[Elecraft] K2 PLL Reference Osc. Range Test failed

[Don Wilhelm]

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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