Low SSB TX power on K2

Posted by N9KO on Jul 05, 2006; 4:48pm
URL: http://elecraft.85.s1.nabble.com/Low-SSB-TX-power-on-K2-tp391810.html

I recently picked up an older K2 # 185.  It's had all the important Elecraft-recommended performance mods and Alerts applied, including the "A to B" upgrade.   The rig works FB on CW.  I am disappointed with the SSB performance, even after using three mikes (and changed mike pin jumpers).  I scanned the email reflector and decided to do voltage checks of the ICs and diodes on the SSB board.   The SSB board is Rev. C. There is no reading on the S-meter when I transmit, and no reading on ALC.   I do get a very weak signal when I used each of the three mikes and listened on my other rig.  I also transmitted PSK and again get a weak signal, however, the IMD was -23.  A couple of hams within 5 miles said they heard me on 20 meter SSB, but just at the noise level.  Another ham who lives about 10 miles away could not hear me, but I heard him calling me.  Firmware is 2.01H and IOC 1.02.  

The following are 'unusual' readings, in that they are more than 2/10's off target or show a reading when the reading should be zero.  

IC/PIN RX(V)-Target RX(V)-Actual     TX(V)-Target     TX(V)-Actual
U1-2             5.9              4.4           5.3-5.9              5.4
U1-6             5.1              5.5             0                      0
U1-9             0.0              0.0            2.3                     1
U1-16             6              6.1              5.4                  3.7
U1-17             6              6.1              5.6                  4.7
U1-21             5.8              5.8          0.1                   0.0
U1-25         0.0                0.0              0.8-1.2              0.6
U1-28         5.6              5.6              2.4                      4.6
U2-1             6              6.1              5.6                      4.7
U2-5             0.6          6                  0.6                      0.4
U2-8             6              6.1              5.4                      3.7
U3-4             1.7          1.3              1.7                      1.3
U3-6             0.0        0.0              0.8-1.2                  0.6
U4-3             0.6              6              0.6                      0.4
U4-6             5.1          5.5              0.0                      0.0


Diode CW(V)-Target     CW(V)-Actual     SSB(V)-Target     SSB(V)-Actual
D10             5.4              5.2                  6                          5.8
D11             6                  5.8                  0.0                      0.1
D12             6                  5.8                  0.0                      0.1


I also did readings on the other diodes on the SSB board, with targets unknown.

D1         ???                  5.6              ???                      5.6
D2         ???                  4.4              ???                      4.4
D3         ???                  1.8              ???                      1.8
D4         ???                  5.8              ???                      5.8
D5          NOT FOUND ON THE BOARD.  
D14         ???                  5.8              ???                      5.8


Can someone provide some direction as to my next step?  My only diagnostic tool, outside of the K2 built-ins, is a DMM.  My background is in accouting and risk management, unfortunately not in eletronics.  

Thanks in advance

Cal
N9KO
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