don Wilhelm

Re: [K2] Odd AGC problem with K60XV installed

Bill,

I am glad to hear it has not re-occurred. I think your analysis is
correct, except that it would be ALC and power control that would be
affected, not AGC.

73,
Don W3FPR

On 12/16/2020 3:07 PM, Bill Coleman wrote:

> Don,
>
> Just a quick follow-up. I’m going to close the book on this problem, as it has not come up again, despite leaving the K2 on a couple of days.
>
> I think your diagnoses was spot on, I think a 15 MHz oscillation of the K60XV VRFDET components was causing the K2 to think the AGC was being activated under certain conditions.
>
> I think the oscillation might have been precipitated due to some waxy flux left between the pins of the LM368.
>
> Thank you for your assistance, as always.
>
>> On Dec 7, 2020, at 8:35 PM, Bill Coleman <[hidden email]> wrote:
>>
>> I’m going to set it up in the damp basement at my other QTH. That’s where I saw the problem originally. Will let you know if it comes back.
>>
>>> On Dec 7, 2020, at 11:43 AM, Don Wilhelm <[hidden email]> wrote:
>>>
>>> Bill,
>>>
>>> It does sound like it is fixed. Just be aware that some intermittents do find their way back, so knowing the symptoms you can recognize it quickly.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>> On 12/6/2020 6:30 PM, Bill Coleman wrote:
>>>> Don,
>>>>
>>>> I set the K2 up this weekend to try to reproduce this problem. Once again I opened it up and re-installed the K60XV board. I put a scope probe on P1 pin 6.
>>>>
>>>> I did not see the AGC failure mode right away, but I did find an intermittent oscillation on pin 6 at about 15 MHz. It would come and go, but no AGC activation.
>>>>
>>>> I removed the board and re-soldered all the components around the LM358. Then I inspected the board and scraped away any residual solder flux in that area of the board between any pins.
>>>>
>>>> I also re-soldered the 4.0 MHz resonator, although I did not hear or detect any relay activation when it failed before.
>>>>
>>>> After that, I put the board back in with the scope probe and ran it on the workbench for a day. I saw no AGC failure mode and no more 15 MHz oscillation.
>>>>
>>>> So, maybe it is fixed? Fingers crossed.
>>>>
>>>>
>> Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
>> Web: http://boringhamradiopart.blogspot.com
>> Quote: "Not within a thousand years will man ever fly!"
>> -- Wilbur Wright, 1901
>>
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
> Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
> Web: http://boringhamradiopart.blogspot.com
> Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>

Bill Coleman-2

Re: [K2] Odd AGC problem with K60XV installed

Well, it was on receive that the S-meter would pin, and the audio output would be muted, hence AGC….

> On Dec 16, 2020, at 3:19 PM, Don Wilhelm <[hidden email]> wrote:
>
> Bill,
>
> I am glad to hear it has not re-occurred. I think your analysis is correct, except that it would be ALC and power control that would be affected, not AGC.
>
> 73,
> Don W3FPR
>
> On 12/16/2020 3:07 PM, Bill Coleman wrote:
>> Don,
>>
>> Just a quick follow-up. I’m going to close the book on this problem, as it has not come up again, despite leaving the K2 on a couple of days.
>>
>> I think your diagnoses was spot on, I think a 15 MHz oscillation of the K60XV VRFDET components was causing the K2 to think the AGC was being activated under certain conditions.
>>
>> I think the oscillation might have been precipitated due to some waxy flux left between the pins of the LM368.
>>
>> Thank you for your assistance, as always.
>>
>>> On Dec 7, 2020, at 8:35 PM, Bill Coleman <[hidden email]> wrote:
>>>
>>> I’m going to set it up in the damp basement at my other QTH. That’s where I saw the problem originally. Will let you know if it comes back.
>>>
>>>> On Dec 7, 2020, at 11:43 AM, Don Wilhelm <[hidden email]> wrote:
>>>>
>>>> Bill,
>>>>
>>>> It does sound like it is fixed. Just be aware that some intermittents do find their way back, so knowing the symptoms you can recognize it quickly.
>>>>
>>>> 73,
>>>> Don W3FPR
>>>>
>>>> On 12/6/2020 6:30 PM, Bill Coleman wrote:
>>>>> Don,
>>>>>
>>>>> I set the K2 up this weekend to try to reproduce this problem. Once again I opened it up and re-installed the K60XV board. I put a scope probe on P1 pin 6.
>>>>>
>>>>> I did not see the AGC failure mode right away, but I did find an intermittent oscillation on pin 6 at about 15 MHz. It would come and go, but no AGC activation.
>>>>>
>>>>> I removed the board and re-soldered all the components around the LM358. Then I inspected the board and scraped away any residual solder flux in that area of the board between any pins.
>>>>>
>>>>> I also re-soldered the 4.0 MHz resonator, although I did not hear or detect any relay activation when it failed before.
>>>>>
>>>>> After that, I put the board back in with the scope probe and ran it on the workbench for a day. I saw no AGC failure mode and no more 15 MHz oscillation.
>>>>>
>>>>> So, maybe it is fixed? Fingers crossed.
>>>>>
>>>>>
>>> Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
>>> Web: http://boringhamradiopart.blogspot.com
>>> Quote: "Not within a thousand years will man ever fly!"
>>> -- Wilbur Wright, 1901
>>>
>>> ______________________________________________________________
>>> 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
>>> Message delivered to [hidden email]
>> Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
>> Web: http://boringhamradiopart.blogspot.com
>> Quote: "Not within a thousand years will man ever fly!"
>> -- Wilbur Wright, 1901
>>
>