PHILCO BAKELITE CAPACITORS:
REBUILDING THEM
Philco started using the new Bakelite Capacitors in June of 1930 in their models 30, 41, 77, and 96.  These were phased out in the late 1930’s and were replaced by paper capacitors.  But the bakelite blocks were used in the AC line filters as late as 1948.
The blocks consist of a bakelite shell with capacitors wired to appropriate terminals and sealed with a “tar” or “pitch” mixture and a single self-taping metal screw, that sometimes also serves as a chassis ground.  Terminals riveted to the top of the shell provide connections for the capacitors inside the shell.  Often extra terminals were added to serve as tie points for wiring.
The PHILCO Part Number is Hot stamped on the side of the shell and the very late one’s have a yellow painted part number imprinted on the side.  The letter ”O” in the part number means that it was filled with a high temperature wax, and letter “G” means the block is grounded to the chassis, and the letter “U” means that it is ungrounded.
A paper-dielectric capacitor that is inside of the shell is shown at the top of this page.
Now a word to the wise that MOST other site’s don't tell you.  SOME of the bakelite blocks have resistors in the blocks consisting of a hank of insulated wire folded in a figure eight (8) inside a very small envelope, and 110 and 250 pF paper capacitors.  DO NOT use 0.001 caps, instead use 100 or 250 pF mica capacitors and the suitable resistor.  Most of these blocks start with 8035- something.

The VERY FIRST thing to do when rebuilding the blocks is to color code the wiring with a dab of paint on a touch up-brush and make a drawing of the block and what wire goes to what terminal.  Then just cut the wire as close to the terminal as possible and remove the block from the chassis.
I have a small vise shown at the top of the page that I clamp the block into and a small pocket screwdriver to dig the “tar” out in chunks.  If it will not come out I use a hair dryer to heat the block up.  Be careful the block doesn’t break.  Use a small pair of wire cutters and cut out the wiring of the block inside.  Then I have a jar half filled with lacquer thinner to put the block in to shake vigorously, washing out all of the “tar”.  Re-clamp it back in the vise and clean the solder off the terminals and the wiring out of the eyelets.  Take a drill and drill out the eyelet holes.  Put the capacitors and resistors in and the wire though the eyelet and re-solder it and snip off the excess wiring.
I refill the blocks with a caulking gun and a tube of “DAP” Blacktop Driveway Sealer.  DO NOT use silicone sealer.  Put it into the freezer for about 15 minutes and reinstall in the chassis.
Use the next two (2) pages as a guide for the capacitors and resistors.
For information on Metal Case Capacitors
For information on Tone Control Capacitors
For information on Multi-section Case Capacitors and
Electrolytic Capacitors (Big Black Box’s)