1. Introduction

The Philco Model 89 was in production for three and a half years (January 1933 through April 1936), and underwent a number of cabinet and circuit changes during this time period.

These circuit changes can be very confusing, especially since Philco only issued two Service Bulletins for this set, which do not cover all of the changes made to this model.

Before we begin to discuss the many circuit changes to Model 89, let’s take a look at the various cabinets this model was offered in.

Evolution of Philco Model 89 Cabinets

Model 89B, January 1933

Model 89L, January 1933

Model 89B, February 1933

Model 89B, March 1933

Model 89L, March 1933

Model 89B, 1935 (June 1934)

Model 89L, 1935 (June 1934)

Model 89F, 1936 (June 1935)

Model 89B, January 1936

2. Changes in Model 89 Circuitry

Model 89 sets with three knobs, receiving the AM band only, are all Code 121 sets. All Model 89 sets with four knobs, receiving AM and the “police” band (1.5 to around 3.3 mc) are Code 123, whether they use a 36 or 77 tube as the first detector and oscillator.

All of the documented changes made to Model 89 (along with a few undocumented changes) may be found in this thread, with accompanying schematics.

Click on any schematic below to see a larger image.

December 1932-January 1933:

Production of Model 89 begins. Introduced to the public January 1933. This is the original Model 89 schematic, as published in Service Bulletin 146 and in Rider’s Manual:

January 1933:

It is doubtful that any were actually produced with the tone control shown above. Most likely, all early Model 89 chassis used the tone control circuit as shown below.

Date unknown (possibly January-March 1933):

Resistor (42), part no. 4411 (99,000 ohms) changed to part no. 4409 (1 meg).

A .05 uF capacitor was added in parallel with the .09 uF section of capacitor (8 ). This capacitor was part no. 3615-L and was mounted between the antenna coil (2) and the RF tube socket.

3. Changes in Model 89 Circuitry, Continued

March 15, 1933: Code 121, Run 5.

Code 121 changed to Code 123.

Antenna coil (2) changed from part no. 06619 to 32-1062.

Detector transformer (6) changed from part no. 06662 to 32-1063.

Volume control and off-on switch, part no. 33-5004, changed to volume control only, part no. 33-5007.

Combined off-on and waveband switch added, part no. 42-1002.

Tuning condenser changed from part no. 06577 to 31-1010.

The above changes add a second band to Model 89, permitting police and airplace reception.

June 15, 1933:

Condenser (45), part no. 3615-E, changed to 3615-BF. This is a change in lug arrangement for mounting only.

No change in schematic.

October 15, 1933: Code 123, Run 3.

1st IF transformer (18 ) changed from part no. 06621 to 31-1289. Black and red leads to transformer reversed.

Resistor (48 ) changed from part no. 3525 (32,000 ohms) to 33-1027 (39,000 ohms).

Condenser (5), part no. 4989-W (.09 uF with 200 ohm resistor) changed to 4989-AG (.09 uF with 300 ohm resistor).

4. Changes in Model 89 Circuitry, Continued

November 15, 1933: Code 123, Run 5.

Tuning condenser changed from part no. 31-1010 to 31-1059.

No change in schematic.

November 15, 1933: Code 123, Run 7.

Type K-7 speaker changed to K-21. Condenser (45), 3615-BF, is now removed.

December 1, 1933: Code 123, Run 9.

Condenser 3615-L, .05 uF, formerly in parallel with .09 uF section of condenser (8 ), removed. Condenser (5), 4989-AG (.09 uF with 300 ohm resistor) removed. Above three parts replaced by condenser 4989-H (twin .09 uF) and flexible resistor 33-3010 (300 ohms) added from cathode of RF socket and ground.

5. Changes in Model 89 Circuitry, Continued

July 15, 1934: Code 123, Run 13.

Compensating condenser (15) changed from part no. 04000-M to 31-6024. New condenser is of improved design.

Resistor (10), part no. 6208 (15,000 ohms) changed to 4412 (10,000 ohms). Note that this change should be made to all earlier models of the 89 Series to improve oscillator performance.

September 1, 1934: Code 123, Run 14.

Type 77 detector-oscillator tube now used instead of type 36. This gives more stable results and requires the following changes:

Six-hole tube socket instead of five-hole.
Resistor (10) – (8 ) on new schematic below – part no. 6208 (10,000 ohms) changed to 33-1114 (8,000 ohms).
Condenser (8 ) – (9) on new schematic below – part no. 8174-B (.09 uF and 700 pF) changed to 8322-B (.05 uF and 1400 pF).

These changes prompted a new schematic which was not published until September 1935 (a year later)! See below:

The schematic as originally published in Service Bulletin 146-B and in Rider’s contained a few errors, which have been corrected above.

December 15, 1934: Code 123, Run 16.

Volume control, part no. 33-5007, and combined off-on and waveband switch, 42-1002, replaced by combined off-on switch and volume control, 33-5004, and waveband switch, 42-1040. This simplifies operation of the set.

6. Changes in Model 89 Circuitry, Conclusion

May 1, 1935:

Waveband switch, part no. 42-1040 changed to 42-1123.

No change in schematic.

June 15, 1935:

The following bakelite block condensers changed to new style (universal) condensers:

No change in schematic.

Unknown month and day, 1936:

Resistor (28 ), part no. 4409 (1 meg) changed to part no. 33-510344 (1 meg, 1/2 watt).
No change in schematic.