[R-390] Re Troubles, B+ capacitors

[Tisha Hayes]

Quotes:
---------- Forwarded message ----------
From: Greg Rainwater <w7acm at comcast.net>
To: r-390 at mailman.qth.net
Cc:
Date: Mon, 02 Jan 2012 17:47:34 -0800
Subject: Re: [R-390] Troubles.
On my R-390A the blowing fuse was a bypass cap in the B plus line in
the Audio module.

Greg
W7ACM

On 1/2/2012 5:35 PM, ToddRoberts2001 at aol.com wrote:
I have run into several R-390A's blowing fuses  at turn on. It always
turned out to be the large metal plug-in filter caps  C-603, C-606
located on the audio module. Once I replaced those with  new
capacitors, the problem stopped.

73 - Todd WD4NGG
End Quotes:

That is exactly the same opinion I share. You really do not want to to
that very many times as you can toast the chokes on the B+ supply.
When you replace those two plug in caps you may want to check your B+
voltage and also add the B+ fuse mod if you do not have it in place
already. It is pretty hard on the tube based or diode rectifiers as
well.

I would suggest either purchasing a set of restuffed plug in
capacitors or going under the deck and adding capacitors and leaving
the sockets empty. Try to use something like a 400 volt capacitor if
you can manage to squeeze it into the same place.

Old, NOS capacitors will need to be reformed, even if they were never
plugged into a radio before. Electrolytic capacitors of that vintage
will dry out just from sitting on a shelf. They age even faster in
storage than they would under light duty service. Anything you are
buying that is NOS/NIB is probably at least 15 years old. There has
been a great deal of evolution in modern capacitor design (better
films, better foils, better electrolytes). I am sort of a fan of
Sprague but I do not know if they still manufacture in the octal based
plug in caps of those values. Sometimes the capacitors you can find
are too tall and you would not be able to put the bottom cover plate
on. Watch the dimensions carefully.

There are plenty of YouTube videos on how to restuff the capacitor
cases with newer capacitors and how to drill out the pins or solder
the capacitor leads onto the octal plug in base. Usually the only
thing that gets ugly is if you saw the bottom off and leave an ugly,
jagged edge that you just jam onto the octal base plug. I have seen
some very good work done where people take the time to clean up the
edges of the capacitor cans and roll their own crimp onto the aluminum
base or they are artists with JB Weld. Note: taking apart an old
capacitor will probably require you to work with boiling hot water to
loosen up the pariffin that holds the guts in the old cap or maybe
even a torch to soften things up. Wear gloves, work in a ventilated
space, use teflon spagetti on the new leads and take your time if
doing this on your own.

-- 
Ms. Tisha Hayes/ AA4HA
-
“But what is liberty without wisdom, and without virtue? It is the
greatest of all possible evils; for it is folly, vice, and madness,
without tuition or restraint.”   Edmund Burke