One
of the most common
maladies of old rigs, is dried up and/or leaky capacitors.
It's easy enough to purchase a new one, and stick it under the
chassis, but sometimes it's nice to
keep the chassis looking original. I don't take the time to do this all
the time, but on a particularly nice unit, it's worth the effort, and
really doesn't take too long. If you have a better solution for the
ground wire, please send it along.
A typical old
chassis mount
filter cap,
4uF at 600 volts. I've sawed off the end with a
dremel cut off wheel right below the rolled on crimped tin seal. The
dremel saws through the aluminum with a very small and
neat kerf, making it easy to epoxy the pieces together after
re-stuffing the can
with a replacement.
Pushing
the cap guts out from the threaded mounting end... it's a messy job!.
The inside can be cleaned out with soap and water .
You stand
to
lose "valuable husband points" if you do this on the kitchen table, and
the stuff is probably known by the State of California to cause some
type of cancer. That being said, this step is best performed outside,
or during opportune moments coinciding with long outings by the
Significant Other.
Here's the new caps ready to install. I'll cover
these with
heat shrink to insulate them and provide some mechanical strength.
A small lug with #2 hardware applied thru the side of the
can,
will provide a ground connection for the negative lead of the can.
Since the lid (which can be soldered to) will only be epoxied back on,
it can't be relied on to provide a ground connection. I wish I had a
better method for this, but it's the only thing I know to do to provide
a ground connection. The threaded stud shown, was cleaned up and will
be soldered to for the positive connection. Insulating shoulder washers
isolate it from the can. I've also used wooden button plugs (available
at the big box stores) painted black, for this purpose. They fit the
neck well.
The new caps are in series to provide the proper working
voltage.
Since the outside shell of one of the caps is well above ground, heat
shrink is applied to prevent shorting to the aluminum shell of the
original can.
After inserting the new caps in the original shell, the
rolled lid
is epoxied back on, using JB Weld. This is great stuff, and
it's
pale gray natural color blends well with the aluminum can. Note the
insulating washers at the threaded end, and the stud which is connected
to the positive terminal of the capacitors.
While it might seem a lot of work, this whole process take only about
an hour to do. It's won't pass a careful inspection, but it's
nice to keep open chassis rigs looking original, and keeps the under
chassis layout neat. It will be replaced in the original
location
with its large stamped steel nut. It's
now good to go for another 30 years of service!
