[TenTec] Argonaut 505 9 volt regulated spply

[JOHNNY BABCOCK]

GARTY,
U DA THE MAN!!
JOHNNY

On Sun, Feb 2, 2020 at 4:40 PM Gary Follett <dukeshifi at comcast.net> wrote:

> Looking at the discussion below, would it not be a good idea to replace
> said regulator with a 7809 regulator?
>
> Gary
>
> W0DVN
>
>
> >
> >
> >
> > Greetings:
> >
> > I am working on an Argonaut 505.
> >
> > The 9 MHz BFO is low in frequency,  cannot be pulled in. This resulted
> in severely reduced output power in CW or Tune since the carrier is now out
> of the filter passband.
> >
> > My question is, has anyone actually measured the 9 volt line in one of
> these?
> >
> > The line is nominally tagged as “9 volts”, but all of the test points in
> the manual call out 9.5 volts.
> >
> > This particular radio measures 8.0 volts on this line, too low, in my
> estimation, and this could account for the frequency error in the BFO.
> >
> > The regulator is pretty ingeniously simple and cheap - it actually has
> error measurement via Q8, whose base is established by the difference
> between the supply output voltage and the base of Q8. Q8 then controls the
> pass element, Q7, to hold the “9 volt” line constant.
> >
> > However, it seems to me that a change in the gain of Q8 would affect the
> output voltage…
> >
> > Gary
> >
> > W0DVN
> >
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