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K2 PLL Reference Osc. Range Test failed

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Gil Bishop

K2 PLL Reference Osc. Range Test failed

Hi all,
Just finished part II of the RF board assembly. (If it makes any
difference, this is a ~6-year old never opened kit that I'm assembling, ser
#5441, with the thermistor board mod and the PLL stability mod on the bottom
of the board). PLL reference OSC stable at 12084.34Khz when in CAL FCTR
mode and probe at TP3. But no deviation at all when using BAND+/- to check
range. Haven't started to dive in yet - that's for tonight. Would
appreciate suggestions on how/where to logically start troubleshooting this.

73 and thanks!
Gil ab1jv

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Don Wilhelm-4

Re: K2 PLL Reference Osc. Range Test failed

Gil,

Your troubleshooting should start in the middle. Monitor the voltage at
RF board U5 pin 7 while in the CAL FCTR menu. You should see 4 volts
there when you tap BAND+ and zero volts when you tap BAND-. If that
does not happen, your problem will be found bact toward the
microprocessor, but if the voltages are as expected, your problem lies
in the forward direction, perhaps on the Thermistor board.

Next check is at RF Board U6 pin 1. That should go to 8 volts when
BAND+ is tapped and to near zero with BAND-. If that check fails, look
for the problem on the thermistor board - usually a solder bridge - you
can reach the back of the board if you remove the control board and
front panel.
If the test is OK, then move forward - check the soldering of R19, RP3
and D16 and D17, then monitor the voltage at RP3 pin 1 while doing the
BAND button taps , repeat at RP3 pin 3. If you have a change from 8
volts to zero volts there, all should work - check the frequency at TP3
when tapping the BAND buttons.

Report your progress (or lack thereof). Tell us where it works and
where it does not.

73,
Don W3FPR

Gil Bishop wrote:

> Hi all,
> Just finished part II of the RF board assembly. (If it makes any
> difference, this is a ~6-year old never opened kit that I'm assembling, ser
> #5441, with the thermistor board mod and the PLL stability mod on the bottom
> of the board). PLL reference OSC stable at 12084.34Khz when in CAL FCTR
> mode and probe at TP3. But no deviation at all when using BAND+/- to check
> range. Haven't started to dive in yet - that's for tonight. Would
> appreciate suggestions on how/where to logically start troubleshooting this.
>
> 73 and thanks!
> Gil ab1jv
>
> ______________________________________________________________
> 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

Gil Bishop

Re: K2 PLL Reference Osc. Range Test failed

Hi Don and Gary,

Thanks for the quick replies and you both nailed it. U6 pin1 was being
pulled down by a solder bridge on the thermistor board between the lower pad
of the thermistor and left pad of R-D. Strand of solder no more than 1/10th
the thickness of a hair. Even with the magnifier I wasn't entirely sure it
was there, but it vaporized when I hit it with the iron. Now have a nice
13.1Khz differential between the high and low references.
Appreciate the help. I'm sure I'll be back for more!

73 de Gil
Ab1jv

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Thursday, June 17, 2010 9:07 AM
To: Gil Bishop
Cc: [hidden email]
Subject: Re: [Elecraft] K2 PLL Reference Osc. Range Test failed

Gil,

Your troubleshooting should start in the middle. Monitor the voltage at
RF board U5 pin 7 while in the CAL FCTR menu. You should see 4 volts
there when you tap BAND+ and zero volts when you tap BAND-. If that
does not happen, your problem will be found bact toward the
microprocessor, but if the voltages are as expected, your problem lies
in the forward direction, perhaps on the Thermistor board.

Next check is at RF Board U6 pin 1. That should go to 8 volts when
BAND+ is tapped and to near zero with BAND-. If that check fails, look
for the problem on the thermistor board - usually a solder bridge - you
can reach the back of the board if you remove the control board and
front panel.
If the test is OK, then move forward - check the soldering of R19, RP3
and D16 and D17, then monitor the voltage at RP3 pin 1 while doing the
BAND button taps , repeat at RP3 pin 3. If you have a change from 8
volts to zero volts there, all should work - check the frequency at TP3
when tapping the BAND buttons.

