[Elecraft] Re: Need info on K2 bus

[Wayne Burdick]

Burl Borcherding wrote:
> 
> I am putting together my first K2 and the control display test section is
> not working.  I been through the components and connection several times.
> My display show "ELE"and the bar graph has only the 4th bar from the left
> lighted....

Hi Burl,

Sorry to hear of your difficulty. This symptom has only a few possible causes,
and Gary can help you figure it out when he returns. Meanwhile I'll give you
some information that may help.

Chances are that the I-squared-C (I2C) link from the main MCU to the LCD is
working correctly, if any characters are displayed. What's probably happening is
that a control line from the switch-read shift register is floating or shorted
to ground or to a nearby trace, making the MCU think that a front panel button
is pressed. Or you could have a switch shorted to ground. In either case, the
MCU waits indefinitely for the switch to be "released," making the radio
unusable. You can usually find the short by checking resistance to ground from
all of the input shift register pins (74HC165) and then the switch lines. 

Another possibility is that one of the output shift register lines is stuck low,
or that one of the 6B595's has been damaged by ESD. The correct DC levels on all
of the front panel ICs, as measured with a DMM, can be found in Appendix E. If
you haven't checked these, please do. Of course the front panel sheet metal must
first be removed.

73,
Wayne
N6KR


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