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K2 PLL reference oscillator problems (DAC side!)

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Chris Smith

K2 PLL reference oscillator problems (DAC side!)

Hi,

I've just completed my K2 up to the PLL reference oscillator.

Initially when I assembled it the PLL reference oscillator would not oscillate at all. No reading on internal counter. I popped it on my external Racal counter and still dead. After tracing the problem out I found that the voltage on input to the varactors was pegged at 7.07V which was too high for the oscillation to carry on. I lifted one end of R19 on the output of U6A and the thing oscillates fine isolating this to a control voltage problem.

Next I checked voltages on the thermistor board and input of the opamp. All good. However the input to U6A pin 3 from the LTC1451 DAC is stuck at 4.095V (top end of DAC range by the looks of it) which is forced up by the opamp. Popped U5 DIN on the scope and spun the VFO and it sends the same data word to the DAC every time regardless of VFO position. The CLK and CS lines are doing their thing correctly.

Anyone got any ideas why the control word is the same? VFO reading on display is changing fine.

What can I do to get out of this hole?

Any help appreciated.

Best regards,

Chris M0XTE
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Dave Van Wallaghen-2

Re: K2 PLL reference oscillator problems (DAC side!)

Chris,

I have worked on a few late model K2'S of late with the exact same problem.
The folks in support are currently looking into it to determine the source
of the problem.

My solution was to replace the Control board EEPROM with a known properly
initialized one and everything came back to life. I even discussed this
with Wayne in Dayton. We're looking into whether we have an EEPROM issue or
a possible programming anomaly with the main PIC MCU.

I'm currently on vacation with my wife 8 miles off the coast of Belize. I
have limited WIFI but will continue to check in.

Stay tuned...

73,
Dave, W8FGU
On May 21, 2019 10:28:00 "Chris Smith" <[hidden email]> wrote:

> Hi,
>
> I've just completed my K2 up to the PLL reference oscillator.
>
> Initially when I assembled it the PLL reference oscillator would not
> oscillate at all. No reading on internal counter. I popped it on my
> external Racal counter and still dead. After tracing the problem out I
> found that the voltage on input to the varactors was pegged at 7.07V which
> was too high for the oscillation to carry on. I lifted one end of R19 on
> the output of U6A and the thing oscillates fine isolating this to a control
> voltage problem.
>
> Next I checked voltages on the thermistor board and input of the opamp. All
> good. However the input to U6A pin 3 from the LTC1451 DAC is stuck at
> 4.095V (top end of DAC range by the looks of it) which is forced up by the
> opamp. Popped U5 DIN on the scope and spun the VFO and it sends the same
> data word to the DAC every time regardless of VFO position. The CLK and CS
> lines are doing their thing correctly.
>
> Anyone got any ideas why the control word is the same? VFO reading on
> display is changing fine.
>
> What can I do to get out of this hole?
>
> Any help appreciated.
>
> Best regards,
>
> Chris M0XTE
> ______________________________________________________________
> 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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Chris Smith

Re: K2 PLL reference oscillator problems (DAC side!)

Hi,

Thanks for the reply. Much appreciated.

That’s a bummer. Is there anything I can do here with the current EEPROM? I have a programmer available. I assuming erasing it and letting the K2 reinitialise it a small per earlier steps won’t resolve this?

Based on looking at it from the outside naively, it feels like theres something up with the VCO linearisation as it’s sending the control word on VFO steps but the same data. I’ll get a bus captures if it helps.

Assume that performing the VCO linearisation steps later won’t fix it either?

Hope you enjoy your vacation - sounds nice!

Best regards,

Chris M0XTE

On Tue, 21 May 2019, at 18:11, Dave Van Wallaghen wrote:

