[Elecraft] K2 PLL Reference Osc. Range Test failed

[Don Wilhelm]

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:w3fpr at embarqmail.com] 
> Sent: Thursday, June 17, 2010 9:07 AM
> To: Gil Bishop
> Cc: elecraft at mailman.qth.net
> 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  
>>
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>
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