[Elecraft] K3 button problem question

[Paul Ferguson]

Thanks to Harry, WE1X, for letting me know of a similar button problem he had. 
It is most likely my problem is not caused by the components I suspected, but 
rather by the failure of the switch inside the encoder for Speed/Mic. 

I was thinking only of the rubber-covered buttons, which cannot result in a 
ground out. However the four encoders containing push switches can fail by 
putting a ground out to a scan line. There were a few failures on early 
encoders, and Elecraft now uses encoders from a different source. I sent my 
front panel board back for repair.

73,
Paul
K5ESW


> Seven of my front panel buttons do not function on K3 #757. I also used the 
> Switch Test to see that they give no scan codes. All other buttons work OK.
> 
> Looking at the the schematic for the "Front Panel - Switches" I see these
> seven 
> buttons are all connected to the SCANADC0 line into U3. I took off the front
> panel and put an ohmmeter from ground to the SCANADC0 line, and it gives a few
> ohms. The other lines (SCANADC1-7) show as open.
> 
> I looks like either U3, C30, or R27 is bad. Does anyone see any other 
> possibilities?
> 
> I don't relish replacing U3 since it is a 16-pin IC. Maybe some Chip-Quik or
> tiny cutters to snip the leads would ease the job.
> 
> 73,
> Paul
> K5ESW