[Elecraft] K-2 Part II test and alignment problem

[Larry Wright]

Hi All,

I am at the Alignment and Test Part II.

Minor problems with direct freq entry were resolved by resoldering connections, but having difficulty described below.

PLL Reference Osc Range Test yields 12.099 - 12.086 = 13 Khz range.  But  the VCO Test yields 5.535 Mhz instead of the expected 10 to 12 Mhz reading.

The K-2 receives every 5 Khz .   The problem seems to me to involve the 12 Bit DAC (U5).  Have resoldered the pins to it.    Pin 8 is 5v, but pin  7 stays at 3.4v at all times.  Pin 1 on U6 stays at 7.6v.   (the 8v Regulator output is 7.6v)  The 7.6v output is present to the PLL ref. osc circuit.  Turning the dial has no effect on the output of the DAC.  The PLL Reference osc stays at 12.099 Mhz.    

BFO appears to be working fine.  Sensitivity appears good as I can easily hear a 1 uv signal.

I have thought of putting say, a 5 K resistor across the output of pin 1  (or from the 2.7K R19 to ground) on U6 to change the 7.6v to something lower to see if that changes anything, but not  have not tried that yet.  I'm trying to think of a way to test the 12 Bit DAC to see if it is good.

Any suggestions or help will be greatly appreciated.

Larry
N4QY
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