> Chris,
>
> I have worked on a few late model K2'S of late with the exact same problem. The folks in support are currently looking into it to determine the source of the problem.
>
> My solution was to replace the Control board EEPROM with a known properly initialized one and everything came back to life. I even discussed this with Wayne in Dayton. We're looking into whether we have an EEPROM issue or a possible programming anomaly with the main PIC MCU.
>
> I'm currently on vacation with my wife 8 miles off the coast of Belize. I have limited WIFI but will continue to check in.
>
> Stay tuned...
>
> 73,
> Dave, W8FGU
>
> On May 21, 2019 10:28:00 "Chris Smith" <[hidden email]> wrote:
>
>> Hi,
>>
>> I've just completed my K2 up to the PLL reference oscillator.
>>
>> Initially when I assembled it the PLL reference oscillator would not oscillate at all. No reading on internal counter. I popped it on my external Racal counter and still dead. After tracing the problem out I found that the voltage on input to the varactors was pegged at 7.07V which was too high for the oscillation to carry on. I lifted one end of R19 on the output of U6A and the thing oscillates fine isolating this to a control voltage problem.
>>
>> Next I checked voltages on the thermistor board and input of the opamp. All good. However the input to U6A pin 3 from the LTC1451 DAC is stuck at 4.095V (top end of DAC range by the looks of it) which is forced up by the opamp. Popped U5 DIN on the scope and spun the VFO and it sends the same data word to the DAC every time regardless of VFO position. The CLK and CS lines are doing their thing correctly.
>>
>> Anyone got any ideas why the control word is the same? VFO reading on display is changing fine.
>>
>> What can I do to get out of this hole?
>>
>> Any help appreciated.
>>
>> Best regards,
>>
>> Chris M0XTE
>> ______________________________________________________________
>> 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
>

Dave Van Wallaghen-2

Re: K2 PLL reference oscillator problems (DAC side!)

You have it right Chris. I believe the initialization of that linearisation
table that is locking it all up and driving the 12 bit DAC to max voltage.
Cal PLL will not work because there is no lock. So it is stuck.

Still need to track down the problem and then I'm thinking we have to come
up with a way to redo the table to something nominal to move forward.

73,
Dave, W8FGU
On May 21, 2019 11:21:32 "Chris Smith" <[hidden email]> wrote:

> Hi,
>
> Thanks for the reply. Much appreciated.
>
> That’s a bummer. Is there anything I can do here with the current EEPROM? I
> have a programmer available. I assuming erasing it and letting the K2
> reinitialise it a small per earlier steps won’t resolve this?
>
> Based on looking at it from the outside naively, it feels like theres
> something up with the VCO linearisation as it’s sending the control word on
> VFO steps but the same data. I’ll get a bus captures if it helps.
>
> Assume that performing the VCO linearisation steps later won’t fix it either?
>
> Hope you enjoy your vacation - sounds nice!
>
> Best regards,
>
> Chris M0XTE
>
> On Tue, 21 May 2019, at 18:11, Dave Van Wallaghen wrote:
>> Chris,
>>
>> I have worked on a few late model K2'S of late with the exact same problem.
>> The folks in support are currently looking into it to determine the source
>> of the problem.
>>
>> My solution was to replace the Control board EEPROM with a known properly
>> initialized one and everything came back to life. I even discussed this
>> with Wayne in Dayton. We're looking into whether we have an EEPROM issue or
>> a possible programming anomaly with the main PIC MCU.
>>
>> I'm currently on vacation with my wife 8 miles off the coast of Belize. I
>> have limited WIFI but will continue to check in.
>>
>> Stay tuned...
>>
>>
>> 73,
>>
>> Dave, W8FGU
>>
>> On May 21, 2019 10:28:00 "Chris Smith" <[hidden email]> wrote:
>>
>>> Hi,
>>>
>>>
>>>
>>> I've just completed my K2 up to the PLL reference oscillator.
>>>
>>>
>>>
>>> Initially when I assembled it the PLL reference oscillator would not
>>> oscillate at all. No reading on internal counter. I popped it on my
>>> external Racal counter and still dead. After tracing the problem out I
>>> found that the voltage on input to the varactors was pegged at 7.07V which
>>> was too high for the oscillation to carry on. I lifted one end of R19 on
>>> the output of U6A and the thing oscillates fine isolating this to a control
>>> voltage problem.
>>>
>>>
>>>
>>> Next I checked voltages on the thermistor board and input of the opamp. All
>>> good. However the input to U6A pin 3 from the LTC1451 DAC is stuck at
>>> 4.095V (top end of DAC range by the looks of it) which is forced up by the
>>> opamp. Popped U5 DIN on the scope and spun the VFO and it sends the same
>>> data word to the DAC every time regardless of VFO position. The CLK and CS
>>> lines are doing their thing correctly.
>>>
>>>
>>>
>>> Anyone got any ideas why the control word is the same? VFO reading on
>>> display is changing fine.
>>>
>>>
>>>
>>> What can I do to get out of this hole?
>>>
>>>
>>>
>>> Any help appreciated.
>>>
>>>
>>>
>>> Best regards,
>>>
>>>
>>>
>>> Chris M0XTE
>>>
>>> ______________________________________________________________
>>>
>>> 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

Don Wilhelm

Re: K2 PLL reference oscillator problems (DAC side!)

