All tubes of a given type supplied with the equipment shall be consumed prior to employment of tubes from general stock.
If the tubes are ,good, connect the power to the chasis (with latter out of the case) and again move and tap the various parts and wires as a further means of ocating opens, shorts and grounds. Hum, squeals howls, distortion and other audible indications, dead voltage points, etc., may disclose the source of difficulty.
Failure of the quick check to disclose the source of the trouble should be followed by the reading of vohages at socket terminals and other points, continuity resistance measurements, realignment, signal tracing to isolate the faulty stages and replacement of major units as explained in succeeding paragraps.
b. SENSITIVITY.—The normal sensitivity (number of microvolts input to produce 10 milliwatts output into a 4,000 ohm resistance load) of the receiver is less lhan 3 microvolts (except on range 1, which is 5 microvolts) when measured as follows:
(1) With the AVC-OFF-MVC switch in the MVC position, the c-w oscillator OFF, the crystal filter OUT and a 4,000 ohm non-inductive resistance as the output
load feed a modulated signal from a signal generator into the receiver through a 100 mmf. dummy antenna. Adjust the output of the signal generator until the receiver output is 10 milliwatts. Turn off the signal generator modulation and adjust the receiver volume control until the noise output level is 2.5 milliwatts. Turn on the modulation and raise the signal generator output until the 10 milliwatt output is again indicated on the output meter.
(2) This svnsitivity will, of course, be subject to variation with time due to tube aging, etc. Therefore, it is recommended that no attempt be made to retrim or realign the equipment unless the sensitivity is found to be worse than 7 microvolts with new, average tubes
The receiver has been carefully adjusted and aligned by the manufacturer before shipment and should maintain
these adjustments over reasonably long periods of time.
Major adjustments and repairs should be made only in an authorized repair shop equipped with the necessary servicing tools and equipment. All others must refrain from changing any of tbe adjustments of the radio frequency circuits.
e. TROUBLE LOCATION AND CORRECTION PROCEDURE.—The following is a generalized trouble shooting procedure which may be used if no clue to