[R-390] 3TF7 Substitutes

[Dallas Lankford]

Uhhh... I guess I need to look at my mod again and try to figure out where
it is invasive.  I must have missed something.  But you can get all my
parts, except the miniature 9 pin tube socket, at Radio Shack.  I think that
outweighs any invasiveness (which I can't seem to find anyway).

Dallas


----- Original Message -----
From: "David Wise" <David_Wise at Phoenix.com>
To: "Cecil Acuff" <chacuff at cableone.net>; <r-390 at mailman.qth.net>
Sent: Friday, September 24, 2004 4:51 PM
Subject: RE: [R-390] 3TF7 Substitutes


> Right.  (I presume you mean "switching regulator circuits", not
> linear.)  By the way I did a linear regulator too.  It worked
> fine but I didn't like the extra stuff cluttering up the view.
>
> I once put a Sangean ATS-803A at maximum gain right next to the
> 3DW7A when it was still a breadboard, and with certain antenna
> orientations I could hear a little bit of hash around 150-300kHz.
> I don't hear any noise in the R-390A itself, at any frequency.
> My circuit uses reverse phase control at 120Hz, which is much
> quieter than anything one can do with the kind of switcher you're
> probably thinking of.  The MOSFET pass elements are on at zero
> cross, and softly turn off part way through the waveform.
>
> I'm not arguing that my circuit is simple, far from it.  Some
> would call it an obsession gone wrong.  But to my knowledge
> it's the only good regulator that is also 100% nonintrusive.
> You don't so much as have to loosen a screw, you just plug
> it in like a 3TF7 and it plays.
>
> 73,
> Dave Wise
>
> > -----Original Message-----
> > From: Cecil Acuff [mailto:chacuff at cableone.net]
> > Sent: Friday, September 24, 2004 2:25 PM
> > To: David Wise; r-390 at mailman.qth.net
> > Subject: Re: [R-390] 3TF7 Substitutes
> >
> >
> > There are any number of complex ways to solve the 3TF7 issue
> > but we should
> > not be short sighted and forget about any noise that might be
> > generated by
> > the solution.  Linear regulator circuits work great but are
> > quite noisy.
> >
> > The new fangled sand box radios suffer from many problems
> > associated with
> > noise generated by devices internal to the radio...fortunately the 390
> > series doesn't have that problem....that's one of the things
> > that makes it
> > such a stand out performer.
> >
> > Cecil...
> > ----- Original Message -----
> > From: "David Wise" <David_Wise at Phoenix.com>
> > To: <r-390 at mailman.qth.net>
> > Sent: Friday, September 24, 2004 3:29 PM
> > Subject: RE: [R-390] 3TF7 Substitutes
> >
> >
> > > -----Original Message-----
> > > From: mikea [mailto:mikea at mikea.ath.cx]
> > > Sent: Friday, September 24, 2004 10:29 AM
> > > To: r-390 at mailman.qth.net
> > > Subject: Re: [R-390] 3TF7 Substitutes
> > > cause of this drift.
> > >
> > > Thanks _very_ much for your research results. I have had the benefit
> > > of your expertise for some years now, and think it is appropriate to
> > > give you your due in public.
> > >
> > > I feel some construction coming on.
> >
> > If you're in the mood for construction and would prefer to make
> > *no modifications whatsoever* to your radio, you might consider
> > the 3DW7A, which I designed a while back.  Thanks again to Roy Morgan
> > for massaging the picture into a portable format.  I tried to post
> > it here, but the listserv rejected the .jpg attachment.  Contact
> > me off-list and I'll email it to you.  The single-source items
> > (the MOSFETs and the RMS converter IC) are available at DigiKey.
> > Everything else is generic.
> >
> > It's a cool-running two-pin module, although you'll
> > need a magnifying glass and tweezers to cram it into
> > the "tubester" form factor like I did.  Maybe I ought to
> > post a photo of the completed unit to prove it can be done.
> >
> > By the way, I'm still working on the 3DW7D, which does the
> > same job digitally at about 1/2 the parts count.  Somebody
> > asked for a LED to simulate the olde-tyme glow, and I got
> > carried away.  Soon (but that means < 5 years :)
> >
> > 73,
> > Dave Wise (SWL)
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> >
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