In reply to this post by Chris Smith

Chris,

If your kit was shipped between mid-August 2018 and mid-January 2019,
then the most likely problem is that Q19 should be replaced with a new
J310 from Elecraft.

As for the 7.07 volts from U6A pin 1, that is not necessarily the cause
of the problem (Q19 should oscillate even with almost 8 volts from U6
pin 1) - if it does not, then the problem is Q19.

While waiting for a replacement J310 from Elecraft, try putting a small
value capacitor from the source of Q19 to ground - use 10 to 15pF. Then
measure the PLL Reference oscillator range using the counter probe in
TP3 and entering CAL FCTR in the menu. You should have oscillation at
both the low (BAND-) and high (BAND+) and the frequency of the high end
should be near 12100 kHz.

Another potential problem if the voltage on U5 pin 7 (and as a result U6
pin 1) can be that the /DAC2CS input to U5 pin 3 is always at or near
ground - check for that condition, and if present, find the solder
bridge. That signal line should go to ground as you rotate the VFO, but
otherwise should be at 5 volts. You will need an oscilloscope to see
the negative transitions.

73,
Don W3FPR

On 5/21/2019 12:27 PM, Chris Smith wrote:
> Hi,
>
> I've just completed my K2 up to the PLL reference oscillator.
>
> Initially when I assembled it the PLL reference oscillator would not oscillate at all. No reading on internal counter. I popped it on my external Racal counter and still dead. After tracing the problem out I found that the voltage on input to the varactors was pegged at 7.07V which was too high for the oscillation to carry on. I lifted one end of R19 on the output of U6A and the thing oscillates fine isolating this to a control voltage problem.
>
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html

Chris Smith

Re: K2 PLL reference oscillator problems (DAC side!)

Hi,

That makes sense. I assume this is a bootstrap problem then i.e. the J310 has to be oscillating in the default state before the VCO linearisation can run and set up the LUT inside the EEPROM. Making a large assumption there of course as I can't see the source code!

I tried the 10pF trick from another thread that you mentioned before after researching this issue and unfortunately that didn't start the oscillation.

I did some experiments and will complete one more:

Experiment 1 .... Did a hard reset (456+power up) to see if it reset the data. It showed the initialisation info message. FAIL

Experiment 2 .... I just checked the VXO range by pulling R19 and using another bench supply. The thing gives a relatively reliable 3v p-p until the varactor control voltage hits 6.8V then it stalls. Obviously as DAC output eventually ends up at 7.07V it's game over straight up.

Experiment 3 .... If I leave R19 lifted and run the PLL cal it doesn't throw info 232 straight away but appears to hang, probably because there's no control voltage doing anything which is hopeful if it works how I think it does!

Experiment 4 .... (in progress) I'm going to put a J309 in (I don't have any spare J310s I don't think and this is same FET but binned with different Idss) and see if it oscillates across the full range. I will then run PLL cal. If that works then it'll at least clarify first assumption.

I checked /DAC2CS and it does indeed go low during the load operation. The issue is the control data sent to the DAC is the same.

Thanks for your help. Some ideas to try!

Best regards,

Chris

On Tue, 21 May 2019, at 19:05, Don Wilhelm wrote:

