[Elecraft] NG0R - K2 Build/Alignment Issue

[John Hoaglun]

K2 gurus:  

I got a note from Gary (support) and Don (w3fpr) with some ideas.

--I checked the low pass filters and the number of turns.
--I validated that T4 is oriented the right direction
--No burnt relays
--8R/8T are ~8vdc   (R-7.87/T-7.815)
--8R on transmit goes to 0.245vdc
--I clipped W1 to test for PA feedback (no change)
--I removed the bottom panels and cleaned up a couple of joints as a CYA
--Removed and rewound LP for 80m
--Checked & resolder the connections of toroids for 20/30, 15/17, & 40
--Repeaked (on receive) all of the band pass filters with a signal generator
--Repeaked (on transmit) all of the band pass filters

I made some progress:

--Freq-----1 Test----1 Msg----2 Test----2 Msg
 3.750mhz    2.5w    Hi Cur   2.3w      Hi Cur
 7.100mhz    6.1w    Hi Cur   6.6w      Hi Cur
10.100mhz    0.3w    Hi Cur   4.9w      Hi Cur
14.100mhz    0.3w    Hi Cur   5.7w
18.100mhz    9.5w             7.3w   
21.100mhz    4.1w             5.0w
24.900mhz    0.5w             4.9w
28.200mhz    6.0w             6.3w

As you can see I am now getting ~5w on all bands except for 80m. I suspect
that the toroid cleanup might have been part of the answer for 20/30 and
tweaking the band pass brought 10/12 into better alignment.

On the three bands that I get a high current message it appears at the peak
power out and does go away if the power is reduced. Any chance that I am
only seeing power out of Q7 or Q8 instead of both of them? 

Thanks, JH

-----------------------------
John Hoaglun
NG0R - EN25
http://www.hoaglun.com


-----Original Message-----
From: Don Wilhelm

--Snip--

I would definitely say the 20/30 meter low pass filter needs to be checked.
Low power output combined with HI CURR messages normally indicate a low pass
filter problem.

I am not certain how you are getting power output on 10 meters, but not on
12.  That may be a bandpass filter problem.
The low power on 80 may be a bandpass problem too, or it could be a lowpass
filter problem - that lowpass is only used on 80.

--Snip--

Since some of the bands transmit at 6 watts, that may be an indication that
only one of the PA transistors is working.  Do the Hi Curr messages on 40m
cease if you set the power at 5 watts?  If so, suspect one of the PA
transistors is bad.