Philco Model 66 Restoration

The Philco Model 66  is a 5-tube AC superhet circuit radio.  It receives the standard broadcast band and one short wave band.  The circuit is conventional, but the cabinet design is bold and quite deco!  The radio had seen minimal servicing in the past and had not been hacked excessively.  This being the case, I decided to try and retain the original top and bottom chassis appearance if possible.  Previous servicing included several replacement tubes (I assume all original tubes would have been Philco branded), a replacement volume control (of the incorrect resistance), a tacked in electrolytic capacitor, and one tubular capacitor (part 27). The schematic for the Philco 66 can be found on Nostalgia Air.  Any part numbers will refer to numbers on that schematic.

My antique radio restoration logs

Survey

My usual restoration procedure is to first make a complete survey of the condition of all components.  The survey results guide my restoration strategy.  If major and unique components are defective and cannot be restored, I may elect to sell the radio rather than restore it.  I assume that all paper and electrolytic capacitors are leaky and thus should be replaced (I always "restuff" the original containers if possible).

• There was one tacked in filter across the input filter (part 50).

• Capacitor 27 had been replaced.

• The volume control (part 39) had been replaced by a 20K pot!  I don't think the radio would have worked very well - the correct resistance was 350K.

• The AC switch was bad - open..

• The AC line cord was original but had several bad places - it was very stiff in spots.

• Two tubes were bad - 80 (intermittent filament) and 75 (very weak).

• The rubber grommets supporting the tuning capacitor were stiff and had shrunk - there was too much play.

• The chassis washers were stiff and had shrunk.  All chassis bolts and washers were present.

• All coils, transformers, and the filter choke were OK.

• The speaker field and cone were OK.

• Nine resistors were out of tolerance by 36% to 95% (dogbone types).

• The wire wound resistor 44 was fortunately good - bias resistor.

Repairs

Here's a hint for anyone restoring this radio.  Many components are mounted on a terminal board.  this board must be removed in order to properly replace components.  It also blocks access to wiring and some components below it.  So my suggestion is to carefully tag all wires, take good notes, and remove the terminal board first thing!

All paper and bakelite block capacitors were rebuilt in their original cases using modern 630 volt film capacitors in order to maintain the original under-chassis appearance.  One non-original capacitor (part 27) was replaced by a Philco tubular capacitor that was restuffed (unfortunately I did not have an original Philco capacitor of the correct value - .1uf).  

The two can type electrolytic capacitors were also rebuilt in their original containers.  The cans were scored on a Unimat lathe and the cut completed using a hobby razor saw.  The cuts were near the base in both cases so that the joint would be hidden by the clamps or insulating cover.  The original contents were removed, the cases cleaned, new 450 volt electrolytics installed inside, and the two halves of the cans joined using PVC plumbing couplings and epoxy.  The single capacitor (part 49) was originally 6uf at 475 volts.  The dual capacitor (part 50) was 2 x 8uf at 450 volts.  I used 10uf at 450 volts for all of them.

All original resistors more than 20% out of tolerance were replaced.  I used dogbone type resistors as were used originally.  I picked out NOS and used dogbone resistors that had the correct resistance and then repainted them to match the original resistor's color codes.  The replacements had also drifted in value, and may continue to drift, as would most new carbon composition type resistors.  But to me, maintaining the original look is more important than long term reliability of the radio.

The capacitors inside the tone switch were replaced, and the switch filled with rosin (the original was filled with tar).

Volume Control

The original AC switch on the volume control was bad.  However the volume control had been replaced by a 20K pot with switch.  I was fortunate to find an original Philco volume control in my junk box that was good.  The original control in the radio was Philco part 33-5006.  I replaced it with a Philco part 33-5306-2.  It had the same resistance as the original as well as the same shaft length and appearance!  A real lucky find!  The only problem was that the flat on the shaft was too deep for the original knob (meant for a different type of knob).  This was fixed using a cardboard shim in the knob.

Other Repairs

• The original line cord had several places where it had broken, and was stiff in spots.  I was able to cut it at a couple of breaks and splice it back together (using shrink tubing to cover the splice). I was able to salvage about 4 feet of the original cord, as well as the original plug.
• The tuning capacitor grommets were replaced.  This eliminated the play in the tuning capacitor.  These grommets are available from Renovated Radios, part GLg-Tuner.
• The chassis was cleaned using GoJo and steel wool, tooth brushes, small bottle brushes, and pipe cleaners.
• The bandswitch was cleaned using lacquer thinner and Big Bath spray cleaner.

Testing and Alignment

Once the radio was reassembled and tubes installed, power was brought up slowly using a variac.  AC power was monitored using a watt meter, and a DVM monitored the B+.  The radio came alive immediately and worked.  Once at full power, voltage measurements were taken.  

The set was aligned - no surprises.  One of the IF trimmers was way off - the rest were close.  The oscillator, RF, and low-frequency padder peaked up nicely.

Restoration Results

Chassis Before Restoration	Chassis After Restoration