Jackson Bell Co., Ltd. 60 Schematic

Jackson Bell Co., Ltd. 60

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Product Information:
Model:60
Manufacturer:Jackson Bell Co., Ltd.

Schematic Pages

PNG: Page 1 Rider Manual Volume 7
PNG: Page 2 Rider Manual Volume 7

Schematics Content

Page 1:

MODEL 59 - JACKSON - BELL RECEIVER
This is a tuned radio frequency circuit, using 26 tubes as radio frequency amplifiers, grid leak detector, using a 27 tube; two stages of audio, transformer coupled; 26 in first stage and two 71's in push-pull in the last stage and a full wave rectifier. Volume is controlled by variable R.F. bias and antenna shunt.

Page 2:

VOLTAGE AND CURRENT VALUES MODEL 60 RECEIVERS
The following values are correct with 1000 ohm speaker field and 110 volts A.C. on the line, or 125 volts on the line when power transformer is the connected. Witb volume control at half way position the following voltages should be indicated from ground:

CONTINUITY TESTS:
The following resistance values should be observed when making continuity tests without removing the chassis from the cabinet:

COILS:
Effective immediately, specifications of the radio frequency transformers used in the model 60 receiver are changed to the following:
Primaries ... 16 turns
Secondaries ... 81 "
Circuit Inductance ... 240 microhenries
The overall gain throughout the radio frequency amplifier with the new coils 16 approximately 300 % greater than with the old ones. The substantial increase of sosi tivity should, therefore, be observed.
When orders for replacement coils are filled they will always be in complete sets of three and of new type.

GRID SUPPRESSORS
Service notes and circuit print of this receiver snow 2 800 ohm grid suppressors. The grid suppressor of the first radio frequency stage has been reduced to 300 ohms. The second one remains 800.

FILTER SYSTEM
Specifications of this receiver call for 2 - 8 microfarad electrolytic condensers in the filter, At times when the factory has been unable to obtain these electrolytic condensers it has been necessary to substitute paper condensers and an additional filter choke. The value of the units in the paper condenser block is as follows:
When the block is fastened in the chassis and the chassis is viewed in an inverted position, the bottom terminal is five microfarads, the center terminal one microfarad and the top terminal two microfarads. Only a limited number of these have been installed and regular production will continue to contain the electrolytic condensers.

MODEL 62 2nd & 3rd Series

SERVICE NOTES FOR SERIAL NO. 120,000 AND UP
If it should become necessary to resonate the radio frequency circuit, proceed as follows:
Set the dial at about 20 degrees and set all coupling condensers at approximately one full turn to the left of the maximum capacity adjustment. with a grid dip oscillator, check all circuits for resonance, making connection to the cape on top of the screen grid tubes. The tubes should be cold when this is done. If it is necessary to move any of the coupling condensers more than one-half turn in order to obtain resonance, adjustment of capacity in that particular stage should be made by bonding the split rotor plate of the variable condenser. This does not apply to the antenna stage where the condenser on the coil does not affect coupling. When resonance has been obtained at this point, the dial should be shifted to 90, and all stages again checked with a grid dip meter. Here all capacity adjustments must be made by bending plates, being careful not to disturb the position of that portion of the split plate which was active when the first adjustment was made.

VOLTAGE AND CURRENT VALUES
With the volume control at maximum, the following readings should be obtained, with an allowable variation of 10 %

* This reading will be obtained with a 300,000 om volt-meter as found in a Jewell 199 test set. This reading is subject to considerable variation with meters of various resistances, as the voltage at this point is measured through a 500,000 ohm resistor. The voltage at the opposite end of the resistor should be 250.

MODEL 68
If it should become necessary to resonate the radio frequency circuit, proceed as follows:
Set the dial at about 20 degrees and set all coupling condensers at approximately one full turn to the left of the maximum capacity adjustment. With the grid dip oscillator, check all circuits for resonance, making connection to the caps on top of the screen grid tubes. The tubes should be cold when this is done. If it is necessary to move any of the coupling condensers more than one-half turn in order to obtain resonance, adjustment of capacity in that particular stage should be made by bending the split rotor plate of the variable condenser. This does not apply to the antenna stage where the variable condenser on the coil does not affect coupling. When resonance has been obtained at this point, the dial should be shifted to 90 and all stages again checked with the grid dip meter. Here all capacity adjustments must be made by bending plates, being careful not to disturb the position of that portion of the split plate which was active when the first adjustment was made.