[Elecraft] K2 Alignment and Test Part 1

[Don Wilhelm]

Cecil,

I suggest you check the soldering on the front panel board, be 
especially aware that on all ICs pin 1 is soldered, that is easy to miss.
Check the schematic for the front panel board and look at the symbol for 
the encoder.  Measure to make certain you have 5 volts on the 5 volt pin 
(measure at the encoder terminal not the board), then turn power off and 
measure the resistance from the encoder ground terminal and ground - 
expect zero volts.

Having made those measurements, monitor the voltage at the ENC A 
connection while you *slowly* rotate the encoder shaft.  The voltage 
should change from low (about zero volts) to high (about 5 volts) as you 
rotate the shaft.  Make the same check for the ENC B signal line.
If those checks reveal that the voltage is always near zero, the first 
suspect is a damaged input on U3 - that IC is quite sensitive to static 
during the installation process.

I would suggest that the voltage checks on the Front Panel board can be 
misleading if you are not familiar with the K2 - the conditions set up 
prior to measurement must be carefully observed.  You are dealing with 
digital signals which are highly dependent on all the conditions being 
the same as on the unit that was measured for the manual list - if any 
condition is different, the results will be different.

73,
Don W3FPR

On 10/25/2012 7:05 PM, Cecil Turquette wrote:
> In process of building an older K2 kit, SN 3943. I'm at the Part 1 alignment page 42 - the optical encoder test.
>   
> Status:  All ok to this point with display reading 40M 7100.00c and VFO A  However, the indication does not change when turning the VFO knob.  I've verified per the steps in Appendix E 012 on page 2, voltages in step 050 on page 3, and all of step 075 on page 5.  The 4 mhz osc can be heard in my station receiver and will change when I adjust C22 on the control board.
>   
> The next test: the relay test appears to work as the band changes and the display reads out for each band.  But as with the 40M position, the frequency does not change when turning the VFO knob.
>   
> Is there anything I should check before beginning the voltage checks beginning on page 15?
>