Philco Radio













Radio Manufacturers Service. Your Guarantee of Best Radio Service

MODELS 20, 21, 70 and 90 FROM 1931-1933


Excerpted from articles which appeared in the August, 1993, July, 1994, May, 1995
and July, 1995 issues with permission of Antique Radio Classified and the authors.
© Copyright 1993, 1994, 1995 ARC, Ron Boucher and Ron Ramirez.

Fig. 1 Philco Model 20 Fig. 2 Philco Model 20 Deluxe Fig. 3 Philco Model 70 Fig. 4 Philco Model 90
Model 20
Fig. 1
Model 20 Deluxe
Fig. 2
Model 70
Fig. 3
Model 90
Fig. 4

Serial Numbers and Dates   The serial number can help date your radio. The equipment that Philco used for stamping serial numbers was capable of stamping six digits. This meant Philco could go up to 999,999 using only digits, but in the 1931 model year, higher serial numbers were required. What the company did was to use the letter "A" instead of "10" for the first digit, and "B" instead of "11". The next number after 999,999 was A00000, which corresponded to (10)00000 (another example: B22000 = 1122000).

   Since many of the cabinets have dates rubber-stamped on the bottom of the cabinet, we have a chance of correlating the date, serial number, and features to find out when these changes occurred. The survey results, as of July, 1995, are shown in the accompanying graphs and charts. The charts will allow you to pinpoint when a particular radio was made from the serial number or other features, even if that radio had no date stamp.

   Knowing that the cabinets were not made in the same area of the factory as the chassis, we realize that the serial numbers on the chassis and the date stamps on the cabinets might not correlate one hundred percent, but we think sufficient responses to this survey should help make sense of the numbers. It is important to note if you have any doubts that the chassis came originally with the cabinet.

   If you would like to include the data from early Philco sets you may have in your collection, use the authors' Survey Form. Explainations for the survey questions are belown to help you with your answers.

Data Guide Explanation   Since there are many variations in the models being surveyed, even experienced collectors sometimes have difficulty making proper identification. The Data Guide in Table 1 below, is intended to aid those who may have only one set and no others with which to compare it. They can now identify their models more easily and provide the information we request.

Model   This column lists the models included in the survey. Note that Model 21 has an "early", "late", and "very late" version with chassis variations.

Serial Number   Please enter the serial number for each of your radios.

Cabinet Type / Decal   Please indicate which cabinet style your set has (see Figs. 1 - 4 above). For Model 20, also indicate whether the cabinet is "plain" or "deluxe". Also please note any cabinet variations in the other models and indicate if your radio has a patent design decal on the rear arch of the cabinet (see Fig. 6).

Knobs   This column identifies two different knob styles commonly referred to as "plain" or "rosette", as shown here in Figure 5. Please indicate if the knob style listed does not agree with the knobs on your set(s).

Fig. 5 - Knob Styles
Plain         Fig. 5         Rosette

AVC   Model 70 sets without Type 35 tubes do not have AVC (Automatic Volume Control). For Model 90, if the set has the "Normal-Maximum" toggle switch on the back of the chassis, it does not have AVC.

Date of Manufacture   Look for a date stamp, usually rubber-stamped on the bottom of the cabinet, and enter the date in this column. Note: Models 70 and 90 show different manufacturing periods for the same model number, so be sure to check the date of manufacture of your set against the data given.

Fig. 6 - Set Markings
Fig. 6. Decal (top), model number (lower right), and serial number (lower left) locations.

Switch   Some Model 90 sets have a "Normal-Maximum" switch on the rear of the chassis and some do not. Check your set for the presence of this switch.

Escutcheon   If you have a Model 70, does it have a metal or Bakelite escutcheon? The escutcheon is the ornamental plate surrounding the tuning dial scale.

Tubes   The number of tubes and tube types is very important. Carefully check the tube compliment of your set against the tube compliments shown in the these diagrams. Be sure also to check Table 1 for the tube types and quantity for the model chassis in your radio. Note: Your set may have other substitute (or wrong types) tube types installed from a previous repair job!

Tube Layout - Models 20/21          Tube Layout - Model 70 Early and Late

Tube Layout - Early/Mid Model 90          Tube Layout - Late Model 90

Trimmers   If you have a Model 20, note that a chassis can have 1, 2, or 3 trimmer condensers. These trimmers" are screw-type adjustments are usually mounted on the variable tuning capacitors. Please indicate whether your set has 1, 2, or 3 trimmers.

Comments   A remarks line is provided at the bottom of the form. Please add any comments that may be helpful.

Table 1. Philco Cathedral Model Data Guide
Philco Model Early, mid-, late
or very late
AVC Norm.-
No. of Tubes-
20 --- Plain or Deluxe Plain No No Metal 3-24, 1-27, 2-71A, 1-80 1, 2 or 3
21 Early (has Mod. 20 chassis) Same as Model 70 Plain No No Metal Same as Mod. 20 3
21 Late (has Mod. 21 chassis) Same as Model 70 Rosette No No Metal Same as Mod. 20 3
21 Very late (has Mod. 21 chassis) Same as Model 70 Rosette No No Metal 3-24, 1-27, 2-45, 1-80 3
70 Early, 6/'31 to 12/'31
(Below Serial # B-22,000)
--- Rosette No No Metal or Bakelite 4-24, 1-27, 1-47, 1-80 3
70 Late, 1/'32 to 5/'32
(Above Serial # B-22,000)
--- Rosette Yes No Metal or Bakelite 3-35, 1-24, 1-27, 1-47, 1-80 3
90 Early, 6/'31 to 9/'31
(Below Serial # 237,000)
--- Rosette No Yes Metal 4-24, 2-27, 2-45, 1-80 4
90 Mid-, 10/'31 to 12/'31
(Above Serial # 237,000)
--- Rosette Yes No Metal
(early runs)
3-24, 4-27, 1-47, 1-80 4
90 Late, 1/'32 to 5/'32
(Serial #s B-32,001 to B-35,000
and above Serial # B-53,100)
--- Rosette Yes No Bakelite 1-24, 3-27, 2-35, 2-47, 1-80 4


Deco Corner


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