[Elecraft] K2 issue

[Don Wilhelm]

Vic,

Troubleshooting rule #1 - Suspect what you touched last, and resist the 
temptation to jump to conclusions.

I would first suspect a voltage drop at the rigrunner (and its fuse) 
rather than a failed PA transistor.  Check the voltage at the K2 end 
under full current load.
Your 2.15 Amps at 10 watts seems about right, so that is not evidence 
enough to declare a bad PA transistor.  I suggest that you remove the 
KAT2 (if installed) and operate the K2 directly into a known good 50 ohm 
dummy load before drawing any other conclusions.   Test with 13.7 to 
13.9 volts at the K2.

You could have a wattmeter anomaly, or if no wattmeter, the load may not 
be exactly 50 ohms.

If after taking those steps you still have less than 12 watts output 
(10w on 10 meters), then it is time to check the RF voltages (with the 
power set to 5 watts) at the Q5 and Q6 collectors. bases of Q7 and Q8, 
and the antenna jack and compare those to the values shown in the 
Transmit Signal Tracing portion of the manual.  If those are correct and 
your maximum power output is still not up to par, then you can suspect 
the PA transistors.

73,
Don W3FPR

Vic K2VCO wrote:
> Tonight I decided to check out my K2, QRP configuration, for Field Day. I tried it on 40, 
> 20 and 15 meters, and it put out a solid 14-15 watts, drawing about 3.5 amp.
>
> Then suddenly it went dark. The fuse in my rigrunner had blown. Silly me, I had plugged 
> the K2 into a slot with a 2 amp fuse. I replaced the fuse with a 5 amp one, and started it 
> up again. But now I can only get about 10w maximum when the power control was turned all 
> the way up! Current draw is now about 2.15 a.
>
> So, did I blow one of my finals? And if so, could the blowing of the external fuse be the 
> cause?
>   
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