[R-390] If those Capacitors could talk

[rbethman]

  My point of those BBODs and Brown versions, is that I have been 
restoring some St. J's survivors.  They are ALL "Bad News Beaars!", get 
RID OF THEM.

Look for ANY brown postage caps.  These TOO are plastic covered paper caps!

So far, I haven't found issue with the "red" silver mica caps.

Resistors are DEFINITELY "suspect".  They are carbon composition types.  
Aside from age, they have been exposed to heat and moisture!

By ALL means, TEST and REPLACE out of Spec items!

I do NOT go Willy Nilly in replacing components!  I've found the plastic 
coated silver Sprague caps to be fine, along with those yellow Aerovox, 
(or whatever the brand is), to be perfectly in tolerance and nil leakage!

Those "acid electrolytic" caps on the audio board MUST go!  Check all 
THOSE resistors TOO!  Replace as found out of spec!

Bob - N0DGN

On 9/12/2010 1:24 PM, wa4aos at aol.com wrote:
>
>
> I have repaired/restored more R 390A and R 390 receivers than I care to remember. From my experience I can honestly say most of those caps would say, "Leave me alone, I'm just fine."
> While  some of the resistors are screaming, "change my diaper, I can't handle anymore load ! ! !"
>
> In the beginning, I shot-gunned all of the 18 standard bypass caps in the IF modules as well as 4 on the RF deck and the others on the audio module. Most of the canned Electrolytic
> caps, C603 and C606, on the Audio modules have been physically and Electrically leaky. That is to say, you will often see white crud coming from the base and when tested for leakage at voltage, they test leaky.
> I see this so often that I buy batches of these from Sigma Technologies in Germany. He advertises on ebay and makes a great replacement capacitor set. I have used the ones from Hayseed electronics as well and they are also good.
> I test capacitors for value with a digital tester and for load/leakage with a Sprague TO6 tester which test the capacitor at or near it's operational voltage.
>
> Here is what is interesting, out of the yellow or aluminum bypass foil caps I have tested, I have found far less than 1% to be the least bit leaky. all most all of these test and work excellent. And actually, 85% or more of the black beauties also test fine.
> I know it can be argued that these capacitors are in some cases are near 50 years old or older; that is a good argument. However, I so often hear and see people looking for NOS, New Old Stock orange drops. God only knows how old those might be or how many years they sat year round in a hot and cold warehouse. I buy only NEW Orange Drops from Mouser and I believe they are all made by Vishay now.
>
> I actually find far more resistors out of spec than capacitors. I have yet to work on an IF or RF module that did not have 3 or more resistors seriously out of spec. I believe more detail is paid to the capacitors, in part, due to the fact changing out some of the resistors is more involved. I guess ignoring them makes the problem go away???????