Tubes: 3-24, 4-27, 1-47, 1-80

The Philco Model 90 is one of the most famous, desirable, and widely recognized vintage radios of all times. The Model 90 cabinet was designed by Edward L. Combs and patented in February of 1931. The initial selling price of this radio when it debuted in June of 1931 was $69.95. This was considered by most as a substantial sum of money at the time.

The 1931 Philco Model 90 utilized a 9 tube Balanced Superheterodyne electronic design, which replaced the earlier designed TRF (tuned regenerative frequency) system. This new Superhetererodyne system was eventually adopted by all radio manufacturers.

The Model 90 utilizes 4 control knobs on the front.

The small knob in the center is a simple, 2 position on/off switch.

The medium sized knob to the left as you face the front is a 4 position tone, treble/bass control. This knob is turned to the to the left for more treble, and to the right for more bass. These tone settings were also called ("brilliant", "bright", "mellow" and "deep").

The large knob in the center is used to scan back and forth from one radio station to the next.

The medium sized knob to the far right is the volume control.

This Model 90 employees nine tubes.

The tube lineup is as follows: 24, 27, 24, 24, 27, 27, 80, 27, 47.

There were three different versions of the Philco Model 90 chassis electronics: an early, mid and late year chassis. This is a the mid version with a single 47 output tube, that was introduced in October of 1931. It has an automatic volume control (AVC) system. The AVC system would smooth out the signal strength between strong local stations and weak, hard to receive stations. The AVC system eliminated the harsh transition between stations that were experienced on earlier version radios of that era.

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