SB-301

[Mark Graalman WB8JKR]

  Check the value of R104, R103, R109 and R108
any of these resistors would affect the S meter reading.

Mark  WB8JKR


On Mon, 31 Mar 2003 11:50:09 -0500 "Schichler, Alfred"
<ASchichler at MICROWAVEDATA.COM> writes:
> I tried a 6GM6 for V1, and the meter actually reads lower with
> apparent
> lower sensitivity. The tube is brand new.
> I also replaced the 6BA6's in the IF stages. I tried a 6AH6 in the
> second
> IF, and it made a little improvement, but not a lot.
> I also re-aligned the RF and IF stages with a signal generator. The
> sensitivity seem good, but the meter still reads low.
>
> The calibrator signal reads about S3 on 20 meters and about S6 on 40
> meters,
> and almost nothing on 10 meters. Maybe it's possible that the meter
> movement
> has a problem.
>
>
> -----Original Message-----
> From: Stu Lyon [mailto:slyon at pacificnet.net]
> Sent: Monday, March 31, 2003 11:03 AM
> To: Schichler, Alfred; HEATH at LISTSERV.TEMPE.GOV
> Subject: Re: SB-301
>
>
> Al,
> Your SB-301 S-meter reads way too low. Using the calibrator as a
> signal
> source my SB-301 reads as follows:
>
> 3.7 MHz    S9+40
> 7.2 MHz    S9+40
> 14.2 MHz  S9+30
> 21.2 MHZ  S9+20
> 28.2 MHz   S7
>
> I think you have a bad tube (or tubes) in the RF/IF stages or your
> set is
> badly out-of-tune. If you plan to retube, try a 6GM6 in place of the
> 6BZ6 at
> V1. Really makes a difference.
>
>
> 73, Stu W6CUX
> Winnetka, CA
> slyon at pacificnet.net
>
>
> ----- Original Message -----
> From: "Schichler, Alfred" <ASchichler at MICROWAVEDATA.COM>
> To: <HEATH at LISTSERV.TEMPE.GOV>
> Sent: Monday, March 31, 2003 6:13 AM
> Subject: SB-301
>
>
> > I was wondering if it is somewhat normal for  the S-meter on the
> SB-301 to
> > read very low compared to most modern receivers. I think mine has
> always
> > read pretty low, but it seems lower than it used to be. (I have
> owned it
> for
> > about 5 years, but haven't used it for a couple years until
> recently).
> About
> > the highest it ever reads is around S-6, and that is on extremely
> strong
> > signals.
> > I tried experimenting with changing some resistors in the meter
> circuit
> with
> > almost no improvement, and also tried changing a couple of the
> resistors
> in
> > line with the AGC voltage which did make the meter read a little
> higher,
> but
> > it sounded like it was overloading slightly on very strong
> signals. The
> > meter voltage seems to be derived from the second IF tube cathode,
> so I'm
> > not exactly sure how it works, not being an expert on tube theory.
> Maybe
> I'm
> > being a little too fussy, but I would just like to know if it is
> working
> > pretty much the same as most of the SB-301's out there.
> >
> > Thanks for any help,
> > Al, NE2D
> >
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