‘Restuffing’ a capacitor is the art of repairing old capacitors by replacing
the electronic component inside with modern capacitors and therefore
retaining the original outward appearance while making the part again truly
functional. It is a well debated fact that almost nobody will ever look
under the chassis of your old radio to see if the capacitors look original!
However for some restorers, the satisfaction of retaining the complete
originality of the radio while also making it work well and safe to use is
most satisfying.
In our series of capacitor ‘restuffing’, the box type capacitor is by far
the easiest restuff to perform. This capacitor seen here is from a Crosley
148 cathedral. My radio is in excellent, almost mint, all-original condition
top and bottom, so I felt that some extra effort restuffing would be
justified in this case. |
 |
To begin, the capacitor needs to be removed from the radio. In this example,
the box contains two separate capacitors within the same package. Be sure to
label where each connection goes and what the connections on the box are (+,
-).
After removal and a quick cleanup, the box may be disassembled by
carefully heating it with a heat gun on low heat and a lot of
patience. An oven on low temp (200-250 degrees) will work too,
|
 |
as long as the oven is pre-heated
and the heat turned off when the cap is inside. Most of these types
of caps use wax to hold them together and to fill the void inside
the box. This wax melts easily and will not harm the cardboard or
paper when leaving the box. Sometimes, the wax dries out enough so
that you can just pull it out without heat. It is important to
remove as much of the wax from inside as possible. I like to
completely unfold the box and clean it while flat. |
Next, you must remove the capacitor components themselves. Either cut or
desolder the connections from the tabs and carefully work the parts out of
the box. If you have removed enough wax, they should practically fall out.
Next, get another capacitor component or components of the proper value and
voltage capability to replace the old one(s). It is appropriate to increase
voltage capability to any value higher than needed, but you should not
increase the capacity too much above the original value. For the radio that
uses this capacitor, the original value was 6 and 8 uF, but in examining the
circuit, I found that 22 uF was not only better but also the circuit could
easily handle the extra peak current to charge them, so I chose 350 volt, 22
uF capacitors for the restuff. |
 |
| Now, you have to reassemble the box and get it ready for the new capacitors
to be placed inside! Gluing the box back together is difficult since the
cardboard is saturated with wax. I have found that a 50-50 mixture of
Ambroid cement and lacquer thinner makes great glue for this. The lacquer
thinner cuts through the wax and the Ambroid dries quickly and is thinned
with simpler lacquer thinner if you need to disassemble the box in the
future. Use Ambroid/thinner on all seams and assemble as much of the box as
possible at a time. Clamp the box until the Ambroid mixture dries completely
(about an hour). |
 |
Solder the new capacitors into the box and be sure that the positive (+)
terminals go to the proper tabs on the box. The negatives go together to the
terminal. Wrap the wires around the terminals and solder them in
place. If you do not wrap the wires around the posts or position them inside
holes in the posts, they may come unsoldered when you reinstall the cap in
the radio. After installing the new capacitors, it is a good idea to retest
with a cap meter before the next step to make sure the connections are good
and the caps have not been damaged by heat. |
|
  |
|
Now, the filling material must be selected and added to the box. I prefer to
use silicone sealant because it is heat resistant, non-conductive, and can
be removed in the future if needed. It also cushions the capacitors inside
the box. Begin by working the silicone into the area under and around the
new caps, filling in all areas. Fill with silicone until you can level out
the material. |
With the insides filled, you must reassemble the box before the silicone
completely dries. Once you level the silicone, close the top and glue it
shut. Ambroid does a great job of this too, and if you get a little outside
the seam, it will hardly show once dry. Test the completed cap one more time
before installing it in the radio.
Using the computer and a laser printer, you can recreate the original labels
too! To 'antique' the paper, soak it in warm water with either instant
coffee or tea (depending on the color you wish) and let it dry. Then print
your computer generated logo on the paper and glue it to the capacitor. I
used simply craft glue sticks to do this. |
 |
|
  |
|
Is it new or old? Be sure and make a label to hide somewhere
on the 'new' old capacitor so the next person to work on the radio does not
rip out all of your handiwork! I place a tag on my caps with the word
'RESTUFFED' and date the restuff took place so I know how old the insides of
them are. |
Next time, we'll restuff some typical small value wax/paper caps in a
Crosley tabletop.
|