Report your progress (or lack thereof). Tell us where it works and
where it does not.

73,
Don W3FPR

Gil Bishop wrote:
> Hi all,
> Just finished part II of the RF board assembly. (If it makes any
> difference, this is a ~6-year old never opened kit that I'm assembling,
ser
> #5441, with the thermistor board mod and the PLL stability mod on the
bottom
> of the board). PLL reference OSC stable at 12084.34Khz when in CAL FCTR
> mode and probe at TP3. But no deviation at all when using BAND+/- to
check
> range. Haven't started to dive in yet - that's for tonight. Would
> appreciate suggestions on how/where to logically start troubleshooting
this.

>
> 73 and thanks!
> Gil ab1jv
>
> ______________________________________________________________
> 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-4

Re: K2 PLL Reference Osc. Range Test failed

Gil,

Great to hear you found it.

73,
Don W3FPR

Gil Bishop wrote:

> Hi Don and Gary,
>
> Thanks for the quick replies and you both nailed it. U6 pin1 was being
> pulled down by a solder bridge on the thermistor board between the lower pad
> of the thermistor and left pad of R-D. Strand of solder no more than 1/10th
> the thickness of a hair. Even with the magnifier I wasn't entirely sure it
> was there, but it vaporized when I hit it with the iron. Now have a nice
> 13.1Khz differential between the high and low references.
> Appreciate the help. I'm sure I'll be back for more!
>
> 73 de Gil
> Ab1jv
>
> -----Original Message-----
> From: Don Wilhelm [mailto:[hidden email]]
> Sent: Thursday, June 17, 2010 9:07 AM
> To: Gil Bishop
> Cc: [hidden email]
> Subject: Re: [Elecraft] K2 PLL Reference Osc. Range Test failed
>
> Gil,
>
> Your troubleshooting should start in the middle. Monitor the voltage at
> RF board U5 pin 7 while in the CAL FCTR menu. You should see 4 volts
> there when you tap BAND+ and zero volts when you tap BAND-. If that
> does not happen, your problem will be found bact toward the
> microprocessor, but if the voltages are as expected, your problem lies
> in the forward direction, perhaps on the Thermistor board.
>
> Next check is at RF Board U6 pin 1. That should go to 8 volts when
> BAND+ is tapped and to near zero with BAND-. If that check fails, look
> for the problem on the thermistor board - usually a solder bridge - you
> can reach the back of the board if you remove the control board and
> front panel.
> If the test is OK, then move forward - check the soldering of R19, RP3
> and D16 and D17, then monitor the voltage at RP3 pin 1 while doing the
> BAND button taps , repeat at RP3 pin 3. If you have a change from 8
> volts to zero volts there, all should work - check the frequency at TP3
> when tapping the BAND buttons.
>
> Report your progress (or lack thereof). Tell us where it works and
> where it does not.
>
> 73,
> Don W3FPR
>
> Gil Bishop wrote:
>
>> Hi all,
>> Just finished part II of the RF board assembly. (If it makes any
>> difference, this is a ~6-year old never opened kit that I'm assembling,
>>
> ser
>
>> #5441, with the thermistor board mod and the PLL stability mod on the
>>
> bottom
>
>> of the board). PLL reference OSC stable at 12084.34Khz when in CAL FCTR
>> mode and probe at TP3. But no deviation at all when using BAND+/- to
>>
> check
>
>> range. Haven't started to dive in yet - that's for tonight. Would
>> appreciate suggestions on how/where to logically start troubleshooting
>>
> this.
>
>> 73 and thanks!
>> Gil ab1jv
>>
>> ______________________________________________________________
>> 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
>
>