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RACAL RA6790/GM ALIGNMENT AND TUNING MANUAL From [email protected] February 2003 Racal RA6790/GM Alignment & Tuning Manual CHAPTER 3 ASSEMBLED RECEIVER ALIGNMENT AND TEST 3-1. INTRODUCTION. This chapter provides both alignment procedures and an end -to-end check for an assembled Receiver. The information is presented in two sections with alignment procedures contained in Section I and procedures for an end-to-end check presented in Section II. The alignment procedures are designed to permit alignment of any one or all of the various functions in the Receiver; however, the adjustments in some functions interact with other functions so chat care must be taken when any one function alone is aligned. The end-to-end checks are designed to make sure that a Receiver is operational after assembly of new or repaired circuit cards or modules. SECTION I. ASSEMBLED RECEIVER ALIGNMENT 3-2. GENERAL. The circuit card and module assemblies may be aligned and checked after they are installed in a working Receiver. The following paragraphs provide detailed step-by- step instructions for aligning the Receiver assemblies. The alignment procedures require that external power be connected to the Receiver, the Receiver power switch turned on and that the mode, bandwidth, AGC and frequency be set as described in each procedure. Refer to T.O. 31R2 -2URR-251 for location of circuit cards and adjustments. a. Power Supply Assembly AlO. The power supply used in the Receiver does not contain any adjustments or controls other than the line voltage select card located in A10J1. If all voltages checked correctly as specified in Section XI of Chapter 2, it can be assumed that the power supply is functioning properly. If the power supply has not been tested then the 3-1 voltage levels as spelled out in Chapter 2 should be checked before performing any alignment procedures. WARNING The filter capacitors used in the power supply will retain an electrical charge after power is removed. The capacitors should be discharged slowly by shorting the terminals through a protected resistive device. Disconnect the ac line cord from A10J1. Remove the metal cover from the power supply and then reinsert line cord and turn Receiver power on. Using the digital multimeter, check the voltages appearing on connector Page 2 of 20 Racal RA6790/GM Alignment & Tuning Manual A10A1 (refer to Table 2-28 in Chapter 2). Do not disconnect power output connector J3 during these measurements, as this will unload the power supply and could result in erroneous readings. b. Low Pass Filter, Assembly Al. Test equipment required to align the low pass filter Al is the Spectrum Analyzer listed in Table 1-2. (1) Connect the output of the Tracking Generator to the RF IN connector Jl of