[Elecraft] K2/100 Extreme high Power Out - What did I do?

[Don Wilhelm]

Bob,

Thanks for answering the configuration/cable questions - that helps a lot.

Since the KAT100 was not connected at the time of the 'incident', it is 
probably just fine.  That is a good assumption for the time being, but 
should be checked out later.

The reason the ICOM R75 would not connect with the cable plugging you 
had is that the cable to the KAT100 does not have the 3 RS-232 signals 
(RXD, TXD and Signal GND) installed on that part of the cable.

It is probable that the ICOM R75 has a 'loopback' connection between the 
normal RTS and CTS signals (pins 7 and 8), so when you left the cable 
(which is normally connected to the KAT100) attached to the ICOM R75, 
and powered the K2/100 the internal 12CTRL line would have applied 12 
volts to the VRFDET signal.
I highly suspect that you zapped U6 in the KPA100 by applying 12 volts 
to its output pin.  You can verify that by looking at the KPA100 
schematic and mentally connecting J8 pins 7 and 8.

However - it is unusual for the condition that when VRFDET is not 
functioning, to have max power out of the KPA100 (120 watts or more) 
*and also* to have no power output when the power is set to less than 10 
watts - normally you would have 120 watts or more if the power control 
was above 10 watts and 12 to 15 watts if the power control is less than 
10 watts.

As a result, I will ask you to physically remove the KPA100 from the 
base K2 and test the power control on the base K2 alone.  If the power 
control is normal (can control between very low power and 12 to 15 
watts), then the base K2 is probably unharmed and the problem is most 
likely U6 of the KPA100.  OTOH, if the base K2 power control is not 
normal, the 'incident' created two failures and we need to tackle them 
one at a time (base K2 first).

My guesses can be wrong, but try the tests that I inferred as first 
order of business and let me know the results.  If the troubleshooting 
get too intense, we will take it off the reflector and you can report 
the final results to the reflector after the problem has been solved.

73,
Don W3FPR

Bob Mallory wrote:
> Thanks Don,
> Your right on target, I was thinking that it was a standard RS232 
> connection, that probably what got me in trouble.
> I have the correctly built I/O cable for use with the K2/100 and a 
> KAT100 to the serial port on my PC.  Has been working with HRD for quite 
> some time.
> I recently acquired a ICOM R75 Receiver and without thinking much about 
> it, unplugged the K2/100 and KAT100 connectors and placed the KAT100 
> connector on to the R75.  This was my 'thoughtless' attempt to use the 
> ICOM R75 with HRD.  It wouldn't communicate.  With no real concern to 
> attempt to troubleshoot, I decided to re-connect the K2/100 to the I/O 
> cable but inadvertently left the R75 connected to what should have been  
> the KAT 100 connector.  Powered on the K2 and had instant smoke.  Smoke 
> wasn't visible but you can't mistake that distinct smell. (took about 10 
> sec to notice)
>
> I powered off, disconnected the R75 and tested the K2 connection to 
> HRD.  Everything seemed to work.
>
> I felt it necessary to pop open the K2 and take a look around the AUX 
> I/O port circuitry and everything 'appeared' ok.  Not until I later 
> attempted to Transmit, did I notice a problem.  Yes, I could have 
> injected a problem when I removed the cover of the K2.
>
> I built the K2/100 and the KAT100 about one year ago and the build went 
> flawlessly.  Now I think my momentary lapse of common sense has caused 
> some problems.
>
> The Tuner will tune the separate bands to give an appropriate SWR but my 
> Watt meter (LP-100A) is showing 147 watts when using the 'Tune' button.  
> It normally only shows approx 17 watts.
>
> I plugged in the Elecraft Dummy load (20 watt) and the Elecraft W1 Power 
> meter and a QRP 'Tune' shows NO Power out.  Turn the Power Dial up to 
> activate the KPA100 and the Wattage immediately jumps to 140+ on the W1 
> watt meter.  Obviously the 20Watt Dummy Load is not happy with that :)
> Bob KD8HXT
>   
>