SB-101 Low SSB Output Problem (ALC?)

[Jim Simmons]

----- Original Message -----
From: "Randall C. Iliff" <riliff at COMMSPEED.NET>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Sunday, March 16, 2003 11:07 PM
Subject: SB-101 Low SSB Output Problem (ALC?)


> 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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> This list is a public service of the City of Tempe, Arizona
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>
Check out
First check the power supply, is it set to 300VDC? If so, then check the
6AU6, make sure it is any brand other than ElMenko (you should get rid of
all El Menkjo tube and as a rule never use them ). Then check the 6146's
make sure that they match, same brand and same type and the are 6146 or
6146A's or W's, no B's. This should get you started in finding out what is
wrong.

Jim, KF4TUN

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