[Elecraft] K2 VCO Alignment only 0.02V @ R30

[Don Wilhelm]

Jeremy,

The DC voltages at U4 pins 1 and 2 are suspicious.  The voltage at pin 5 
is from the MCU digital outputs, so I would not be to concerned about it 
just yet.  However, compare the voltage at U4 pin 5 with the voltage at 
U7 pin 2 - that is the same signal, and the voltages should be the 
same.  If they are not, then there is a connection problem.

If the U7 pin 2 and the U4 pin 5 voltages are the same, I would suggest 
a replacement of U4 may be in order - but first check for a solder 
bridge across C87 - that would drag the U4 pins 1 and 2 voltages down to 
close to zero.

73,
Don W3FPR
On 2/2/2013 7:56 PM, JeremyJones wrote:
> C62 is correct, and the path is intact.  Reflowed the solder on all
> connections just to be sure.
> U4 readings are as follows
> Pin1 = 0.111
> Pin2 = 0.339
> Pin3 = 0.006
> Pin4 = 2.363
> Pin5 = 4.99
> Pin6 = 4.99
> Pin7 = 4.99
> Pin8 = 4.99
> Pin9 = 0.001
> Pin10 = 0.001
> Pin11 = 0.000
> Pin12 = 0.000
> Pin13 = 5.029
> Pin14 = 5.029
> Pin15 = 5.029
> Pin16 = 5.029
>
> Pins 1, 2, 7, 8, 12, and 13 are not within the specs in the manual.  Is this
> a bad U4, or should I start tracing backwards?
>
>
>
>
> --
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