[R-390] Resistors for the R-390A and beginner help

Mon, 13 Jan 2003 20:34:28 -0500

----- Original Message -----
From: "Jim Miller" <[email protected]>
To: "Ronald Davis" <[email protected]>; <[email protected]>
Sent: Monday, January 13, 2003 8:32 PM
Subject: Re: [R-390] Resistors for the R-390A and beginner help


> My opinion:  After restoring a 51S1, KWM-2A, two 75S3B's, a 32S3, a 75A4
and
> two R-390a's, here is my advice:  Don't replace the resistors unless you
> have to.  As they age they do tend to drift out of tolerance.  The best
way
> I know of is to get a diital VOM and measure each one (in a hi impedance
> tube circuit you can usually measure most of them at the tube socket pins
> without unsoldering one end, power off of course).  if they are within
> spec-ed tolerance (e.g. 10%), leave them alone.  if they look blackened,
> swolen or burned, then they are good candidates for replacement.  In my
> experience with the above radios, the the resitors that have tended to be
> out of tolerance have been screen resistors, resistors in the plate
circuit,
> or cathode resistors, since they are usually carrying the most power.  Do
> not use wirewound resistors to replace carbon resistors as they have an
> inductive characteristic.  Also, beware of "black beauty" capacitors.
Check
> some of the various restoration pages for a list of problem capacitors
that
> should be replaced immediately, such as ithe cap. that couples to the
> mechanical filters in the IF module.  And tighten all hardware, especially
> screws that mound tube sockets to the chassis.  Repeated heating and
cooling
> cycles will cause them to loosen resulting in poor grounding ove time.  Do
> not spray bandswitches with contact cleaner or deoxit... in high impedance
> circuits the residue will conduct enough to screw up the circuit
> performance, especially AGC.   If you have to, use a very small swab to
> selectively clean switch contacts.  As soon as the rotary switch phenolic
> material absorbs the spray, you're outta luck.  Good luck.  Jim N4BE
>
>
> ----- Original Message -----
> From: "Ronald Davis" <[email protected]>
> To: <[email protected]>
> Sent: Monday, January 13, 2003 2:51 PM
> Subject: [R-390] Resistors for the R-390A and beginner help
>
>
> > Hello
> > Im getting ready to start working on one of my R-390A's and im wondering
> if
> > anyone has a part number list for all the resistors? Sure would save
alot
> of
> > time if someone had all the mouser numbers in a excel spreadsheet for
all
> to
> > use. I have a recap kit coming, but what is the deal on the resistors,
> does
> > everyone just replace the bad ones, or is it worth it to replace them
all.
> > This radio is going to be home use rig and I want it to be in perfect
> shape.
> > Got to get my a small tv/vcr for the shop so I can watch the videos
while
> im
> > working on the rig, my memory is not to good anymore hi. I have a nice
> > Hammarlund HQ-170A with Hammarlund speaker that I would trade toward a
> > R-390A or R-392? Anyone interested? Email for pics
> > Thanks
> > Ronnie
> > KE4VPN
> >
> > _______________________________________________
> > R-390 mailing list
> > [email protected]
> > http://mailman.qth.net/mailman/listinfo/r-390
>