[Elecraft] [K2] POWER control has no effect on actual transmit power

[David Dietrich]

Along with what Don Wilhelm suggests, I would also look at all the RF board SMT IC's on daughterboards and see if any of the pins on the IC's themselves are not 100% soldered.  I had a similiar problem on my K2, and the problem turned out to be an unsoldered pin.  Once it was soldered, and a connection made, the K2 was up and running.

73,

David
KC9EHQ
K2/10 #7164




________________________________
 From: Ben Byer <bbyer at mm.st>
To: Elecraft at mailman.qth.net 
Sent: Saturday, October 27, 2012 6:44 PM
Subject: [Elecraft] [K2] POWER control has no effect on actual transmit power
 
I've had fun putting together K2 #7373, and am finally at the point of doing the 40-Meter Transmitter Alignment (manual, p.78).   I have the unit connected to a 50-ohm dummy load, and am trying to tune L1 and L2 to show 2W on the internal wattmeter.   When I press TUNE, the measured power ranges from 0.2W-0.4W.

I can adjust the POWER knob to show 0.1W - 15.2W while the unit is idle, so the knob reading circuit works -- but adjusting the knob doesn't change the reported transmit power even slightly (remains 0.2W-0.4W), and neither does adjusting L1 or L2.

I suspect that the measurement is correct, because the overall unit power consumption is measured as 11.9V 0.20A when idle, and 0.42-0.44A when in TUNE mode (regardless of what I set POWER to before enabling TUNE -- same result with 0.1W vs 15.2W)

I already checked the voltages on RF Q5, Q6, Q7, and all seem reasonable.  (Actually, initially I measured 0v on the Q6/Q7 collector during transmit, and discovered that I had swapped two wires on T3.   Fixing that brought the voltage up to almost 12v, but did not change the transmit power).

Any suggestions?

Thanks,
Ben (KJ6ZGJ)

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