The Philco Model 41 Receiver is a direct current (DC) radio designed for operation within a voltage range of 100-130 volts. It is crucial that this receiver is not connected to an alternating current (AC) line, as it is specifically engineered for DC power.

Function Description:

The Model 41 Receiver is a radio designed to receive broadcast signals. Its internal circuitry includes multiple stages of radio frequency (RF) amplification, an intermediate frequency (IF) stage (implied by the presence of RF transformers and detector), an audio frequency (AF) amplification stage, and a detector to convert the radio signal into an audible output. The receiver utilizes a series of vacuum tubes, specifically 24s, 27s, and 71-As, for its various amplification and detection functions. A volume control allows the user to adjust the output level, while a tone control provides adjustment over the audio characteristics. A station selector enables tuning to different broadcast frequencies. The receiver also features an on-off switch for power control.

Important Technical Specifications:

Tube Socket Readings (Line Voltage 115):

These readings are critical for troubleshooting and understanding the operational parameters of each tube. All readings should be taken with the volume control set to full. A high-resistance voltmeter (preferably 1000 ohms per volt or higher) is recommended for accurate measurements, especially for plate and screen voltages, which should be read on a 250- or 300-volt scale. Using meters with less than 250,000 ohms resistance will result in lower voltage readings than those specified.

Tube 24 (1st R.F.):
- Filament: 2.1
- Plate: 100
- Screen Grid: 75
- Control Grid: .4
- Plate Mils: 2.7
Tube 24 (2nd R.F.):
- Filament: 2.1
- Plate: 100
- Screen Grid: 75
- Control Grid: .4
- Plate Mils: 2.7
Tube 24 (Detector):
- Filament: 2.1
- Plate: 45
- Screen Grid: 15
- Control Grid: 1.8
- Plate Mils: (Not specified, likely very low or not applicable for this measurement)
Tube 27 (1st A.F.):
- Filament: 2.4
- Plate: 87
- Screen Grid: (Not specified, likely triode)
- Control Grid: .2
- Plate Mils: 2.7
Tube 71-A (2nd A.F.):
- Filament: 5
- Plate: 85
- Screen Grid: 13
- Control Grid: (Not specified, likely triode)
- Plate Mils: 15
Tube 71-A (2nd A.F.):
- Filament: 5
- Plate: 85
- Screen Grid: 13
- Control Grid: (Not specified, likely triode)
- Plate Mils: 15

Resistor Values:

These values are crucial for maintaining proper voltage division and current limiting within the circuit.

5,000 Ohms (No. 17, 36)
13,000 Ohms (No. 23)
25,000 Ohms (No. 19, 34)
33,000 Ohms (No. 7, 13)
70,000 Ohms (No. 24)
100,000 Ohms (No. 20, 26)
500,000 Ohms (No. 25, 28)
250 Ohms (No. 33)
4 Ohms (No. 37, Terminals 1-2)
2 Ohms (No. 37, Terminals 2-3)
53 Ohms (No. 38, 20-inch - External)

Condenser Capacities (Other than Filter Condenser):

These capacitors are essential for filtering, coupling, and tuning within the receiver.

.01 MFD (No. 27)
.05 MFD (No. 6, 12, 16, 18)
.25 MFD (No. 9, 22, 21)
.0005 MFD (No. 32)
Filter Condenser: Part No. 4067

Usage Features:

The Model 41 Receiver is designed for straightforward operation. The user interacts with the volume control, tone control, station selector, and on-off switch. The resistor plug, which is located in the socket at the rear right-hand corner of the base, is intended for use in some AC models with an 80 rectifier tube. However, for this DC receiver, no rectifier is required, and placing a tube in this socket will not cause damage.

Maintenance Features:

General Information:

Power Source: Strictly 100-130 volts DC. Connecting to AC will damage the unit.
Resistor Plug: The resistor plug must be correctly placed in the designated socket. This socket is typically for an 80 rectifier tube in AC models. For the DC Model 41, no rectifier is needed, and inserting a tube here will not cause damage.
Speaker Compatibility: The speaker's field coil has low resistance and is specific to this DC model.
- AC Speaker on DC Receiver: Plugging a speaker from an AC Electric Receiver into the DC Model 41 will not cause damage, but the signal will be extremely weak and distorted.
- DC Speaker on AC Receiver: Plugging a speaker from a DC Electric Receiver into an AC Receiver will not cause damage, but reception will be weak and distorted.

Compensating (Alignment) Procedure:

This procedure is critical for optimal receiver performance and involves adjusting the compensating condensers.

Preparation: Always use an oscillator signal. Set up the receiver for operation and tune the oscillator and receiver so the signal is between 120 and 140 on the tuning scale. Turn the receiver's volume control to full. Adjust the oscillator so the received signal is very weak.
First Stage Adjustment: Using a fiber wrench, turn down the adjusting nut of the first compensating condenser until it is quite tight. This action intentionally throws the first stage out of balance to facilitate the second stage adjustment.
Second Stage Adjustment: After tightening the first adjusting nut, compensate the second condenser. Carefully tune the receiver to the oscillator signal and adjust the second compensating condenser for the maximum signal.
Final First Stage Adjustment: Once the second stage is adjusted, proceed to adjust the first compensating condenser in the same manner (tuning for maximum signal).

Replacement Parts:

A comprehensive list of replacement parts is provided, including their descriptions and Philco part numbers. This list is invaluable for repairs and maintenance, ensuring that correct components are used. Examples include:

Volume Control (Part No. 4094)
First R.F. Transformer (Part No. 3884-A)
Tuning Condenser (Part No. 4069-E)
Compensating Condenser (Part No. 3772-A)
Choke (Part No. 3422)
Output Transformer (Part No. 2848)
Voice Coil and Cone (Part No. 2814-B)
Field Coil (Part No. 2799)
Pilot Lamp (Part No. 3463)
Various resistors, capacitors, knobs, clips, shields, washers, and sockets.

This detailed information ensures that technicians and users can effectively operate, troubleshoot, and maintain the Philco Model 41 Receiver for optimal performance and longevity.

Philco 41 - Page 3

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