[r-390] Critical Issue

Thu, 4 Sep 2003 14:07:23 -0700 (PDT)

Barry,
I was discussing the cap in the R-390/391. This is/was a tantalum disaster that contained a surprising amount of acid. This together with the considerable heat in the R390 can cause a surprising amount of damage. The cap in the R-390A is a more modern variety I think. Collins modified the circuitry of the R-390 quite early on to eliminate this cap altogether.
Dave

Barry Hauser <[email protected]> wrote:
Hi Dave & Gang:

I didn't realize that the non-A and '391 also have this cap, or do they? Is
it the same type of small axial metal tantalum that's on the component board
in the R-390A audio module? I finally found one out of about 12 that didn't
toss it's cookies. But usually the damage is limited to a 3/4 inch round
splotch on the board and the two components alongside it. The 8uf tantalum
(C609) is fairly small and doesn't have enough acid to do much more than
burn a small crater in the board.

A good photo is on Chuck Rippel's site http://www.r390a.com/ProbCaps.html
Scroll about halfway down to see C609. Some vary in style a bit, but
they're all about the same size. They usually don't look as neat as the one
in Chuck's photo.

Barry

----- Original Message -----
From: "David Medley" 
To: 
Sent: Wednesday, September 03, 2003 8:20 PM
Subject: [r-390] Critical Issue

> I am presently working on an R-391, a very old one. The audio deck was
original without mods. The following is an exerpt of a message I just sent
the owner. Anyone who owns an R-390 or R-391 should check this out. This
damage can be horrific.
>
> "The radio is disassembled completely. I have finished overhauling the
audio/VR deck which is the most time consuming part. This one is very old
and did not have any of the later mods. I have brought it up to date and
replaced all critical parts. One of the bad things with these early
assemblies is the 8uf cap in the audio section. This thing leaks acid over
time and I have seen cases where complete replacement of the circuit board
was needed and extensive cleanup of the chassis as well. If you have any
other R-390/391 radios you should check this out. The mod is simple and
eliminates this cap. In this one the cap had not started to leak so no
damage was done."
>
> Please note this applies to R-390/391 radios although I believe there may
be a similar problem with early R-390A radios.
>
> Dave
>
> P.S. If anyone has this problem and needs help please let me know.
>
> .
>
>
>
> Sincerely
> David Medley
> [email protected]
> If you have a minute please check out:
> http://www.adminder.com/c.cgi?davidmed&123
> You might even make some money!
>
> --- StripMime Report -- processed MIME parts ---
> multipart/alternative
> text/plain (text body -- kept)
> text/html
> The reason this message is shown is because the post was in HTML
> or had an attachment. Attachments are not allowed. To learn how
> to post in Plain-Text go to: http://www.expita.com/nomime.html ---
> _______________________________________________
> R-390 mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/r-390

Sincerely
David Medley
[email protected]
If you have a minute please check out:
http://www.adminder.com/c.cgi?davidmed&123
You might even make some money!

--- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/plain (text body -- kept)
  text/html
The reason this message is shown is because the post was in HTML
or had an attachment.  Attachments are not allowed.  To learn how
to post in Plain-Text go to: http://www.expita.com/nomime.html  ---