[DSP-10] Intermittent PLL Lock Issue

[Bob Larkin]

Hi Rich,

It is possible to measure the tuning voltage at the junction of C111, 
R104 and R105.  For diagnostics, it might be best to pick a midband 
frequency and set the tuning voltage around 3.5 volts. The full tuning 
range is roughly 1 to 5 Volts.

A few hints are at
http://www.proaxis.com/~boblark/dig_pll1.htm

The jumping characteristic would suggest the powdered iron core moving. 
  Be sure it is not out of the metal can.  There can be two tuning 
points and you want the one that is mechanically stable with the core 
far into the can.  You may need to cut/grind the core down in size.

After you are done, don't leave the voltmeter on the tuning voltage, as 
it will AC modulate quite badly!  But this is not a "lock" problem, 
normally, for measuring the voltage.

Let us know how it goes.

73, Bob  W7PUA

On 11/25/2015 05:01 PM, Richard Miller via DSP-10 wrote:
>   All:
> I seem to be having a problem with the PLL. I am able to lock the PLL sometimes, and it will remain locked for a hour or two. Then for no real reason, the PLL will become unlocked. I am able to sometimes get it to relock by adjusting L102 for 127.335MHz when at 147MHz. This is not repeatable, and it does not always lock once again when adjusting L102 for the correct frequency. Once I achieve PLL lock, it will once again run for a few hours, and then come out of lock again.
> Anyone ever seen this issue? If so, what were your findings?
> Rich, AJ3G
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