TM 11-6625-3053-14
CHAPTER 6
GENERAL SUPPORT MAINTENANCE
SECTION I. REPAIR PARTS, SPECIAL TOOLS, TEST MEASUREMENT
AND DIAGNOSTIC EQUIPMENT (TMDE); AND SUPPORT EQUIPMENT
6-1. COMMON TOOLS & EQUIPMENT.
For authorized common tools and equipment refer to the Modified Table of Organization and Equipment (MTOE)
applicable to your unit.
6-2. SPECIAL TOOLS, TMDE & SUPPORT EQUIPMENT.
Refer to Section III of the Maintenance Allocation Chart (MAC) (Appendix B) for this information.
6-3. REPAIR PARTS.
Repair parts are listed and illustrated in the Repair Parts and Special Tools List (including Depot RPSTL) TM 11-6625-
3053-24P covering maintenance for this equipment.
SECTION II. TECHNICAL PRINCIPLES OF OPERATION
6-4. GENERAL.
This section describes the electrical functions of the AN/USM-213B signal generator. The discussion first describes the
overall function of the instrument and its major components. A detailed circuit description for each module follows.
6-5. ELECTRICAL FUNCTIONS (Figure 6-1).
The klystron oscillator (Item A and attenuator produces an RF signal between 800 and 2400 MHz. The frequency is
varied by the operator using the tuning knob. The output amplitude is also controlled by the operator using front panel
knobs. The power supplies (Item B provide the DC voltages which the klystron oscillator needs for its operation. The
leveling attenuator (Item C has two functions. When in the automatic leveling (ALC) mode, variations in output level
coming from the klystron oscillator are removed when the frequency is changed. This means that the operator does not
have to power set the attenuator when changing frequency. When in the non ALC mode, power levels are set manually.
The klystron oscillator output passes through the leveling attenuator unaltered. The other function of the leveling
attenuator is to modulate the RF output. Both functions of the leveling attenuator are controlled by the leveling and
modulation circuit (Item D. This circuit originates the square wave signal for INTERNAL SQUARE WAVE modulation,
and selectively feeds it or the externally received sine wave ampli- tude modulation (AM) & pulse modulation (PULSE)
signals when a modulated output is required.
6-1
