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

[Rein Couperus]

On Tuesday 09 March 2004 21:47, Don Wilhelm wrote:
> Rein,
>
> I can find nothing in the circuit that could cause inverted signals on the
> RS232 interface lines.  Be certain you have a negative voltage supplied to
> U4 pin 8.  Ideally that voltage should be -12 volts, but anything between
> -5 and -25 volts should be OK.  If the voltage is not sufficiently
> negative, it may cause the RS-232 lines to not swing far enough negative
> for proper switching at the terminal device (computer serial port).
>
There is -22 V on pin 8... should be enough I think.

> A logic low (ground ) on pin 12 of U4 should cause a negative voltage to be
> presented on pin 5 - this is the binary one voltage for RS232 and can range
> from -3 to -25 volts.
> For a binary zero on the RS232 interface, the voltage should be positive +3
> to +25 volts, and a +5 volt level on pin 12 of U4 should cause a positive
> voltage to be present on U4 pin 5.  If this condition is what you have, the
> signals are of the correct polarity.
>
> The voltage doubler diodes D7 and D8 along with C35 and C38 are the 'power
> supply' for the negative voltage while the oscillator Q8 and xtal X1
> provide the AC signal to the diodes.  Check these if the negative voltage
> is not adequate.
>
> 73,
> Don W3FPR
>
> ----- Original Message -----
>
> > Of course I first did the mods on the control board... and I have checked
>
> that
>
> > the signals come through from the MCU to U4 on the KPA100. Only they are
> > wrong!!. I have an RS232 tester, and I can see signals going from the
> > terminal to the rig, and I can see the voltage swinging a bit on the
> > input (MMU), but no reaction... as if the MCU is deaf. I have done
> > everything
>
> the
>
> > manual said several times... Unfortunately I don't own an oscilloscope.
>
> But
>
> > the path from the terminal to the MMU looks o.k., it just doesn't work.
> >
> > The other way (TXD) it's different. When I compare the RS232 monitor
>
> status
>
> > with e.g. my OMNI VI, on the OMNI the LED is RED, on the K2 it's GREEN,
>
> i.e.
>
> > wrong polarity. Also no flicker of the LED or voltage change when I try
> > to send the test message. And nothing on the terminal (works fine with
> > the
>
> OMNI,
>
> > also at the same speed). And yes, of course I made a special cable for
> > the
>
> K2
>
> > according to the manual. The firmware is 2.03d by the way...
> >
> > Rein PA0R

-- 
Rein@Couperus.com or PA0R@EUDXF.ORG
http://www.couperus.com
http://savannah.nongnu.org/projects/tlf