Jackson Bell Co., Ltd. 87 Schematic

Jackson Bell Co., Ltd. 87

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Product Information:
Model:87
Manufacturer:Jackson Bell Co., Ltd.

Schematic Pages

PNG: Page 1 Rider Manual Volume 6

Schematics Content

Page 1:

CIRCUIT ALIGNMENT:

The first stop in alignment of the receiver is to align the intermediate amplifier. This must be done with a test oscillator set at exactly 175 kilocycles, and an output indicating device. Remove the oscillator tube from the receiver and connect the test oscillator to the grid of the first detector tube. The trimming condensers for the intermediate circuit are adjusted by means of the screws accessible thru the holes in the sides of the intermediate transformer shield covers. The volume control should be in the maximum or full-on position. Rotate the adjusting screws until maximum response is shown in the output meter.

ALIGNMENT OF THE SIGNAL FREQUENCY CIRCUIT

For this operation, a modulated test oscillator covering the broadcast band is required, or stations of known frequency may be used. In order to properly resonate the signal frequency circuit of this receiver, turn the dial to some known frequency on the high end of the band, adjust the oscillator trimming condenser of the tuning condenser, until the greatest response is shown in the output meter. Then adjust the first detector section and next the first R.F. circuit section of the tuning condenser. Now move up to the next known frequency, preferably located at the next split section of the condenser. The alignment from here on is accomplished by bending the split sections of the condenser plates to give the maximum alignment indicated by the output meter. If condenser plates have to be ben apparently too much at the low end of the band, it is advisable to start at the beginning and compensate the difference by bending the plates on the high frequency end. Or, also by shifting the dial and re-aligning so as to eliminate unnecessary bending of the plates to get the proper alignment. It is not advisable to bend the plates in, especially in the oscillator section, as this may cause a microphonic howl in the receiver due to the vibration of these plates if too close together.

AVERAGE VOLTAGES & CURRENTS: