Pure Oil Corp. 506
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|Manufacturer:||Pure Oil Corp.|
Measured with voltmeter having sensitivity of 1000 ohms per volt except where indicated by (*).
The audio system of this receiver utilizes a two stage type of inter feed-back arrangement and should it ever be necessary to replace the speaker or output transformer, it is important to maintain a definite phase relationship in the feed-back circuit. I the connections to the output transformer are reversed or if the feed-back connection is made to the wrong side of the output transformer secondary, the system will become regenerative instead of degenerative. Under those conditions audio oscillation may result. If that occurs, sscillation may be prevented by reversing the connections to the secondary of the output transformer.
1. Remove chassis and loop from cabinet. Solder approximately 8" of insulated wire to any B connection (800 voltage chart on opposite side of convenient Ben location). Then reinstall chassis and loop in cabinet. The B - lead should extend from under the chassis at the back.
2. Connect ground lead of signal generator to B lead.
3. Connect output meter across the speaker voice coil (terminals at back of speaker.)
4. Turn the tuning control knob clockwise as far as it will go (tuner mechanism is now in maximum open position with tuning slugs almost completely withdrawn from coils). Dial pointer should then point to 1600 Kc mark on scale. If it is set incorrectly, release pointer clip on dial cord and reposition pointer.
5. Set volume control at maximum volume position and use a weak signal from the signal generator.
APPROXIMATE STAGE GAIN DATA
Be sure A.F. and I.F. stages are accurately aligned before measuring 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. Vse 600 KC. signal with 400 cycle 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 14 volt cells in series) to A.V.C. lead and positive terminal to B- This provides o definite operating point.
IMPORTANT: Disconnect battery when measuring audio stage gains.
3. Be sure radio is carefully tuned to generator signal (use weak signal for shop tuning.)
When using a "channel" type instrument carefully tune it for 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, those values are not intended to indicate the full capability of a stage.
Differences in tube characteristics, tolerance of parts, adjustment of tuned drcults, and variations of lin. 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.