Hi, A report on recent events with my KX3: When I tried to use it yesterday, I found that several buttons were no longer responding: PRE, ATT, MSG and CLR.
Tried power-off/on, no change. Removed the battaries for 5 minutes, no change. I was able to go to setup and started SW TEST so I could test the front panel. Every button and knob was working, except for these four, which didn't show up with the test. Looking at the K3 schematics, these buttons all share the same SCAN103 going to pin27 of U10 on the front panel, the front panel processor. Briefly, there is a voltage divider (R81, R80, R90, R89, R96) and operating any of the four buttons should switch a different voltage to SCAN103. This clearly worked for SCAN100, SCAN101, SCAN102, SCAN104 but not for SCAN103. I was worried that the SCAN103 input was zapped. Looking for people wo encountered this before, I found the blog from OK1RP (http://ok1rp.blogspot.com/2019/05/no-response-from-msg-pre-and-attn-keys.html). On the blog, the solution was to disconnect the flexfoil PCB between control board and RF board, clean the contacts and re-install. I checked the connectors - they were seated correctly as predicted in the blog, I disconnected them, looked for dirty / corroded connectors, and re-set it, and fortunately the issue was solved. So, if others encounter this, Petr's blog may help. But, I still wonder what had happened. The SCAN103 signal is not connected to said connector and a bad contact cannot affect SCAN103. SCAN103 only connects said buttons and the CPU, and that is all on the control panel - no-where near to the interconnect connectors with the flexfoil. I wonder if an initialisation issue on the frontpanel processor U10 can have caused this? Looking closer at the schematic, I see that the SCAN lines are completely floating if a button isn't pressed. If nu button is pressed, the input represents a high-impedance floating input. A static field (an operator walking to the radi, and, without touching the radio first, opererating one of the buttons) may perhaps cause an issue setting up the input. I wonder why these pins don't have 100k to GND or so? Perhaps the disconnect made power really disappear to do the recovery? I noticed that my KXBC3 clock was running 20 minutes behind after the operation - that is the time I worked on the issue, so just removing the power isn't good enough to really drop all power. I don't want to badmouth Elecraft, and I don't want to start a war similar to the "yaesu IF filter discussion" of a few years back, but I wonder if someone has done a more thorough investigation? I note that adding resistors is easy (add them at the encoders) and wonder if this is a change that has been implemented with newer KX3 builds? Comments? 73, Geert Jan PE1HZG ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
