[R-390] Gain Problem

[Bill Smith]

Aside from the frustration implied by the poster, there is not a little
frustration in this reader.   Rant deleted.

Several things to check jlap, they shouldn't be difficult.

(1) Complete R-390 documentation is on-line.  I downloaded and printed it.
It was difficult to line up the pages so that it could be printed front and
back, but I took the effort and have a good manual as a result.   Yes, I
searched to find a utility to print the schematics, but free IrfanView has
turned out to be invaluable for a number of other needs here also.  Yes, I
later found an original manual, but it is an earlier edition.   Both,
together are sound documentation for the receiver.  Either are more than
enough information to answer your question re the Local Gain pot.

(2) The 390/390a have similar, if not identical audio circuits.  Seems the
only thing that could cause loss of gain control would be a defective pot or
bad ground connections to the pot.  You will observe the Local Gain pot is
located at the bottom of the receiver front panel.  Have you examined the
connections to make sure they haven't been phycically bumped by moving the
receiver around?   The ground wire(s) to the pot may have broken.

(3) R-104, the 2500-ohm Local Gain pot may be defective.  R-105, a 1200 ohm
resistor is connected across the outside terminals.

(4) The wiring to the audio module may be damaged.  You may have a broken
ground wire inside a plug.

(5) A quick look at the circuit will show that there are no sneak paths
around the Local Gain volume control.  Audio from the receiver is wired
directly to both the Line Gain and Local Gain pots.

The R-390/R-390a receivers may easily be classified as high-maintenance
equipment, the best and most sophisticated of their age.  They were also
designed to be servicable according to the technology of their age.

73 de Bill, AB6MT
billsmith@ispwest.com



----- Original Message -----
From: jlap1939@yahoo.com
To: r-390@mailman.qth.net
Sent: Thursday, July 31, 2003 1:21 PM
Subject: [R-390] Gain Problem


Hello Friends,

Will stay as short as I can...Must enter defense
first..!!  This however will not be short...

When I received my 390 back from David, I hooked it up
to the reciever monitor, and set it for SSB on the ham
bands..As a result I don't know when the problem
developed, or why it did..as I was hearing all at 6
local, 6 to 8 rf, by adj. of the monitor vol. I never
touched the local. I use headphones for SWL on the
600, as a rule. The monitor is a very good amp and
runs at a low level whatever you put into it... (This
is my defense for not having noticed anything
wrong...)

Decided to chase a little SWL that I was not getting
clearly enough on the 600, and guess what?My 390 Local
Gain is running wide open all the time...Have to use
rf gain to set a listening level, which means I am
getting noise in the system I would not normally have
it seems.(By the way, Phils' stuff was great reading
for a change..I think it is reasonable material for
this forum, and checked out the stations myself, (But
not with total sucess...but thats another story...))

Questions?   YES:  Likely the pot, or might I look at
something else ..(Either sooner or later), as the
cause..??  and having only partial schematic and
little knowledge of 390 , how do I start? How do I use
the line output, and would that be a temp. remedy???

Funny, having bought and worked on a  blue striper, I
can do much on the 390a,inc a good align, due to THE
21ST CENTURY R-390A/URR REFERENCE. But I like and own
the 390...Wish there was a way to learn  the more
complex 390 that would help me...or maybe I may yet
just get and KEEP a 390a...??

I covet your help and sympathy..Regards,

John    (JLAP)

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