[Guest]

Hi again,

I'm looking over the bakelite blocks I'm rebuilding currently and I was curious if there is data for the original configurations. I wanted to be sure there were no resistors in these blocks as well as keep the "pinout" intact for rewiring purposes.

3615-AM, 8035-K (actually installed -L), 3903-AN, 3615-H, 3903-J, and 3793-H are the part numbers.

Of course, I'm now curious about the tone control too - are there capacitors in that as well?

Thanks!
-Chris

[Doug K.]

Bakelite cap values here:http://www.philcorepairbench.com/bblokcap.htm

[Chuck Schwark]

Early Tone Control cap values and wiring:

http://www.philcorepairbench.com/tonectl.htm

Schematic and/or parts listing will show embedded caps in later styles of tone controls.

[Guest]

Upon further investigation this set has one of the "later" tone controls, as it lists a .01 and a .015 capacitor as integral parts of the tone control circuit. Does this mean I need to pull the control and rebuild it like a bakelite block by removing the wax?

[Ron Ramirez]

Upon further investigation this set has one of the "later" tone controls, as it lists a .01 and a .015 capacitor as integral parts of the tone control circuit. Does this mean I need to pull the control and rebuild it like a bakelite block by removing the wax?

Yes.

I use hot glue to reseal the tone controls I rebuild, only to keep the capacitors in place. I do not reseal bakelite block caps when I rebuild them - there is no real need to do so.

[Chuck Schwark]

Be SURE to use 630 volt film caps. The working voltage must be high since the tone control is usually tied to the audio output plate. High DC voltage plus AC signal swings.

Chuck

[Guest]

This brings up a good question about the working voltage on the .0001 uf (Silver Mica replacements). The universal bakelite block description states 1200V! Do they need to be rated that high? It seems higher rated ones aren't easy to come by. Is 1000V enough, or 500/600V?

[mandh]

A rating of 500VDC for the silver mica caps is fine. The highest voltages in the radio are in the 300VDC range so there is no issue. I remember seeing a thread in the forum that said that the 1200VDC rating Philco used was a bit of overkill and the standard cap voltage ratings available today will work fine.

Harv, WA2AAE

[Chuck Schwark]

Early caps in the uuF (pF) ranges used relatively think dielectric, from what I understand. Wider "plate" spacing in a cap lowers the capacitance and raises the DC working voltage. High voltage caps were not needed in the original circuit designs, just worked out that way due to the construction practices and materials then in manufacturing caps.

Chuck