MAINTENANCE & ALIGNMENT

The FRG-7 has been carefully aligned and tested at the factory using the precise test instruments before shipment and, with normal usage, it should not require other than the usual attention given to any electronic equipment. Service or replacement of major component may require substantial re alignment, however, under no circumstances, should realignment be attempted unless the operation of the receiver is fully understood and the malfunc tion has been fully analyzed and traced to misalign ment. Service work should only be performed by experienced personnel using proper test equipment.

TEST EQUIPMENT REQUIRED

(1) RF Signal Generator; Hewlett-Packard Model 606A or equivalent with one volt output at an impedance of 50 ohms and a frequency coverage to 30 MHz.

(2) Vacuum Tube Volt-Ohm Meter (VTVM): Hewlett-Packard Model 401B or equivalent VTVM with RE probe workable to 60 MHz.

(3) Sweep Generator and Oscilloscope workable to 60 MHz.

(4) Frequency Counter: Yaesu YC-355D or equivalent workable to 60 MHz.

RF UNIT PB-1526

(1) 55 MHz Passband Circuit, T₁₀₅ ~ T₁₀₈

Set the BAND switch to D and the MHz dial to 20 MHz position. Disconnect the antenna. Connect the sweep generator output between TP₁₀₃ and TP₁₀₂ (ground), and the oscilloscope input between TP₁₀₄ and TP₁₀₅ (ground). Set the center fre quency of the sweep generator to 55 MHz and align T₁₀₅ through T₁₀₈ until the scope indicates the curve shown in Fig. 5. Disconnect the sweep generator and the scope.

Fig. 5

(2) Balanced Mixer, VR₁₀₁, TC₁₀₆

Set the BAND switch to A and the MHz dial to 0. Disconnect the antenna, and connect its output to antenna terminal. Tune the receiver to the internal spurious signal at 910 kHz. Adjust VR₁₀₁ and TC₁₀₅ for minimum S-meter indication.

(3) Antenna Coil and Trimmer, T₁₀₁ ~ T₁₀₄

Connect the signal generator output to the antenna terminal SW₂ and connect SW₁ and BC terminals with a copper wire.

Set the signal generator to 0.5 MHz, the BAND to A and PRESELECT to 0.5. Tune the receiver to the signal generator signal. Adjust T₁₀₁ for maximum S-meter reading. Repeat this procedure at the frequencies shown in Table 4.