Troubleshooting; Introduction; General Block Diagram Theory Of Operation - HP 3455A Operating And Service Manual

Model 3455A
Section VIII
TROUBLESHOOTING
8-174, INTRODUCTION.
8-175, The following portions of this manual contain.
information to aid in troubleshooting and repair of the
4455A. This information consists of a General Block
Diagram Theory of Operation, a Preliminary Trouble-
shooting Check, and eight Service Groups. An instru-
ment block diagram and schematics are also included in
this section of the manual.
8-176. General Block Diagram Theory of Operation.
8-178. To understand the basic operation of the 3455A,
the instrument can be divided into two sections. These
sections of the Outguard Section and the Inguard Sec-
tion.
B-179. Outguard Section.
8-180. The Outguard Section consists of most logic cir-
cuits and their power supplies. These circuits function as
the internal main controller, HP-IB interfacing, and
front panel interface of the instrument.
sass-o-aa3s
8-181. The main controller circuits are used to control
communication between the front panel. HP-IB inter-
face, and the Inguard Section. The controller also per-
forms mathematical calculations to correct measure-
ment data, and to provide instrument scaling or percent
error readings.
8-182. The heart of the main controller circuits is a pro-
cessor (referred to as the nanoprocessor) used in con-
junction with the main controller ROMs. The processor
and ROMs are located on the A3 board. The ALUs are
used for calculations and are located on the Al mother-:
board.
8-183. The front panel is used for the manual operation
of the instrument and to display readings. By pressing a
pushbutton on the front panel, the controller receives a
message to do the operation requested by the operator
(DC, AC, etc.). The main controller then sends a
message to the inguard controller to do the operation.
After the operation is completed, the inguard controller
then sends information back to the main controller. The
information is then converted and displayed on the
front panel.
8-184. The HP-IB circuits are used to communicate bet-,
ween the HP-IB and the instruments main controller.
Information can pass either from the HP-IB to the main
Figure 8-44. Simplified Block Diagram.
8-35