[Elecraft] KPA 100 - KIO2 not working...

[James T. "Jim" Rogers]

Rein wrote:
"On the TX side, Pin 5 of U4 (TXD) is +12.8 V instead of the -22 mentioned
in
the voltage table. I checked with an ohmmeter, and it looks like this
voltage
must come out of U4. Is the voltage table wrong?"

RS232 specifications are +12v to -12v more or less. If the voltage chart
indicates measuring from 1 pin on the DB9 to signal ground should measure
22v, then yes, it is wrong. Looking at the schematic 0V on pin 12 of U4
would result in +12v out on pin
5 of U4. Everything normal there.

Now we need to figure the quiescent state of the MCU. In order to produce a
"MARK" hold (-12v on pin 5 of U4) the MCU should have +5V on the TXD line.
1) Make sure the PORT is on
2) Make sure your terminal and the K2 are talking and recieving on the
appropriate signal lines. The K2 cable is a straight through cable, no pin
transistions. Your terminal must be "listening" for the K2 on its DB9 pin 2.
The K2 is "listening" for the terminal on its DB9 pin 3(the terminal must be
sending data on its DB9 pin 3).
3) At 4800 baud it doesn't take long for the TEST message to get across the
wire. A DVM would not show much in the way of "wiggles" (mark to space
transitions). You would need a triggered scope to evaluate that.
4) I am certain you have checked for solder bridges, something that would
hold the K2's TXD line low (0V).

I hope this helps with the KI02 problems.

73s Jim W4ATK
K2 #4028 KPA100 not yet installed.