CHASSIS NO. 20,21 AND 23

All the circuits in this receiver are very accurately adjusted at the factory and normally should need no fur. ther adjustment. However, if it is definitely known that an adjustment is necessary the circuits may be properly aligned with the use of a modulated signal generator and an output meter.
CONNECTING OUTPUT METER Connect the output meter to the plate and screen of the GKG output tube. Be certain that the meter is protected from D.C. by connecting a condenser (. 1 mld. or larger not electrolytic in series with one of the leads. Tuning I - F Amplifier To 455 Kilocycles,
(a) Connect the output of the signal generator through a. 02 md. condenser to the antenna lead (Blue). Connect the ground lead from the signal generator to the ground lead (Black) of the receiver,
b) Set the station selector so that the tuning con deuser plates are completely out of mesh. Turn the volume control knob to the right (ON).
10) Turn the band selector switch to the Broadcast Band. (Left). Push switch on loop ant. to B.C. posi. tion.
(d) Set the signal generator to 455 kilocycles.
(e) Adjust both trimmers located on top of the 2nd 1 - F transformer for maximum output.
(f): Adjust both trimmers located on top of the 1st I.F transformer for maximum output.
(g). Check operations (e) and (f) for more accurate adjustments.
ALWAYS USE THE LOWEST SIGNAL GENERA TOR OUTPUT THAT WILL GIVE A REASONABLE READING ON THE OUTPUT METER. Aligning The R. - F Circuits.
(1) Connect the signal generator output through a 400 ohm carbon resistor to the antenna lead (Blue) of the receiver and the generator return to the ground lead (Black),
(a) Set signal generator to 15.4 megacycles.
ibi Open tuning condenser all the way (rotor completely out of mesh) turn band switch to the right,
short wave) and volume on full. On models 21 and 23 turn tone control to treble position.
(c) Adjust the S.W. " OSC " trimmer, located on gang condenser, for maximum output.
(d) Set signal generator to 15.0 megacycles.
le) Tune-in signal generator frequency with the sta. tion selector knob (approximately 15 on the dial) and while slowly rocking the station selector knob adjust the S.W. " ANT. trimmer condenser, center trimmer on right end of chassis, for maximum output.
NOTE: Check the image frequency by increasing the signal generator output. Tune-in 15 mc. signal and then the image which should come in around 14 on the dial. If image is not heard the oscillator is aligned on the wrong peak and S.W. " OSC " trimmer should be

Further opened until correct peak is found.
(f) Repeat (a) to (e) for more accurate adjustments.
(2) Change the 400 ohm dummy antenna to a. 0002 ml. (200 mmf.) condenser. Turn band switch to B.C. position (left), open gang condenser all the way, etc.
(a) Set signal generator to 1650 kilocycles.
(b)'Adjust the B.C. " OSC " trimmer for maximum output (front trimmer, right end of chassis).
(c) Set signal generator to 1400 kilocycles.
(d) Tune-in 1400 kc. signal with tuning condenser, (should be approximately 14 on the dial), then adjust the B.C. " ANT " trimmer (rear trimmer, right end of chassis) for maximum output.
(e) Repeat (a) to d) for more accurate adjust. ments.
(3.) Ueing same dummy antenna (. 0001 mf.) align the Special Police Band antenna trimmer (there is no oscillator adjustment for this band)
(a) Set signal generator to 2.5 kilocycles.
(b) Push switch on loop antenna to Pol. position and then tune in the generator signal with gang, approx. 2.5 on the dial.
(c) Adjust trimmer on loop antenna for maximum output.
CAUTION: Be sure to push the switch on the loop antenna back to B.C. position if receiver is to be used for broadcast receplion.
WAVE TRAP Some chassis of this model are equipped with a wave trap for the purpose of eliminating interference from code stations which operate on a frequency of approx: imately 455 kilocycles. This assembly consists of a coil and a trimmer condenser as illustrated by dotted lines in the Viring Diagram.
The wave trap should not be adjusted until all other adjustments have been made. To make the adjustment, feed a 455 kilocycle signal from the signal generator through &. 002 md. condenser into the antenna lead of the receiver. With the band selector switch turned to the Broadcast.Band position, the gang condenser set to approximately 60 in the dial, and the volume control full on, adjust the wave trap trimmer condenser for MINIMUM output.
Should the interfering station be operating on a frequency of slightly more or less than 455 kilocycles, the exact frequency should be determined with the aid of the signal generator. Then, instead of feeding a 455 kilocycle signal into the receiver the exact frequency of the interfering signal should be used. If it is not possible to determine the exact frequency of the interfering signal an antenna may be attached to the receiver and the receiver tuned to the position where the interfering signal is most noticeable. Then adjust the wave trap for minimum interference.

IMPORTANT ALIGNMENT NOTES When aligning the shortwave bands " OSC " trimmers care must be exercised to see that the circuits are aligned on the correct frequency which is approximately 910 kilocycles less as indicated on the dal. To check, increase generator output, tune in the generator frequency and then tune in the image frequency which should be weaker than the fundamental and come in approximately 910 kilocycles lower on the dial than the fundamental. If image cannot be tuned-in, the " OSC " trimmer is adjusted to the wrong peak. (Correct peak is the second peak on trimmer from the closed position). Repeat the original alignment procedure for more accurate adjustments. Always keep signal generator- output as low as possible to prevent action of the A.V.C. circuit.

WAVE TRAP Some chassis of this model are equipped with a wave trap for the purpose of eliminating interference from code stations which operate on a frequency of approximately 455 kilocycles. This assembly consists of a coil and a trimmer condenser as illustrated by dotted lines in the Wiring Diagram. The wave trap should not be adjusted until all other adjustments have been made. To make the adjustment, feed a 455 kilocycle signal from the signal generator through a. 0002 mfd. condenser into the antenna lead of the receiver. With the band selector switch turned to the Broadcast Band position, the gang condenser set to approximately 60 on the dial, and the volume control full on, adjust the wave trap trimmer condenser for MINIMUM output.. Should the interfering station be operating on a frequency of slightly more or less than 455 kilo cycles, the exact frequency should be determined with the aid of the signal generator. Then, instead of feeding a 455 kilocycle signal into the receiver the exact frequency of the interfering signal should be used. If it is not possible to determine the exact frequency of the interfering signal an. antenna may be attached to the receiver and the receiver tuned to the position where the interfering signal is most noticeable. Then adjust the wave trap for minimum interference.

VOLTAGE CHART
ALL VOLTAGES MEASURED FROM SOCKET PIN TO CHASSIS @ 117.3 VOLT LINE