American Bosch 5 Schematic

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Product Information:
Manufacturer:American Bosch (United American Bosch & Fred M. Link)

Schematics Content:

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Model 5 Receiver

The readings were made with the volume control in the full "on" position.
* These voltages are the correct values. The average test kit will give much lower readings, (as low as 1/10 of these values) due to the low resistance of the meters compared to the thigh resistance included in the detector plate and screen circuits and the audio grid circuit.
When the volume control is reduced the
R.F. plate voltage remains constant
R.F. screen voltage increases
R.F. cathode voltage increases
R.F. grid voltage increases

Socket Voltages

Stage Tube Fil. Plate Screen Cathode Grid Plate M.A.
1st RF 224 2.3 250 90 2.5 2.5 4.5
2nd RF 224 2.3 250 90 2.5 2.5 4.5
Det. 224 2.3 *150 *20 3.0 1.5 .5
Audio 247 2.3 250 250 ... *16 32
Rect 280 4.8 Plate current of each plate - 20

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Cl - Antenna Trimmer Condenser
C2 - Tuning Condenser
C3 - Tuning Condenser
C4 - Tuning Condenser
C5 - Alignment Condenser
C6 - A1ignment Condenser
C7 - Coupling Capacity
C8 - Coupling Capacity
C9 - Audio Coupling Condenser .006 mfd.
C10 - Det. plate By-pass .0001 mfd.
Cll - RF Cathode By-pass .05 mfd.
C12 - RF Plate By-pass .05 mfd.
C13 - RF Screen By-pass .25 mfd.
C14 - RF Plate By-pass .05 mfd.
C15 - Det. Cathode By-pass 1.00 mfd.
C16 - Det. Screen By-pass .25 mfd.
C17 - Audio Grid By-pas .01 mfd.
C18 - Audio Plate By-pass .01 mfd.
C19 - Filter Condenser 4. mfd.
C20 - Field Condenser .08 mfd.
C21 - Filter Condenser 4. mfd.

Rl - Volume Control 10,000 ohms
R2 - RF Cathode Resistor 300 ohms
R3 - Det. Cathode Resistor 50,000 ohms
R4 - Det. Screen Resistor 2 megohms
R5 - Det. Plate Resistor 1 megohm
R6 - Audio Grid Resistor 1/2 megohm
R7 - Audio Grid Resistor 100,000 ohms
R8 - Mid Tap Resistor
R9 - Divider Resistor 50.000 ohms
R10 -Screen Resistor 50,000 ohms
R11 - Screen Resistor 10,000 ohms
R12 - Audio Bias Resistor 400 ohms

L1 - Antenna Coil
L2 - Primary of RF Coil
L3 - Secondary of RF Coil
L4 - Primary of RF Coil
L5 - Secondary of RF Coil
L6 - Speaker Moving Coil
L7 - Speaker Field Coil

T1 - Audio Output Transformer
T2 - Power Transformer

Filter Condenser
The three leads from the main filter condenser are connected as follows:
Black - to center tap of 280 plate winding
Green - to filament terminal oi 280 socket
Red - to +B connection on terminal strip

By-pass Condenser Assembly
The condensers incorporated in this unit are identified as follows:

1.0 mfd. Green Leads
.01 mfd. Green and White Leads
.05 mfd. Black Leads
.2S mfd. Red Leads

300 ohms - Orange, Black, Brown
400 ohms - Yellow, Black, Brown
10,000 ohms - Blue, Yellow
50,000 ohms - Green, White
100,000 ohms - Blue, White
1/2 megohm - Gray
1 megohm - Black
2 megohm - Black, White

Power Transformer
Six leads are brought out of the transformer winding on the side next to the terminal strip. Three are located on the opposite side. The transformer is connected as follows:

Primary Winding - Stranded wires, terminal strip side

224 and 247 filaments - Heavy wires, terminal strip side

280 filament - Small wires, terminal strip side

280 plates - Two leads nearest front of set, opposite side

280 center tap - Lead nearest back of set, opposite side

The trimmer condenser mounted on the loud speaker must be adjusted for maximum volume.

Some types of the 247 Pentode operate normally with a blue glow. This action does not, therefore, denote that the tube is defective due to gas.

It is very important that no tube is removed from its socket with the receiver "on" as to do this will damage the receiver or the Pentode tube.

Make sure that the lead from the top of each 224 tube to the variable condenser follows closely along the metal partition between the tubes. Oscillation may occur if this lead lies too close to the tube itself.

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