SB-101 Low SSB Output Problem (ALC?)

[Bill Meara]

Randall:  I recently faced similar problems with an HW-101.  I also use a
D-104, mine with the amp in the base.

Low output all bands USB and LSB.  Only way to get a few watts out required
running it with high levels of ALC action.  Normal output on CW (that was an
important clue -- no ALC on CW).

I decided just to take the ALC circuit out of action.  I found two leads
coming from the diodes that generate the ALC voltage in the PA section.  I
just cut them.  No more ALC. Now I just have to make sure not to overdrive
it. I never liked the ALC anyway.  Reminded me of training wheels.

After I did this, some guys said that they remember a commin ALC problem
with these rigs:  A high value (megohm range) resistor in the ALC circuit
that went high in value over time.  This could have easily caused the ALC
circuit to develop voltages when it should not.

Good luck.   73    Bill  CU2JL
http://planeta.clix.pt/n2cqr

t 10:07 PM 3/16/03 -0600, you wrote:
>Hi All,
>
>First, many thanks to those kind souls who answered my previous SB-101 /
>D-104 mic compatibility inquiry.  What a terrific resource your experience
>represents!
>
>The original problem was (and, unfortunately, still is) very low output on
>either LSB or USB.  CW and Tune positions are fine into a dummy load, but I
>now suspect that the ALC circuitry may be the culprit.  I can get an S-4 to
>S-6 needle kick on voice peaks with the Mic Gain full up, but listening to
>the signal (into a dummy load of course!) using another receiver I find that
>the peaks sound very distorted.  Low level sounds are clearly carried.
>(Indicated power on my Drake MN-4 never exceeds 10 watts on peaks.)  The
>situation is common to all bands, and I see no difference between USB and
>LSB.  Carrier nulls out nicely during adjustment too.
>
>Possibly related is the fact that on receive the S-Meter seems very stingy.
>It zeroes OK, and seems to hold a setting, but it takes a very strong signal
>to hit S-6.  Otherwise, the meter seems to operate normally.
>
>(A quick search of the archives turned up a tantalizing reference from '98
>of a person who had just solved an ALC problem on an SB-102, but alas, the
>original posts weren't found.)
>
>If someone has previously slayed a problem that sounds like this, I'd sure
>appreciate hearing about it!
>
>73's
>
>Randy
>
>(KE0BN)
>
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73 de Bill  CU2JL N2CQR
Sao Miguel Island, Azores, Portugal
900 miles West of Lisbon  37.7N  25.67W
http://planeta.clix.pt/n2cqr

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