K3 max power out 63W?

[Rob May-2]

I dont' know when it happened, but I can no longer get full power out of my K3 (s/n 1417 FW 2.58 DSP 1.94).  Using the tune control, power out will not go above 63 watts.  I can do the TXGN calibration at 5W and 50W with no problem.  But if I turn up the power, the output never goes above 63W, i.e. if I dial in 50, I get 50W, if I dial in 63, I get 63W, if I dial in 75, I get 63W, if I dial in 100 or 120, I get 63W.  It used to work ok.  This is all into a dummy load with an indicated SWR of 1.1-1.  What could have happened?  I've tried going back to FW 2.45, but the problem still exists.  Any help would be appreciated.
Rob
NV5E

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[Rob May-2]

I was using the internal wattmeter in the K3.  I don't have an external wattmeter.  I hooked the radio up to an oscilloscope today and the power maxes out between the 60 and 70 watt setting.  The scope is an old Tektronix 422 and the absolute measurements probably aren't that accurate, but the relative measurements should be valid.  Here's what I get:
Setting      Output
10             9
20             16
30             23
40             31
50             46
60             67
70             77
80             77
90             77
100            77
110            77
120            77

The measurements are subject to interpolation of a fuzzy line on a small, old crt on an old 15MHz scope, so I'm not as concerned about the actual numbers as I am the fact that they level off after about 65 watts indicated on the power setting.  The measurements were take on the 160m band into a dummy load with the ATU bypassed and an indicated SWR of 1.1-1.  I'm thinking that one of the finals in the KPA3 has failed.
Rob
NV5E
K3 #1417


From: [hidden email]
To: [hidden email]
Subject: RE: [Elecraft] K3 max power out 63W?
Date: Sun, 2 Nov 2008 07:25:23 -0600



How are you measuring your power output? Are you using an external
wattmeter? If not, you don't know if you have a power problem or a metering
problem.
 
Use an external wattmeter and report your findings. Also, is your
tuner in bypass?
 
Mike
AI4NS



From: [hidden email]
[mailto:[hidden email]] On Behalf Of Rob
May
Sent: Saturday, November 01, 2008 7:29 PM
To:
[hidden email]
Subject: [Elecraft] K3 max power out
63W?


I dont' know when it happened, but I can no longer get full power out
of my K3 (s/n 1417 FW 2.58 DSP 1.94).  Using the tune control, power out
will not go above 63 watts.  I can do the TXGN calibration at 5W and 50W
with no problem.  But if I turn up the power, the output never goes above
63W, i.e. if I dial in 50, I get 50W, if I dial in 63, I get 63W, if I dial in
75, I get 63W, if I dial in 100 or 120, I get 63W.  It used to work
ok.  This is all into a dummy load with an indicated SWR of 1.1-1.  
What could have happened?  I've tried going back to FW 2.45, but the
problem still exists.  Any help would be
appreciated.
Rob
NV5E



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