[Elecraft] K2 Alignment and Test Part 1

[Cecil Turquette]

Don - Appears problem solved.  Pin 4 of the encoder measured "open" to ground.  I messed around for an hour trying to figure out why.  I finally found the wire from the circuit board to the encoder termal #4 broken.  I used trimmed component leads to make the four connections as called out in the book. Apparently the one on #4 had a nick in it; flexing of the wire during assembly of the front panel caused it to break.  The break was well hidden.  I replaced the wire and encoder functions properly.  Ready to move on! Thanks for your help, 73, Cecil
 
> Date: Thu, 25 Oct 2012 19:37:16 -0400
> From: w3fpr at embarqmail.com
> To: cecilsmail at hotmail.com
> CC: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] K2 Alignment and Test Part 1
> 
> 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. {updated to read "ohms" per Don}
> 
> 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?
> >
>