[R-390] Servicing Advice on Signal Generator URM-25D

[Dallas Lankford]

I have never seen a black capacitor in an R-390A.  You must be confused.
The bad black capacitors were in the SP-600's (except for some of the very
last production, which had disc ceramics).  If any of those black beauties
were in an R-390A, you wouldn't have to test them to figure out they were
bad.  You could see the cracks.  I seem to recall that there were other
black capacitors from the 50's that were O.K., but don't quote me on that.

Have fun,

Dallas


----- Original Message -----
From: "Bob Camp" <ham at cq.nu>
To: "Dallas Lankford" <dallas at bayou.com>
Sent: Monday, January 10, 2005 8:13 PM
Subject: Re: [R-390] Servicing Advice on Signal Generator URM-25D


> Hi
>
> Thanks for the information, it's not what I expected to hear.
>
> Last time the question came up there where no replies that indicated
> any tested good black beauties in any of the R390's. Since I have never
> seen any either that was what I was basing my recommendations on.
>
> Take Care
>
> Bob
>
>
> On Jan 10, 2005, at 8:46 PM, Dallas Lankford wrote:
>
> > Every one I have ever checked from an R-390A was good.  Every black
> > one I
> > ever saw from an SP-600 was bad.  But if you want to replace R-390A
> > capacitors anyway, I am sure you will.
> >
> > Dallas Lankford
> >
> >
> > ----- Original Message -----
> > From: "Bob Camp" <ham at cq.nu>
> > To: "R-390 HF Receiver List" <r-390 at mailman.qth.net>
> > Sent: Monday, January 10, 2005 7:43 PM
> > Subject: Re: [R-390] Servicing Advice on Signal Generator URM-25D
> >
> >
> >> Hi
> >>
> >> I asked this back a few years ago and maybe it's time to ask it again.
> >>
> >> Has anybody seen any of the black or brown body / epoxy coated paper
> >> and foil capacitors made in the 1950's and 1960's show up good?
> >>
> >> As originally asked the question was specific to the R-390. Since then
> >> I have seen a bunch of posts on a number of reflectors about these
> >> parts. They all seem to indicate these parts are a problem.
> >>
> >> At least in my experience, testing pulls from a couple dozen radios
> >> they show up leaky (as in 5X out of their original specification)
> >> roughly 80% of the time. They show up at least 2X the specification
> >>> 90% of the time. Certainly there are places where you will not notice
> >> leakage even if it is 5X the specification. Most of these seem to get
> >> used in high impedance circuits where you will notice the effect
> >> though.
> >>
> >> Take Care!
> >>
> >> Bob Camp
> >> KB8TQ
> >>
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