> Chris,
>
> If your kit was shipped between mid-August 2018 and mid-January 2019,
> then the most likely problem is that Q19 should be replaced with a new
> J310 from Elecraft.
>
> As for the 7.07 volts from U6A pin 1, that is not necessarily the cause
> of the problem (Q19 should oscillate even with almost 8 volts from U6
> pin 1) - if it does not, then the problem is Q19.
>
> While waiting for a replacement J310 from Elecraft, try putting a small
> value capacitor from the source of Q19 to ground - use 10 to 15pF. Then
> measure the PLL Reference oscillator range using the counter probe in
> TP3 and entering CAL FCTR in the menu. You should have oscillation at
> both the low (BAND-) and high (BAND+) and the frequency of the high end
> should be near 12100 kHz.
>
> Another potential problem if the voltage on U5 pin 7 (and as a result U6
> pin 1) can be that the /DAC2CS input to U5 pin 3 is always at or near
> ground - check for that condition, and if present, find the solder
> bridge. That signal line should go to ground as you rotate the VFO, but
> otherwise should be at 5 volts. You will need an oscilloscope to see
> the negative transitions.
>
> 73,
> Don W3FPR
>
> On 5/21/2019 12:27 PM, Chris Smith wrote:
> > Hi,
> >
> > I've just completed my K2 up to the PLL reference oscillator.
> >
> > Initially when I assembled it the PLL reference oscillator would not oscillate at all. No reading on internal counter. I popped it on my external Racal counter and still dead. After tracing the problem out I found that the voltage on input to the varactors was pegged at 7.07V which was too high for the oscillation to carry on. I lifted one end of R19 on the output of U6A and the thing oscillates fine isolating this to a control voltage problem.
> >
>

Don Wilhelm

Re: K2 PLL reference oscillator problems (DAC side!)

In reply to this post by Chris Smith

Chris,

If it is a EEPROM data problem, then a Master Reset should load it with
default values - hold the 4, 5, and 6 buttons in while turning power on.

I have not found that the EEPROM has been the source of the problem, but
rather Q19.
Q19 should oscillate with anywhere between 0 volts and 8 volts on the
varactors.

Before assuming it is a possible EEPROM problem, add the capacitor I
indicated and see if it works. You should still replace Q19.

To further check the EEPROM and U5 DAC

On 5/21/2019 1:21 PM, Chris Smith wrote:

> Hi,
>
> Thanks for the reply. Much appreciated.
>
> That’s a bummer. Is there anything I can do here with the current EEPROM? I have a programmer available. I assuming erasing it and letting the K2 reinitialise it a small per earlier steps won’t resolve this?
>
> Based on looking at it from the outside naively, it feels like theres something up with the VCO linearisation as it’s sending the control word on VFO steps but the same data. I’ll get a bus captures if it helps.
>
> Assume that performing the VCO linearisation steps later won’t fix it either?
>
> Hope you enjoy your vacation - sounds nice!
>
> Best regards,
>
> Chris M0XTE
>
> On Tue, 21 May 2019, at 18:11, Dave Van Wallaghen wrote:
>> Chris,
>>
>> I have worked on a few late model K2'S of late with the exact same problem. The folks in support are currently looking into it to determine the source of the problem.
>>
>> My solution was to replace the Control board EEPROM with a known properly initialized one and everything came back to life. I even discussed this with Wayne in Dayton. We're looking into whether we have an EEPROM issue or a possible programming anomaly with the main PIC MCU.
>>
>> I'm currently on vacation with my wife 8 miles off the coast of Belize. I have limited WIFI but will continue to check in.
>>
>> Stay tuned...
>>
>> 73,
>> Dave, W8FGU
>>
>> On May 21, 2019 10:28:00 "Chris Smith" <[hidden email]> wrote:
>>
>>> Hi,
>>>
>>> I've just completed my K2 up to the PLL reference oscillator.
>>>
>>> Initially when I assembled it the PLL reference oscillator would not oscillate at all. No reading on internal counter. I popped it on my external Racal counter and still dead. After tracing the problem out I found that the voltage on input to the varactors was pegged at 7.07V which was too high for the oscillation to carry on. I lifted one end of R19 on the output of U6A and the thing oscillates fine isolating this to a control voltage problem.
>>>
>>> Next I checked voltages on the thermistor board and input of the opamp. All good. However the input to U6A pin 3 from the LTC1451 DAC is stuck at 4.095V (top end of DAC range by the looks of it) which is forced up by the opamp. Popped U5 DIN on the scope and spun the VFO and it sends the same data word to the DAC every time regardless of VFO position. The CLK and CS lines are doing their thing correctly.
>>>
>>> Anyone got any ideas why the control word is the same? VFO reading on display is changing fine.
>>>
>>> What can I do to get out of this hole?
>>>
>>> Any help appreciated.
>>>
>>> Best regards,
>>>
>>> Chris M0XTE
>>> ______________________________________________________________
>>> 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
>

Chris Smith

Re: K2 PLL reference oscillator problems (DAC side!)

