Fw: [R-390] R-390A trouble (BIG CORRECTION)

[Barry Hauser]

Jim --

Did you originally find a 6DC6 in that socket?  There was a thread on
subbing the 6CB6 as I recall, but to make use of it involved changing a
resistor as there is a difference in gain between the two (not sure).  Maybe
the deck was "converted".  A long shot.

Barry.



> OK, I cleaned all the tube pins and sockets with DeOxit.  I replaced them
> one at a time.  No problems till the last tube, RF amp/6DC6, when the
putt,
> putt came back.  I scratched my head and, one at a time, removed and
> replaced the preceeding tubes.  In all instances the problem went away.
So
> I am unsure as to what stage is the problem.  When I removed Y202, the
> problem went away below 8mhz and returned above 8mhz (as expected).
>
> Jim
>
> ----- Original Message -----
> From: "Jim Temple" <jetemp@insightbb.com>
> To: "Roger L Ruszkowski" <rlruszkowski@raytheon.com>
> Sent: Thursday, March 28, 2002 6:17 PM
> Subject: Re: Fw: [R-390] R-390A trouble (BIG CORRECTION)
>
>
> > OK, just to make sure I am on the same sheet as everyone else, I want to
> > repeat what I know up to this point.  Let me know if I'm messed up.
> >
> > 1.  The problem occurs at the same point of travel of the RF gain knob,
> > approx 9.
> > 2.  The problem is putt, putt on AGC, and receiver block in MGC.
> > 3.  The carrier level and agc voltage increase in AGC, with an increase
in
> > RF gain after start of problem.
> > 4.  The carrier level JUMPS to 100 in MGC at start of problem.  (I
> > understand that overdriving in MGC will produce an indication on the
> carrier
> > level meter).
> > 5.  The setting of the IF gain control makes no difference, whether AGC
or
> > MGC, or above or below the point of the start of problem.
> > 6.  Substituting a known good IF deck makes no difference in symptoms.
> > 7.  All coax shields between RF deck, IF deck, and crystal deck show
> > continuity
> >
> > To reitterate the below procedure, I will pull all the tubes from the RF
> > deck and crystal deck, and PTO.  I will replace them in the order or 3rd
> > mixer, PTO, 2nd mixer, crystal deck, 1st mixer, and RF amp.  The point
> where
> > the problem starts should identify the stage of approximate problem.
Here
> > goes.  I will report back.
> >
> > Thanks,
> >
> > Jim
> >
> >
> > > Pull the tube off the RF deck and start them back in
> > > third mixer
> > > PTO,
> > > second mixer
> > > 5654 6ak5 on the crystal deck
> > > first mixer and 17MHz osc it is not because it does it over 8.
> > > 6DC6.
> > >
> > > Once you find the stage and the signal level to inject to get the
> > > problem to putt, putt your only close. You still will have to find
> > > the problem under the deck.
> > >
> > > Pull all those tubes up and clean the socket pins.
> > > De oxit if you can, use what you got.
> > > work the tubes in and out 4 or 5 times.
> > > If you just got a pin with crude or oxide, you mite as well
> > > just short gun it and get over it.
> > > As it putts on more than one band, 2-3, 4-7, 8-16 you
> > > know it is not in the cans and slugs on the top side or there
> > > trimmer cap in the top of the cans.
> > >
> > > Roger.
> > /mailman/listinfo/r-390
> >
>
>
> _______________________________________________
> R-390 mailing list
> R-390@mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/r-390
>
>