[Elecraft] K2 - No SSB Output (long)

[COLIN WHITMORE]

Yeah, K2 #2833 is fully functional, well almost. =20
 =20
When I switch to either of the SSB TX modes I get very little, or no, def=
lection on my antenna tuner's watt meter. I have checked with a fellow ha=
m a few miles away and he indicates that my SSB TX signal is barely audib=
le. It works great on CW and seems to work well on SSB RX. I've listed so=
me test data below.
 =20
Test Data:
 =20
Mic: Elecraft MH-2 w/ supplied resistor installed across P1 & P6
KSB2 U1 v1.07
 =20
Output (DISPLAY mode):
0.1W; 0.26A RX, 0.68A TX(CW), 0.46A TX(SSB) (PTT pushed), 0.56A TX(SSB) (=
Whistling)
10.0W; 0.26A RX, 2.72A TX(CW), 0.46A TX(SSB) (PTT pushed), 0.56A TX(SSB) =
(Whistling)
Note: This was on 20M into 300W dummy load. Similar results on other band=
s.
 =20
DC Voltage Checks: (I've only included the ones that were NOT on target.)=
 Settings per KSB2 manual.
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IC-Pin - RX(V)/TX(V) (Tabulated Values)
 =20
U1-2   - 6.0/6.0     (6.0/5.3-5.9)
U1-6   - 5.7/0.0     (5.1/0.0)
U1-21 - 5.7/0.06    (5.8/0.1)
U1-25 - 0.0/0.7     (0.0/0.8-1.2)
 =20
U4-6   - 5.7/0.0     (5.1/0.0)

Diodes - CW/SSB (table)

D6 - 3.8/5.7 (4.0/6.0)
D7 - 4.4/1.4 (4.6/1.4)
D8 - 4.4/1.4 (4.6/1.4)
D9 - 3.8/5.7 (4.0/6.0)
D10 - 5.1/5.7 (5.4/6.0)
D11 - 5.7/0.0 (5.4/0.0)
D12 - 5.7/0.0 (6.0/0.0)
D13 - 5.1/5.7 (5.4/6.0)
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Transistor(V)  E (RX/TX)  B (RX/TX)  C (RX/TX)
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Q1 - CW:       5.97/5.97  0.00/0.54  5.98/5.98
       SSB:      5.97/0.49  0.00/0.62  5.98/5.98
 =20
Q2 - CW:       1.72/2.60  0.00/0.00  1.73/7.60
       SSB:      0.00/4.98  0.00/5.63  0.00/7.57
 =20
Q3 - CW:       1.73/7.60  2.40/3.26  1.72/2.62
       SSB:      0.10/7.60  0.00/0.00  0.00/4.98
 =20
As can be seen above, the DCV values for the IC's and the diodes are only=
 slightly off target. I don't believe these would be enough to cause prob=
lems. =20
 =20
The transistor values I've included are for those needing additional info=
rmation.
 =20
C167 and the two jumpers on the RF board have been removed.
 =20
All components are in place. All soldering looks good. No missing connect=
ions, no cold joints, etc.
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U2-5 (ALC threshold) varies from about 0.49V to 3.98V as the power pot is=
 increased.
 =20
U3-7 indicates about 300mV when whistling loudly into the mic. P1-5 indic=
ates about 40mV as well.
 =20
FL1 is set to OP1 for CW and SSB per manual.
 =20
Have I missed something? Any suggestions?
 =20
Cheers,
Colin
N=D8YGY


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