[Elecraft] KIO2/KPA100 Serial Comm Problems

[Steven Pituch]

Hi Tom and All,
I had a similar problem with a non Elecraft I/O device.  I built an I/O 
converter for a TS-850, before I realized how much better the K2 is and 
sold the TS-850 ;o).  It's the standard Kenwood interface using a Maxim 
chip and two opto-isolators.

I added LEDS so I could see activity.  I was not getting any activity 
from the radio to the PC.  I noted that the opto-isolator, when tripped 
by the Maxim voltage going high was taking far too much current.  It was 
pulling the voltage of the Maxim down.  I solved this by putting a 
standard 2n2222 amp between the optoisolator and the Maxim chip.  I made 
sure the 2n2222 did not take so much current from the Maxim to disable 
the output.  This did the trick.

Could it be that your receive rs232 port is drawing to much current from 
the Maxim chip, and pulling the output of the chip down?  In this case a 
2n2222a could boost the voltage to the rs232 port and reduce the current 
used by the Maxim chip.

It should be easy to check the output of the Maxim chip with a DMM. If 
it is being pulled down, try adding the amp.

Regards,
Steve, W2MY

PS I just got my KIO2 working on K2 #402.