Re: KX1 build issue after Part 1 of build

Posted by Rod on May 05, 2016; 5:57pm
URL: http://elecraft.85.s1.nabble.com/KX1-build-issue-after-Part-1-of-build-tp7616877p7617192.html

I was just reading about this problem and I have a suggestion.

The PIC micro is used to multiplex the LED display as well as read
the encoder and battery voltage. I don't have access to the code but it probably
goes something like this.

1) Send data to LED0
2) Read the encoder
3) Send data to LED1
4) Read the encoder
5) Send data to LED2
6) Read the encoder
repeat 1 -6

The battery might also be in this loop - it doesn't really matter. If you execute this loop
very fast, the display will not "appear" to flicker. However, if you want, say 3 ma per segment,
you must drive it to 9 ma since the time spent on each LED is 1/3 of the scan time.

If the pic stops "scanning", the LED current will be three times as much. Either the micro
is going off and executing code where it shouldn't or the clock for the micro is stopping.
I would look carefully at the 3.995 MHz crystal. Perhaps "bumping" C24 or C25 with another cap
might get it going once it has stopped. Many times, simply measuring it will start or stop it.

Do you have a scope?

72

Rod