[R-390] R-390A trouble

[Jim Temple]

Hi Roger and list,

OK, I want to fix this receiver.  Here goes.

1.  R-390A bought as a "massacre" yellow line from Fair Radio.
2.  After cleaning, and replacing many of the "problem" caps (listed on many
of the resident web sites), I corrected a below 8mhz problem, by finding
that the ground lug under T-207 was loose and insulated from ground by a
shellac layer.
3.  The unit, at first alignment, aligned well.
4.  At some point, within a couple of hours of operation, the receiver
developed a screeching/motorboat putt putt sound.

Symptoms:

1.  On bands 00,01,02, and 03, the screeching/motorboat sound is not
present.
2.  Above band 03, the motorboat sound will vary in amplitude and putt, putt
frequency with adjustment of the antenna trim control, and becoming more
intense as band increases.
3.  The carrier level meter indication increases as the amplitude increases,
the strongest coinciding with the antenna trim peak prior to the problem
developing.
4.  The AGC control will change the frequency of the putt,putt, depending on
the position of the control.  Fast=fast.  Slow=slow, or right on the edge of
putt,putting.  Medium=medium frequency.
5.  The AGC voltage measures about 8-9 volts during the motorboating.
6.  The screeching/motorboat sound disappears with removal of V201/'6DC6.
7.  I replaced the antenna trim assembly with a spare from a spare RF deck,
with no change.
7.  The ohm reading of the antenna trim vertical shaft is 1.5meg, and
doesn't vary with rotation of the control.
8.  With the RF deck removed the antenna trim wires measure a smooth
increase and decrease of the variable caps within the enclosure.

I have inspected and examined the bottom components of the RF deck several
times and can find no shorts or broken wires.
I am positive the RF deck timing is correct.  I have triple checked the
timing and am positive it is correct.  The deck did work fine for a couple
of hours.

My troubleshooting skills are lacking, so sometimes I do not approach a
problem in a logical fassion.

My approach will be to thouroughly examine the RF deck components.  Measure
the values of components I reasonably can.  I thought the voltages in the
Y2K manual were measured with the tube in place, but I am unsure at this
point.

There is clearly a great deal of knowledge and expertise on this list, so I
hope my lack of troubleshooting skills will not get in the way of a fix to
this receiver.  I may need a little more "hand holding", detailed coaching,
than the average owner.

Thanks for listening.  I hope I have given enough detail to get me started
on the right road.

Sincerely,

Jim
73, KF4ICZ

----- Original Message -----
From: "Roger L Ruszkowski" <rlruszkowski@Raytheon.com>
To: <r-390@mailman.qth.net>
Sent: Wednesday, March 27, 2002 12:01 PM
Subject: Re: [R-390] Fw: Alignment help.more


>
> Jim,
>
> What are you doing to an R-390/A.
snip....
> List your problems here and get some specific help.
> Quit trying to solve and reinvent it all by your self.
> It is more fun that way. I do agree.
snip....
> What is your real objective?
> Do you want some tube extenders, or do you want to fix a receiver?
>
> Roger KC6TRU San Diego.
>