[R-390] R-390 Digest, Vol 81, Issue 29

[Tisha Hayes]

The 1) Paper capacitors I refer to are those that look like a cardboard tube
(miniature toilet paper roll), usually tan or brown in color with paper end
caps.

Yes, the BBOD's and a bunch of other capacitors are paper with some form of
dielectric (oil or some electrolyte). The BBOD's became notorious because
their cases would frequently crack along a seam and the cap would get very
leaky, suffer significant changes in value or just short out.

Another bad cap is the 8 uFd C609 tantalum capacitor in the audio deck. It
is rated at 30 VdcW and has a tendency to spew out an acidic compound that
will eat up neighboring components.

On the IF deck the 0.01 uFd paper capacitor (C553) should be replaced before
it fails in a shorted mode and takes out the IF filters one-by-one as you
rotate the bandwidth switch.

The audio deck is filled with paper caps, the IF deck has a few.

If you are not working from a good set of manuals that include the
modifications try to get a set of the Y3K R-390A. The manual is free (12
chapters) and runs around a 30 megabyte download.

(   http://www.r-390a.net/Y2K-R3/  )

Tisha Hayes
AA4HA