07-04-2006, 08:34 PM
AI2V Wrote:Gary is right-on; those 6 or 7 tar blocks need to be emptied and recapped. When you get good it will only take less than 2 minutes to remove and gut one.
First scribble a drawing of your first block and what goes to each of the three terminal strips; unsolder the wires and resistors (an excellent time to measure the resistors when one lead is not connected); remove the block and heat with a heat gun until the tar just starts to soften/liquify around the edges; using a small screwdriver, dig off the first 1/8 inch of tar (should expose the caps); now carefully pry out the caps. When the caps are out and the block scraped out, push a drill bit through each of terminal holes to clear out the old leads. At this point you are ready to clean off the block (acetone), remove the excess solder and broken leads from the terminals, and install the new caps. The values in these blocks are very UN-critical with the exception of the 110uuf (I use 120uuf) in the detector stage. When doing Philco's, you've got to learn the process and this is one step that cannot be skipped.
I just did my first rebuilding of a bakelite block capacitor. This is almost easier than it sounds. The inner portion only contained one .01 mfd cap and was relatively easy to stuff inside the housing. After doing a few of these, the radio's audio shows signs of improvement. There's alot more to go.
One question on this subject though. Is it necessary to restuff the bakelite blocks with a material simular to the tar that was inside it prior to removal? I've heard that it's almost not worth the effort. With no insulation the newly installed cap itself will far outlast what used to be in there. Comments? Suggestions?
73 de,
Gary/N9VU