Keithley 7038, Инструкция по эксплуатации

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Servicing
4-7
4.3.6 Special handling of static-sensitive devices
CMOS and other high-impedance devices are subject to pos-
sible static discharge damage because of the high-impedance
levels involved. When handling such devices, observe the
precautions listed below.
NOTE
To prevent damage, assume that all parts
are static-sensitive.
• Such devices should be transported and
handled only in containers specially de-
signed to prevent or dissipate static
build-up. Typically, these devices will
be received in anti-static containers
made of plastic or foam.
• Keep these parts in their original con-
tainers until ready for installation or
use.
• Remove the devices from their protec-
tive containers only at a properly
grounded workstation. Also, ground
yourself with an appropriate wrist strap
while working with these devices.
• Handle the devices only by the body; do
not touch the pins or terminals.
• Any printed circuit board into which the
device is to be inserted must first be
grounded to the bench or table.
• Use only anti-static type de-soldering
tools and grounded-tip soldering irons.
4.4 Principles of operation
The following paragraphs discuss the basic Model 7038 op-
erating principles that can be used as an aid in troubleshoot-
ing the card. The schematic diagram of the card is located at
the end of Section 5.
4.4.1 Block diagram
Figure 4-5 shows a simplified block diagram of the Model
7038. Key sections include the relay data control and driver
ICs, the relays, and the card configuration memory. These
various elements are discussed in the following paragraphs.
4.4.2 Relay control
Card relays are controlled by serial data transmitted from the
host switching mainframe via the DATA line. Each control
byte is shifted in serial fashion into latches located in the card
relay driver IC (U101, U102, U103). The serial data is
clocked in by the CLK (clock) line.
To
Mainframe
Memory
U100
From
Mainframe
+6V
Data
Clock
Strobe
Relay
Driver
U101,102,
103
Power Up/Down
Safeguard
Out A
MUX
A
K106,107,
108
1
2
3
4
Multiplexer A
Inputs
Out B
MUX
B
K103,104,
105
5
6
7
8
Multiplexer B
Inputs
Out C
MUX
C
K100, 101,
102
9
10
11
12
Multiplexer C
Inputs
Figure 4-5
Block diagram