[Elecraft] K2 Problem Test Part 1

[Don Wilhelm]

Andy,

Some of the pushbuttons apparently are not working.  The ones you 
mentioned are associated with the /BANK1 signal line on the Front Panel 
Board.  Check front panel U3 very closely for a missed solder 
connection.  U3 also controls the Encoder.  Be certain U3 has been 
oriented correctly (compare with the parts placement diagrams at the 
back of the manual).  The Front Panel pushbutton matrix is decoded by 
Front Panel U2 and U3, so pushbutton problems will likely be associated 
with the wiring of these two ICs.

Front panel U2 should have the 5 volt supply on pin 16 (Vcc).  While 
almost 5 volts will be found at the other inputs, those voltages will 
change when the pushbuttons are depressed - your experience with U2 pin 
5 can be expected.  The voltage will be reduced when a pushbutton is 
held depressed *and* the pushbutton state is queried with the /BANK1 (or 
/BANK2) line from U3.

Check the soldering of the connectors on the Front Panel board, the 
Control Board and the RF Board.  Often an unsoldered connection at these 
connectors is overlooked.

The "problem" that you mentioned with Control Board U2 is not a problem 
at all - I am not certain where you found that U2 pin 5 should be at 5 
volts - it will not go up that high.  You will set U2 pin 5 to 3.8 volts 
later (using R1) when you adjust the AGC Threshold.

73,
Don W3FPR

andy wrote:
> Hello,
>  
> I'm Andy DL 1 XAS building up the K2 with the Nr 6345.
>  
> I built up the control unit, the front panel unit, and the parts from RF
> board. The resistor tests before were succesful.
>  
> Then  the first test on page 43 should be done.
>  
>  
> The test started very good:  the Elecraft and the 7.1000.00 c appears
> correct.
>  
> And the annunciator for the VFO A were turned on. But also the annunciator
> for the PRE turned on. But  the next test tapping the DISPLAY switch didn't
> work(no switching) Also VFO knob and Band switch or Rate switch didn't work.
>  
> So I checked all the units for correct soldering and parts, I didn't find a
> mistake.
>  
> Then I checked the voltage from U2 on Front panel board, and I saw that at
> PIN 5 there were no 5 Volts, which should be there. But when I pressed the
> BAND down switch the voltage went to 4 Volts. I bought a new 74HC165N and
> changed it, but nothing changed. Mistake must be at another point.
>  
> I also checked the U2 on control unit, and there I found out, that instead
> of 6.9 V there only were between 2 and 4 Volt, depending changing the R1
> trimmer.(The reason for the band switches don't work?)
>  
> But the voltage from  U4 (8V) and U5 (5V)  were okay.
>  
> so, I would be very glad, if anyone can help me for finding the problem, so
> that i can go on building my K2  :-)
>  
> 73 from the region of Hamburg
>  
> Andy, DL 1 XAS
>
>
>