{Collins} Re: 75S-1 Ceramic Variable Capacitors

[Glen Zook <gzook@xxxxxxxxx>]

If you are careful you can refurbish those capacitors.

On the underside there is a "clip" to which one side
of the connection to the capacitor is made.  You can
use a pair of needle nose pliers to slide this clip
from the center post (you do not have to remove the
wire).  This will allow the assembly to be removed
from the top.

There will be soft "rubber like" insulating material
with an oval hole in it and then the rest of the
capacitor.  The capacitor itself consists of a very
thin ceramic disk and then the remainder of the
capacitor.

Soak the parts in warm, soapy water for a few minutes.
 You have to be VERY careful to get the ceramic disc
"unstuck" from the body of the capacitor.  I use an
Xacto knife with a NEW #11 blade.  You CAREFULLY use
the sharp edge of the Xacto knife inserted just where
the disc and the main part meet.  This will "break"
the disc away from the main part of the capacitor.

Wash all three parts in the soapy water (I use
dishwashing liquid for the soap) and dry very
carefully with a soft cloth.  

You will note that the disc has plating over about
half of it.  When reassembling the capacitor position
the soft rubber disc so that the "fingers" on the
phenolic base go through the hole in the insulator. 
Then position the disc so that these fingers come in
contact with the plating (the plating will face
downward).  Next put the rest of the capacitor back in
place (the metal pin will go through the hole in the
ceramic disc, the rubber insulator, and the phenolic
base).  Finally slip the "clip" back onto the pin
making sure that the "dimple" on the end where the
wire connects goes into the very small hole in the end
of the phenolic.

As I said above, you have to be VERY gentle when
loosening the disc from the body of the capacitor.  I
have to clean the ceramic variable capacitors in quite
a few S-Line units that I align/repair for others and
have acquired the "knack" for cleaning them.

If you do not want to clean the capacitors and can
find replacements you do not have to remove the old
capacitor bases from the unit (requires soldering and
removing the screws).  If you remove the "clip" from
both the replacement capacitor and the original
capacitor you can take the new rubber insulator, the
new disc, and the new body and put them in the
original phenolic holder.  Then replace the "clip" and
you are ready to go.

By the way, there are actually 2 different values of
these ceramic capacitors in the unit so you have to be
careful not to get the wrong value inserted.

Glen, K9STH


--- Bill Scurlock <k5gcw@xxxxxxxxxxxxx> wrote:

I'm refurbishing a 75S-1, and finally got to the
alignment part where I discovered that 3 of the
8-50mmf variable ceramic capacitors appear to be
mechanically damaged.  They are easy to turn, but do
not seem to be changing value since there is no affect
on the circuit tuning.
 
Does anyone have any they would sell?  or, is there a
source of a substitute that will physically fit in the
mounting hole?  Does anyone know how to repair these
when this happens?










Glen, K9STH

Website:  http://k9sth.com


       
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