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

[Jim Temple]

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
>