Hi,

Received replacement J310 and EEPROM today. I will install the J310 this evening and see where it goes, failing that the EEPROM.

Big thanks to Don and Elecraft's excellent support.

Best regards,

Chris M0XTE

On Tue, 21 May 2019, at 23:37, Don Wilhelm wrote:

> Chris,
>
> If it is a EEPROM data problem, then a Master Reset should load it with
> default values - hold the 4, 5, and 6 buttons in while turning power on.
>
> I have not found that the EEPROM has been the source of the problem, but
> rather Q19.
> Q19 should oscillate with anywhere between 0 volts and 8 volts on the
> varactors.
>
> Before assuming it is a possible EEPROM problem, add the capacitor I
> indicated and see if it works. You should still replace Q19.
>
> To further check the EEPROM and U5 DAC
>
> On 5/21/2019 1:21 PM, Chris Smith wrote:
> > Hi,
> >
> > Thanks for the reply. Much appreciated.
> >
> > That’s a bummer. Is there anything I can do here with the current EEPROM? I have a programmer available. I assuming erasing it and letting the K2 reinitialise it a small per earlier steps won’t resolve this?
> >
> > Based on looking at it from the outside naively, it feels like theres something up with the VCO linearisation as it’s sending the control word on VFO steps but the same data. I’ll get a bus captures if it helps.
> >
> > Assume that performing the VCO linearisation steps later won’t fix it either?
> >
> > Hope you enjoy your vacation - sounds nice!
> >
> > Best regards,
> >
> > Chris M0XTE
> >
> > On Tue, 21 May 2019, at 18:11, Dave Van Wallaghen wrote:
> >> Chris,
> >>
> >> I have worked on a few late model K2'S of late with the exact same problem. The folks in support are currently looking into it to determine the source of the problem.
> >>
> >> My solution was to replace the Control board EEPROM with a known properly initialized one and everything came back to life. I even discussed this with Wayne in Dayton. We're looking into whether we have an EEPROM issue or a possible programming anomaly with the main PIC MCU.
> >>
> >> I'm currently on vacation with my wife 8 miles off the coast of Belize. I have limited WIFI but will continue to check in.
> >>
> >> Stay tuned...
> >>
> >> 73,
> >> Dave, W8FGU
> >>
> >> On May 21, 2019 10:28:00 "Chris Smith" <[hidden email]> wrote:
> >>
> >>> Hi,
> >>>
> >>> I've just completed my K2 up to the PLL reference oscillator.
> >>>
> >>> Initially when I assembled it the PLL reference oscillator would not oscillate at all. No reading on internal counter. I popped it on my external Racal counter and still dead. After tracing the problem out I found that the voltage on input to the varactors was pegged at 7.07V which was too high for the oscillation to carry on. I lifted one end of R19 on the output of U6A and the thing oscillates fine isolating this to a control voltage problem.
> >>>
> >>> Next I checked voltages on the thermistor board and input of the opamp. All good. However the input to U6A pin 3 from the LTC1451 DAC is stuck at 4.095V (top end of DAC range by the looks of it) which is forced up by the opamp. Popped U5 DIN on the scope and spun the VFO and it sends the same data word to the DAC every time regardless of VFO position. The CLK and CS lines are doing their thing correctly.
> >>>
> >>> Anyone got any ideas why the control word is the same? VFO reading on display is changing fine.
> >>>
> >>> What can I do to get out of this hole?
> >>>
> >>> Any help appreciated.
> >>>
> >>> Best regards,
> >>>
> >>> Chris M0XTE
> >>> ______________________________________________________________
> >>> 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
> >
>

Chris Smith

Re: K2 PLL reference oscillator problems (DAC side!)

Hi,

I have replaced the J310 and the oscillator now runs over the full voltage range of the DAC. Many thanks. After this, the PLL calibration routine completes successfully. The EEPROM appears to be ok here.

So at a high level the issue appears to be:

1. The J310 or circuit was at fault. Either the J310 device spread is suspect or the circuit is device spread sensitive. Having built a few VXOs over the years some problems are almost inevitable here so it's expected really.
2. The default EEPROM contents without PLL calibration have no calibration data so it's not possible to tune the oscillator down into a running state, not that it'd help potentially based on point 3.
2. The default DAC value of full scale pegs the varactors at full swing resulting in the oscillator not starting.
3. The PLL calibration routine will not run if the oscillator is not running which is fair enough.

