Porto-Server Inc. PB-520 Schematic

Porto-Server Inc. PB-520

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Product Information:
Manufacturer:Porto-Server Inc.

Schematic Pages

PNG: Page 1 Rider Manual Volume 15
PNG: Page 2 Rider Manual Volume 15

Schematics Content

Page 1:


Lettered terminals in illustrations correspond to simi. Early lettered terminals on the circuit diagram.

SOCKET VOLTAGES Measured with voltmeter having sensitivity of 1000 ohms per volt except where indicated by (*). VOLUME ON FULL WITH NO SIGNAL DIAL TUNED TO 540 KC.


Page 2:

Remove chassis and loop from cabinet. Reconnect both leads to loop and space it approximately same distance from chassis as when installed in cabinet With the gang condenser fully meshed, dial pointer should be in the position indicated by the last division below 55 on the dial. If it is set incorrectly, release pointer clip on dial cord and reposition pointer. Connect an output meter across the speaker voice coil or from the plate of the 50L6GT tube to chassis through a, 1 Mid. condenser, Connect the ground lead of the signal generator to the receiver chassis through a. 29 Mfd. condenser. Set volume control at maximum volume position and use a weak signal from the signal generator.

DIAL AND POINTER DRIVE CORD ARRANGEMENT To string dial cord, set gang condenser to fully meshed position and use following parts:
114955 Clip on end of cord
117057 Cord (26 inches)
119087 Ring for dial cord
161284 Tension Spring


Be sure R.F. and I.F. stages are accurately aligned before measuring gain. R.F. gains can be measured with a " channel " type instrument containing atuned 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 shown. Use 600 KC signal with 400 cycles modulation (use nearby frequency if local station interferes.)

2. For R.F. and I.F. measurements connect negative terminal of a 3 - volt battery (two 12 volt cells 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 signal for sharp tuning.)

4. When using a " channel " type instrument carefully tune it for maximum out put 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 capability 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.