TM 9-6625-1753-14
C3
CHAPTER 1
INTRODUCTION
Section I. GENERAL
1-1. Scope
a. This manual contains instructions for operation, and for organizational, DS, and GS maintenance of oscilloscopes
765MH and 765MH/F (Portascopes) (Fig. 1-1).
b. Precautionary measures to be taken during operation and maintenance of the oscilloscopes are contained in
appropriate paragraphs of this manual.
1-2. Reporting Equipment Publication Improvements
Report of errors, omissions, and recommendations for improving this publication by the individual user is encouraged.
Reports should be submitted on DA Form 2028 (Recommended Changes to Publications) and forwarded direct to
Commander, U.S. Army Missile Command, ATTN: AMSMI-NPM, Redstone Arsenal, AL 35809.
1-3. Maintenance Allocation
The prescribed maintenance responsibilities will apply as reflected in TM 9-6625-1753-25P.
1-4. Forms, Records and Reports
Refer to TM 38-750 for the forms, records, and reports required from units maintaining this equipment.
1-5. Differences Among Models
a. General. A difference among models exists when two or more configurations of the same item are used in the
equipment. In this equipment these differences are permanent. A permanent difference among models exists when an
item is changed during manufacture, but the change does not warrant modification (or retrofit) of the item already in the
field. This difference usually arises when the equipment is improved, although the older model can perform its function
satisfactorily.
b. Oscilloscope 765MH Main Frame Changes. There are two models of the main frame. The earlier model has an a
11-vacuum tube high-voltage rectifier circuit, while the later model has a solid-state high-voltage rectifier circuit.
Replacing the vacuum tube rectifier with solid state rectifiers increases the reliability of the high-voltage power supply.
c. Oscilloscope 765MH/F. With the exception of circuits which provide a higher frequency response, oscilloscope
765MH/F is similar to the newer models of oscilloscope 765MH. To obtain the higher frequency response, CRT
termination network 7062 is incorporated into the main frame. This termination provides facilities for adapting dual trace
plug-in 79-02A to the unit. Dual trace plug-in 79-02A has a frequency response of 100 mc to the 3 db point, and
frequencies as high as 250 mc can be observed using the instrument with this plug-in.
d. Oscilloscope 765MH/F. The round CRT of previous models has been replaced with a rectangular CRT. The high
voltage power supply has been replaced with a circuit board assembly. A Z-axis circuit board assembly has been added
to allow low level DC inputs to Z-axis.
Note. Do not use shorting type cap plug on EXT Z-axis input connector.
1-6. Nomenclature and Reference Designations
a. Table 1-1 lists the reference designation and official nomenclature of the assemblies that comprise oscilloscopes
765MH or 765MH/F (Portascope).
1-1