Diagnostic steps to positively identify the issue:

1. Reset K2 (456+power up) to clear cal data. This will wedge the DAC at full scale.
2. Hook scope/counter to TP3 (internal counter is fine). If there is a signal here at around 12MHz, then the oscillator works. No further diagnostics required.
3. Lift one end of R19 to disconnect the DAC from the PLL oscillator.
4. Hook bench supply to RP2 pin 2 or 4. Set on 0V. 9v battery with 1k pot across it and DMM on wiper terminal will do if you don't have a bench supply.
5. Sweep bench supply across 0-8V and ensure that there is a signal at TP3 across the entire range.
6. If there isn't replace Q19 (J310) and retry until there is oscillation across the entire range.
7. Reinsert and solder lifted end of R19.
8. Complete PLL calibration.

As a test, I also tried an NOS On Semiconductor J310 (which arrived the same time as Elecraft's replacement!) and that worked consistently across the board. I have however substituted the Elecraft supplied replacement which matches the On Semi one now as well.

Thanks to Don for landing on this issue straight away. Next steps in progress now.

Best regards,

Chris M0XTE

On Tue, 28 May 2019, at 11:22, Chris Smith wrote:

> Hi,
>
> Received replacement J310 and EEPROM today. I will install the J310 this evening and see where it goes, failing that the EEPROM.
>
> Big thanks to Don and Elecraft's excellent support.
>
> Best regards,
>
> Chris M0XTE
>
> On Tue, 21 May 2019, at 23:37, Don Wilhelm wrote:
> > Chris,
> >
> > If it is a EEPROM data problem, then a Master Reset should load it with
> > default values - hold the 4, 5, and 6 buttons in while turning power on.
> >
> > I have not found that the EEPROM has been the source of the problem, but
> > rather Q19.
> > Q19 should oscillate with anywhere between 0 volts and 8 volts on the
> > varactors.
> >
> > Before assuming it is a possible EEPROM problem, add the capacitor I
> > indicated and see if it works. You should still replace Q19.
> >
> > To further check the EEPROM and U5 DAC
> >
> > On 5/21/2019 1:21 PM, Chris Smith wrote:
> > > Hi,
> > >
> > > Thanks for the reply. Much appreciated.
> > >
> > > That’s a bummer. Is there anything I can do here with the current EEPROM? I have a programmer available. I assuming erasing it and letting the K2 reinitialise it a small per earlier steps won’t resolve this?
> > >
> > > Based on looking at it from the outside naively, it feels like theres something up with the VCO linearisation as it’s sending the control word on VFO steps but the same data. I’ll get a bus captures if it helps.
> > >
> > > Assume that performing the VCO linearisation steps later won’t fix it either?
> > >
> > > Hope you enjoy your vacation - sounds nice!
> > >
> > > Best regards,
> > >
> > > Chris M0XTE
> > >
> > > On Tue, 21 May 2019, at 18:11, Dave Van Wallaghen wrote:
> > >> Chris,
> > >>
> > >> I have worked on a few late model K2'S of late with the exact same problem. The folks in support are currently looking into it to determine the source of the problem.
> > >>
> > >> My solution was to replace the Control board EEPROM with a known properly initialized one and everything came back to life. I even discussed this with Wayne in Dayton. We're looking into whether we have an EEPROM issue or a possible programming anomaly with the main PIC MCU.
> > >>
> > >> I'm currently on vacation with my wife 8 miles off the coast of Belize. I have limited WIFI but will continue to check in.
> > >>
> > >> Stay tuned...
> > >>
> > >> 73,
> > >> Dave, W8FGU
> > >>
> > >> On May 21, 2019 10:28:00 "Chris Smith" <[hidden email]> wrote:
> > >>
> > >>> Hi,
> > >>>
> > >>> I've just completed my K2 up to the PLL reference oscillator.
> > >>>
> > >>> Initially when I assembled it the PLL reference oscillator would not oscillate at all. No reading on internal counter. I popped it on my external Racal counter and still dead. After tracing the problem out I found that the voltage on input to the varactors was pegged at 7.07V which was too high for the oscillation to carry on. I lifted one end of R19 on the output of U6A and the thing oscillates fine isolating this to a control voltage problem.
> > >>>
> > >>> Next I checked voltages on the thermistor board and input of the opamp. All good. However the input to U6A pin 3 from the LTC1451 DAC is stuck at 4.095V (top end of DAC range by the looks of it) which is forced up by the opamp. Popped U5 DIN on the scope and spun the VFO and it sends the same data word to the DAC every time regardless of VFO position. The CLK and CS lines are doing their thing correctly.
> > >>>
> > >>> Anyone got any ideas why the control word is the same? VFO reading on display is changing fine.
> > >>>
> > >>> What can I do to get out of this hole?
> > >>>
> > >>> Any help appreciated.
> > >>>
> > >>> Best regards,
> > >>>
> > >>> Chris M0XTE
> > >>> ______________________________________________________________
> > >>> Elecraft mailing list
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> > >>> Help: http://mailman.qth.net/mmfaq.htm
> > >>> Post: mailto:[hidden email]
> > >>>
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> > >>
> > > ______________________________________________________________
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> > >
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> > >
> >
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Don Wilhelm

