[Elecraft] K2/10 Low power

[Don Wilhelm]

Byron,

OK on the DC voltages.  You may have to resort to measuring the RF 
voltages as indicated in Appendix E of the manual - Transmit Signal 
Tracing to find where the failure might be.

Check the value of R98 on the bottom of the RF board.  The fact that the 
maximum power drops off significantly on the higher bands tells me that 
the value of R98 could be greater than the stock value of 270 ohms.

What happens to the voltage at RF Board U9 pin 3 when you do a TUNE?  It 
should drop to 1/2 the value that it has during receive.  If not, Q20 is 
not working properly.

For your 160 meter problem - is C153 68pF?  Also is C68 10pF (if you 
have an older K2, it may be 4.7pF.

On the irregular behavior of the POWER knob, it could be a worn pot - 
look at the power displayed as you turn the knob - it should be smooth. 
If it is, my suspicion lies with the value of R98.  Remember that the 
VALC voltage is what actually controls the drive to the TX Mixer, and 
the value of R98 is a controlling factor in the power control loop damping.
If this K2 had the KPA100 installed and the power output went up and 
down during transmission, the fix is to increase the value of R98 - some 
builders went too far with the increase resulting in low power on the 
higher bands and possibly 160 meters.

73,
Don W3FPR

On 1/19/2017 10:55 AM, Byron Allen wrote:
> Don,
>
> I have now done more tests and bandpass filter alignments....Don,
>  As you suggested I checked all the voltages in the Elecraft manual on the
> RF board. All are good...
>
> Here is the  (MAX) power (OUT) int a dummy load on each band and I noticed
> something  that was peculiar.
>