FIG. 1. WIRING DIAGRAM OF MODEL F - 548

MODEL F - 546

June, 1936

SPECIFICATIONS
The Amrad Model F - 546 is a five-tube superheterodyne receiver designed for operation from a six-volt storage battery. It contains a completely shielded, built-in
GREEN 540-1730 Kilocycles
RED 2.3- 7.0 Megacycles

TUBES AND VOLTAGE LIMITS The following table gives the functions of the tubes used, together with the voltage readings between the tube socket contacts and the chassis. Voltage readings should be taken with a 1000 ohm per volt, 250 volt power supply unit which employs a self-rectifying type vibrator.
The tuning range of the receiver is from 540 to 7000 kilocycles and is divided into two bands as follows: (American Broadcast Band) (High Frequency Band) voltmeter (except filaments with the volume control full on and no signal input. The filament voltages should be measured with an accurate low range DC voltmeter (approximately 0 to 10 volts). Voltage limits may vary plus or minus 10 % of values given.

ALIGNMENT PROCEDURE

All the circuits, in this receiver are very accurately adjusted at the factory and normally should need no further adjustment. However, if it is definitely known that an adjustment is necessary the circuits can best be properly aligned with the use of a modulated signal generator and an output motor.

CONNECTING OUTPUT METER
Connect one terminal of the output ineter to the plate and the other terminal to the screen of the 38 Output tube. Be sure the meter is protected from D.C. by connecting a condenser (.1 mfd. or larger-pot electrolytic) in series with one of the leads.

1. Tuning I - F Amplifier to 450 Kilocycles.
(a) Connect the output signal generator through a 02 mfd. condenser to the top cap of the 6A7 tube, leaving the tube's grid clip in place. Connect the ground lead from the signal generator to the " GND " terminal of the receiver, KEEP THE GENERATOR OUTPUT LEAD AS FAR AS POSSIBLE FROM THE GRI LEADS OF THE OTHER SCREEN GRID TUBES.
(b) Set the station selector so that the tuning con denser plates are completely out of mesh. Turn the vol. ume control knob to the right (ON) and turn the tone control knob to the left (TREBLE).
(c) Turn the band selector switch to the right (High Frequency Band).
(d) Set the signal generator to 450 kilocycles.
(e) Adjust both trimmers located on top of the 2nd I - F transformer for maximum output.
(f) Adjust both trimmers located on top of the 1st 1 - F transformer for maximum output.
ALWAYS USE THE LOWEST SIGNAL GENERATOR OUTPUT THAT WILL GIVE A REASONABLE OUTPUT METER READING.

2. Aligning R - F Amplifier.
When aligning the R - F amplifier the output lead from the signal generator is connected to the antenna (" A - 1 ") terminal of the receiver " through a.00025 mfd. cota denser.
Each band should first be shunt aligned and then series aligned. The band selector switch should be set for the band being aligned and the signal generator should be set to the frequency indicated for each adjustment.
Adjust the " OSC " R - F " and " ANT " shunt trimmers in the order given for maximum output. Tune the station selector to the signal generator for maximum out: put and then check the adjustments of the " R - F " and
ANT " trimmers in the order given. Do not readjust the " OSC " trimmer. NOTE: When aligning the High Frequency Band care must be exercised so that the circuits will be aligned on the fundamental frequency rather than on the image frequency which is approximately 900 kilocycles less than the fundamental. To check on this, increase the output of the signal generator approximately ten times and try to tune in the signal at both the gen. erator frequency as indicated on the station seloctor dial and at approximately 900 kilocycles below the correct frequency. If the circuits have been properly aligned the signal can be tuned-in at both positions but much stronger at the correct position.
To adjust the series " trimmers set the signal gener ator to the frequency indicated and then tune-in this signal with the station selector for maximum output, Adjust the " series " trimmer while rocking the tuning condenser back and forth slightly, until no further im provement in output can be obtained,