Re: K2 PLL reference oscillator problems (DAC side!)

Chris and all,

Let me try to add some clarity to this J310 situation:

1. Thru-hole J310s have been discontinued. Last August, Elecraft
ordered a new supply (from a new source) which proved to be inadequate
for the K2 PLL Reference Oscillator circuit. A source of New Old Stock
for J310s was sought and finally found. Those parts were received in
January 2019 and the stock that was deficient was scrapped.
2. So the K2s which were affected were shipped between mid-August 2018
and January 2019.
Not all J310s shipped during that period were sub-par, some worked fine
while others did not.

3. So this problem reared its ugly head on some of the K2s shipped
during that period while others worked fine.

The problem would show up during the PLL Reference Range Test during
early testing of the K2. Many have been corrected so far, actually I
hope all those which failed have now been corrected - time will tell.
With the current stock of J310s at Elecraft, this problem has been
solved. Warranty support for those K2s exhibiting the problem will be
addressed as the symptoms are revealed.

The circuit is not to blame. The circuit has been unchanged since the
Field Test K3s and it has worked successfully until this J310 situation
came up.

There are no new thru-hole J310s being manufactured from the original
manufacturers - SMD J310s have no problems.

73,
Don W3FPR

On 5/29/2019 4:56 AM, Chris Smith wrote:
> Hi,
>
> I have replaced the J310 and the oscillator now runs over the full voltage range of the DAC. Many thanks. After this, the PLL calibration routine completes successfully. The EEPROM appears to be ok here.
>
> So at a high level the issue appears to be:
>
> 1. The J310 or circuit was at fault. Either the J310 device spread is suspect or the circuit is device spread sensitive. Having built a few VXOs over the years some problems are almost inevitable here so it's expected really.
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Chris Smith

Re: K2 PLL reference oscillator problems (DAC side!)

Thanks for the detailed reply. That makes sense entirely.

To note this K2 shipped in early May so there may be problems still.

Best regards,

Chris M0XTE

On Wed, 29 May 2019, at 14:49, Don Wilhelm wrote:

> Chris and all,
>
> Let me try to add some clarity to this J310 situation:
>
> 1. Thru-hole J310s have been discontinued. Last August, Elecraft
> ordered a new supply (from a new source) which proved to be inadequate
> for the K2 PLL Reference Oscillator circuit. A source of New Old Stock
> for J310s was sought and finally found. Those parts were received in
> January 2019 and the stock that was deficient was scrapped.
> 2. So the K2s which were affected were shipped between mid-August 2018
> and January 2019.
> Not all J310s shipped during that period were sub-par, some worked fine
> while others did not.
>
> 3. So this problem reared its ugly head on some of the K2s shipped
> during that period while others worked fine.
>
> The problem would show up during the PLL Reference Range Test during
> early testing of the K2. Many have been corrected so far, actually I
> hope all those which failed have now been corrected - time will tell.
> With the current stock of J310s at Elecraft, this problem has been
> solved. Warranty support for those K2s exhibiting the problem will be
> addressed as the symptoms are revealed.
>
> The circuit is not to blame. The circuit has been unchanged since the
> Field Test K3s and it has worked successfully until this J310 situation
> came up.
>
> There are no new thru-hole J310s being manufactured from the original
> manufacturers - SMD J310s have no problems.
>
> 73,
> Don W3FPR
>
> On 5/29/2019 4:56 AM, Chris Smith wrote:
> > Hi,
> >
> > I have replaced the J310 and the oscillator now runs over the full voltage range of the DAC. Many thanks. After this, the PLL calibration routine completes successfully. The EEPROM appears to be ok here.
> >
> > So at a high level the issue appears to be:
> >
> > 1. The J310 or circuit was at fault. Either the J310 device spread is suspect or the circuit is device spread sensitive. Having built a few VXOs over the years some problems are almost inevitable here so it's expected really.
>

