SB-301

[Schichler, Alfred]

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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