[Elecraft] K2/100 power problem

[Ron D'Eau Claire]

I'd suspect the diodes in the output SWR bridge, Bill. 

The K2 power control works by "requesting" the desired power by turning the
POWER knob and then it ramps up the gain until the output SWR bridge reports
the requested power. 

With then inop the K2 ramps up full power trying to get a power level back
that won't happen if they are dead.

Don Wilhelm, W3FPR, is the resident K2 expert, having built and repaired
countless K2s over the past dozen years or so. I suspect he'll jump in when
he notes your message. But, if not, pulling one end of each diode loose and
checking it for proper diode operation is likely  to show one or both are no
longer "diodes" ;-)

73 Ron AC7AC

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bill and Gail Stewart
Sent: Sunday, March 24, 2013 4:09 PM
To: elecraft at mailman.qth.net
Subject: [Elecraft] K2/100 power problem

I am trying to repair a K2/100 that I believe was damaged in shipment to me.
The power output was erratic - sometimes almost no power out, sometimes
about half power. I investigated the SWR circuitry in the
KPA100 and replaced R29, which was discolored but still had the correct
resistance. After carefully reassembling the unit, the power output is now
greater than maximum rated power regardless of the power setting (just keyed
momentarily and measured with a peak-reading wattmeter).  
The resistance from either side of R28 to ground is about 92 ohms, the same
for the cathodes of D16 and D17. Is this correct? Is U5 blown?

Thanks,

Bill K5EMI
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html