Don Wilhelm

Re: K2 PLL reference oscillator problems (DAC side!)

Chris,

I would believe that the RF Board components were packed before
mid-January and was not purged of the J310s prior to shipping.
Granted, that should have been purged, but for some reason (perhaps
human error), it apparently was not.

73,
Don W3FPR

On 5/29/2019 10:14 AM, Chris Smith wrote:

> Thanks for the detailed reply. That makes sense entirely.
>
> To note this K2 shipped in early May so there may be problems still.
>
> Best regards,
>
> Chris M0XTE
>
> On Wed, 29 May 2019, at 14:49, Don Wilhelm wrote:
>> Chris and all,
>>
>> Let me try to add some clarity to this J310 situation:
>>
>> 1. Thru-hole J310s have been discontinued. Last August, Elecraft
>> ordered a new supply (from a new source) which proved to be inadequate
>> for the K2 PLL Reference Oscillator circuit. A source of New Old Stock
>> for J310s was sought and finally found. Those parts were received in
>> January 2019 and the stock that was deficient was scrapped.
>> 2. So the K2s which were affected were shipped between mid-August 2018
>> and January 2019.
>> Not all J310s shipped during that period were sub-par, some worked fine
>> while others did not.
>>
>> 3. So this problem reared its ugly head on some of the K2s shipped
>> during that period while others worked fine.
>>
>> The problem would show up during the PLL Reference Range Test during
>> early testing of the K2. Many have been corrected so far, actually I
>> hope all those which failed have now been corrected - time will tell.
>> With the current stock of J310s at Elecraft, this problem has been
>> solved. Warranty support for those K2s exhibiting the problem will be
>> addressed as the symptoms are revealed.
>>
>> The circuit is not to blame. The circuit has been unchanged since the
>> Field Test K3s and it has worked successfully until this J310 situation
>> came up.
>>
>> There are no new thru-hole J310s being manufactured from the original
>> manufacturers - SMD J310s have no problems.
>>
>> 73,
>> Don W3FPR
>>
>> On 5/29/2019 4:56 AM, Chris Smith wrote:
>> > Hi,
>> >
>> > I have replaced the J310 and the oscillator now runs over the full
>> voltage range of the DAC. Many thanks. After this, the PLL
>> calibration routine completes successfully. The EEPROM appears to be
>> ok here.
>> >
>> > So at a high level the issue appears to be:
>> >
>> > 1. The J310 or circuit was at fault. Either the J310 device spread
>> is suspect or the circuit is device spread sensitive. Having built a
>> few VXOs over the years some problems are almost inevitable here so
>> it's expected really.
>>
>

Ryan

Re: K2 PLL reference oscillator problems (DAC side!)

In reply to this post by Don Wilhelm

My K2 was having this same issue with the PLL test. I replaced the Q19 J310
with one on hand and it fixed it. Should I replace all the J310 in my kit,
and option kits, or are the sub-par J310 only a problem in the PLL circuit?

--
Sent from: http://elecraft.365791.n2.nabble.com/
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Don Wilhelm

Re: K2 PLL reference oscillator problems (DAC side!)

Ryan,

Those sub-par J310s should work in all other circuits in the K2.
The only other possible exception is Q18, but if you can successfully
run CAL PLL, then all should be OK at Q18 as well.

The problem J310s at Elecraft was resolved early this year and the
incidences of this problem should be diminishing soon.

73,
Don W3FPR

On 7/7/2019 2:27 PM, Ryan wrote:
> My K2 was having this same issue with the PLL test. I replaced the Q19 J310
> with one on hand and it fixed it. Should I replace all the J310 in my kit,
> and option kits, or are the sub-par J310 only a problem in the PLL circuit?
>
______________________________________________________________
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