Philco 20

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This Philco 20 must have manage to irritate the owners dog one day. So it took a chunk out of the grill lattice work.	The flash brought out the wrinkle in the grill cloth and illuminated the backing board. these are not visible with out a flash.	There are multiple layers of lacquer and hand rubbed paste wax.	Nice interior shot. Don't worry. My repair sticker is on a magnetic sticky card.
Before	After

Philco Model 20 (1934 vintage) is a TRF (not superhetrodyne) radio. It has all tuned circuits to receive and detect the audio from the air. Here are some pictures of the restoration.

Electronic Restoration

The only restoration challenge is restuffling the large multi section capacitor. There in which the real challenge is minimizing the melted tar or pitch. I held the capacitor in front of a LP space heater and kept it moving. Softening of a layer that contacts the inside of the can is the goal.

I removed this capacitor from the chassis. I was later told this is unnecessary. You only have to unbolt the retaining screws and pull up on the can while gently restraining the bottom cover. It separates. The bottom is not affixed to the upper can. Then clip the wires, clean out the can and add new capacitors.

The smallest electrolytic that I had on hand was 10 uf. They work fine. 10 uf is well with in the capacitor specifications of the #80 rectifier tube (I always check). I used a Polypropylene 0.1 uf 630 volt as well for a direct value replacement of .13 uf across the choke. Riders Vol 2 page 2-3,4 Vol 1-6 from Nostalgiair.org


This radio seems to have been stored near a coal shed. Typical seventy years of dirt.		Bottom view of multi section can capacitor.
	A fully restored, operational chassis!

Resistors

I found all but two resistors out of tolerance. Most beyond 100%. I replaced the resistors with two 1/2 watt in parallel to obtain 1 watt dissipation. Of course the individual resistors wattage are double the needed value. I have saved the original resistors in the event that someone would later intend to make reproduction "dog bone" resistors to maintain the vintage look.

And how about those Dog gone Dog Bone Resistors? Try Syl's web site.

Bakelite Capacitors

After removal, clip the lead wires exiting the rivets, heat with a 40 watt focused spot light, and push the insides out with a small stick through a rivet. I have broken a case before, by using a screw driver.

Clean with contact cleaner and solder in new caps. Season to taste and Replace. Check your schematic or see, http://www.philcorepairbench.com/partinfo.htm and select the Bakelite Blocks for what is inside. Thanks to the Philco Repair Bench for maintaining such a valuable Resource!

Alignment

Alignment is simply putting the RF generator on 1400 khz, setting the dial on 140 (1400 khz), placing a loop of wire near the antenna (a length of wire) and adjusting the three compensating capacitors mounted on the variable air capacitor. Some models only have one or two.

If tracking is off, bending of the outer most disc of the air capacitor is needed. This radio tracks accurately. No adjusting is needed. However, several, not all, bent plate sections were apparent on the center section rotor.

Cabinet

Before stripping. This is the condition as originally found. Normally I try to save the original finish. But as you see there was little to salvage. This radio was destined for the dumpster.	New arch added. Veneer, removed from under a trim strip did not match. A new piece of wood backed veneer was used in the final repair. It was quite hard to color match this new veneer.
After stripping. If you look close the toned wood filler can be seen. It is not as red in sunlight and interior lights. The camera's flash seems to bring out the Red tone of the filler.	Finished radio. The tinted wood filler takes the color matching markers well. Better than stain. The Tan knob felts have been changed to Dark Brown. They no longer contrast with the finish.

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