[R-390] Detector tests followup

[Barry]

Tried swapping another NOS 5814A for V506.  Didn't notice any real
differences; however, something happened tonight as I was tinkering with the
radio.  It was as if a switch suddenly turned on and the noise level with
the BFO in the off position came up rather noticeably.  Not sure what's
going on.  I did poke around the innards of the various IF transformers just
flecking off any loose varnish, etc., making sure things were connected
well, etc.  Not sure if that might have had an effect or not.

At any rate, I started tuning around.  Radio Tiawan International (5850(?))
was coming in extreeeeeemely loud.  If I switched to MGC, the carrier-level
pegs and I have to back off the RF gain just a bit to get normal audio.
Switching to AGC works great with signals around 80dB.  Is this normal?

While I can't seem to get that elusive 0 VU or better with 150mV on the
detector, the radio seems to be playing quite well and I'm beginning to
wonder if I'm chasing ghosts.  I'm just about ready to do the final
alignment, put the covers on it, and enjoy it for a change.

Barry - N4BUQ

----- Original Message -----
From: <n4buq at knology.net>
To: "Cecil Acuff" <chacuff at cableone.net>; <r-390 at mailman.qth.net>
Sent: Wednesday, September 20, 2006 2:12 PM
Subject: Re: [R-390] Detector tests followup


>
> > Checked 6 ohms for both windings; however, I don't get infinity between
> > coils when the deck is connected to the main harness.  If I disconnect
> the
> > diode load, the windings show infinity between them so something
> downstream
> > of the diode load is providing a high-resistance between the windings
> > (about 50k).  I notice this varies a bit when turning on/off the
> limiter.
> > Perhaps the circuit ties back from the centertap of the primary back to
> the
> > limiter.  I briefly looked into that but was on my lunch break and
didn't
> > look at all the places where this could provide a high-resistance shunt
> > between the primary and secondary windings.
>
> Okay, did a little schematic reading and see where there are paths from
> both the primary and secondary to ground through a series of resistors so
> with the main plug and the diode-load connected, there should be some
> resistance reading between the primary and secondary of T503.
>
> Perhaps I do need to do some tube-swapping.  I thought I had a good one in
> there but maybe not.
>
> Barry - N4BUQ
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