Static Handling; Recommended Test Equipment; Theory Of Operation; Introduction - HP 3457A Service Manual

Service
8-8. STATIC HANDLING
8-9. Static electricity is a familiar phenomenon which, except for an occasional shock, doesn't seem very
serious. It has been proven in the electronics industry, however, that electrostatic discharge (ESD) is a major
cause of component failure. In many cases, the component damaged may not fail immediately but cause
poor instrument reliability and additional repairs at a later date. ESD damage can occur at static levels too
low for human perception. It has been shown that ESD can affect both active and passive devices.
8-10. Any assembly removed from the instrument MUST be handled in accordance with anti-static handling
procedures. This includes the optional plug-in assemblies.
8-1 1. The following guidelines are the minimum requirements for a static-safe service environment:
The work bench must be equipped with a conductive table mat. The mat should be connected t o
earth ground through a 1 megohm resistor. The mat must be equipped with at least one connection
for connecting wrist straps.
All persons who handle and service the instrument must wear a conductive wrist strap in contact
with bare skin. This wrist strap must be connected t o the conductive table mat.
All metal equipment at the work station must be grounded t o earth ground. This includes soldering
irons, de-soldering tools, shelving, and equipment stands.
Only one common ground can be provided at a work station.
The work station must be kept free of non-conductive items such as, common plastics, polybags,
cardboard, cigarette or candy wrappers. There must be no rugs or carpet on the floor, shelving, or
bench top.
Proper containers must be used for shipping, storing and transporting assemblies.
8-12. RECOMMENDED TEST EQUIPMENT
8-13. Equipment t o test and repair the H P 345714 is listed in Section I (Table 1-3) of this manual.
8-14. THEORY OF OPERATION
8-1 5. Introduction
8-16. The following paragraphs provide a simplified explanation of the HP 3457A circuit operation. Refer
t o the simplified block diagram in Figure 8-1 for the following description.
8-17. The HP 3457A can be divided into two basic sections; the Chassis Common circuitry and the Floating
(isolated) Common circuitry. The chassis common circuitry provides instrument control and communication
with other instruments, through the HP-IB, or the user through the front panel keyboard and display. The
floating common circuitry is responsible f o r converting the analog input signals t o digital information. The
two sections communicate with each other through the isolation logic circuitry.
8-18.
Chassis Common Section
8-19. The Chassis Common section consists of digital circuits and associated power supplies. The main cir-
cuits are the Master Processor, HP-IB Interface, Front Panel Interface (keyboard and display) and the
Chassis Common Isolation Logic.