Porto-Products, Inc. PB-520 Schematic

Porto-Products, Inc. PB-520

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Product Information:
Manufacturer:Porto-Products, Inc.

Schematic Pages

PNG: Page 1 Rider Manual Volume 18
PNG: Page 2 Rider Manual Volume 18

Schematics Content

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APPROXIMATE STAGE GAIN DATA Be sure R.F. and I.F, stages are accurately aligned before measur. ing gain. R.F. gains can be measured with a " channel " type instrument containing a tuned and calibrated R.F. amplifier. A vacuum tube voltmeter may be used for audio gain measurements. Observe following precautions:

1. For all gain measurements connect signal generator as shown. Use 600 KC signal with 400 cycles modulation (use nearby frequency it local station interferes.)

2. For R.F. md I.F. measurements connect negative terminal of a 3 - volt battery (two 12 volt cehs in series) to A.V.C. lead and positive terminal to chassis. This provides a definite operating point.

3. Be sure radio is carefully tuned to generator signal (use weak sigaal for sharp tuning.)
4. When using a " channel " type instrument carefully tune maximum output at desired frequency before making measurements.
The R.F. and I.F. stage gains shown below are less than under normal operating conditions due to the use of 3 volts fixed bias in order to establish a definite operating point. Therefore, these values are not intended to indicate the full capacity of a stage.
Differences in tube characteristics, tolerance of parts, adjustment of tuned circuits, and variations of line voltage will influence stage gain. Accuracy of measurements is dependent upon careful tuning of receiver to generator signal and experience in using your test equipment. These factors may create considerable variation in gain measurements.

1. Remove chassis and loop from cabinet.

2. With the gang condenser fully meshed, dial pointer should be in the position indicated by the last division below 55 on the dial. It it is set incorrectly, release pointer clip on dial and reposition pointer.

3. Connect an output meer across the speaker voice coil or from the plate of the 50L6GT tube to chassis through a. 1 Mfd. condenser.

4. Connect the ground lead of the signal generator to the receiver chassis through a. 25 Mid. con denser,

5. Set volume control at maximum volume position and use a weak signal from the signal generator.

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