[R-390] No Peak on T701
Barry
n4buq at knology.net
Sun Apr 30 00:09:55 EDT 2006
Hmmm. It appears the adjustment I *thought* I was making to the transformer
was not the transformer at all, but C706! Although the schematics are drawn
with an arrow through T701 (which I always took to mean an adjustable
(usually slug-tuned) transformer), it appears the transformer in Z702 is
fixed (the windings are on top of each other with no slug tuning).
Now, I'm still wondering what C706 is tuned for. Maximum output? If so,
I'm not seeing any change with it.
Thanks again, guys.
Barry - N4BUQ
----- Original Message -----
From: "Barry" <n4buq at knology.net>
To: <bill at iaxs.net>; "R-390A" <r-390 at mailman.qth.net>
Sent: Saturday, April 29, 2006 10:54 PM
Subject: Re: [R-390] No Peak on T701
> That's a good point; however, why is the transformer slug tuneable? I
> realize that just because a component happens to have an adjustment that's
> not a reason to go about adjusting it (golden screwdriver syndrome), but
it
> would seem they put adjustments on these components for some reason,
right?
> I assumed the output of the oscillator should be maxed somehow, even if it
> is a low-Q circuit.
>
> Although I don't see it in the Y2K file, I do seem to recall seeing
> something about adjusting this in one of my other manuals. I'll have to
> check.
>
> Thanks!
>
> Barry - N4BUQ
>
> ----- Original Message -----
> From: "Bill Hawkins" <bill at iaxs.net>
> To: "R-390A" <r-390 at mailman.qth.net>
> Sent: Saturday, April 29, 2006 10:30 PM
> Subject: RE: [R-390] No Peak on T701
>
>
> > Ah, les'see, the output PTO coil will not peak.
> >
> > Doesn't seem like it would be a good idea for it to peak.
> >
> > The PTO generates 2.5 to 3.5 meggycycles, and they've all got
> > to be mixed with the masticated RF from the RF deck. A sharp
> > peak at 3.0 MC would seem like a very bad idea. If you want a
> > reasonably level signal for 3 +/- 0.5 MC, you want a really
> > low Q circuit.
> >
> > What have I missed?
> >
> > Bill Hawkins
> >
> >
> > -----Original Message-----
> > From: r-390-bounces at mailman.qth.net
> > [mailto:r-390-bounces at mailman.qth.net]On Behalf Of Barry
> > Sent: Saturday, April 29, 2006 10:23 PM
> > To: R-390A
> > Subject: [R-390] No Peak on T701
> >
> >
> > I've been doing some more tweaking on one of my R390As. T701 (output
> > transformer from the PTO) will not peak. I'm getting slightly less then
> 2V
> > peak to peak no matter how I adjust the slug. Anyone ever seen this
> > behavior? If so, any ideas what's wrong?
> >
> > I've done some resistance checking on V701 and nothing is all that far
> off.
> > Since the slug tunes the plate tank, I'm wondering if the problem might
be
> > with C706. It's supposed to be adjustable, but how? Reading the Y2K
> > manual, it states C706 is a variable glass dielectric cap. Not sure
what
> > that is, but with the PTO out of the radio and the cover off of Z702, I
> see
> > a clear cylinder in which the slug moves. Is that C706?
> >
> > Thanks for any help or advice on this.
> >
> > Barry - N4BUQ
> >
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