HP 5004A, Operating And Service Manual

Page: 62 / 74

Model
Service
8-60. Display Scan and Comparator Strobe
8-61. The clock signal is used to time both the display scan and signature compartor strobe
circuits. The digit display lamps are enabled less than full-time to conserve power.
NOTE
The switch i s separate but related to the front
panel SELF-TEST switch.
8-62. Service (Troubleshooting) Mode
8-63. On the main assembly of the a two-position switch, labeled
can be used during fault locating (troubleshooting) procedures if the is not operating
correctly.
8-64. Power Supply
8-65. Alternating current line supply (mains) voltage is converted to the two positive and
negative regulated direct current voltages required in the
by the power supply circuit.
8-66.
THEORY (PRINCIPLES OF OPERATION)
8-67. following paragraphs give the circuit theory (principles of operation) for the
Signature Analyzer to explain the schematic diagram. A previous section describes the at
the block diagram level. This BLOCK DIAGRAM DESCRIPTION should be studied and learned
before the following paragraphs are studied.
8-68. Purpose of
8-69. The Signature Analyzer
is
designed to be used in testing the correctness of oper-
ation of certain complex digital logic electronic instruments or systems. A technique of testing
called signature analysis is used with the
and compatible instruments. Refer to the para-
graph titled Signature Analysis in Section I for an explanation of signature analysis.
8-70. Schematic Diagram
8-71. The schematic diagram i s presented with the four inputs on the left side, and the
flow of signals i s generally from the left to the right side where the output indicators are pre-
sented. Outputs are four digits (seven-segment
and two single-LED
indicators. Refer to the schematic diagram notes for an explanation of the schematic symbol
system used. The ac line power input and dual-voltage (regulated) power supply are on the lower
left side of the schematic.
8-72. Gating Signals Pod
8-73. gating signals pod is the input for the CLOCK, START, and STOP signals to the
Requirements for these signals are in Section I. A voltage regulator, U4, for
on the pod board reduces power dissipation in the main assembly. Amplifier, is used as a
voltage follower to provide the 1.4-volt reference level for the three input amplifier-converters.
All three input signals are each applied to three separate identical circuits. The input
converters produce high-speed complementary-output ECL-level signals for the main assembly.
8-74. Edge Selection
8-75. The three ECL-level pulse signals from the pod (START, STOP, and CLOCK) are applied
separately to three front-panel switches which may be used to select the polarity of any input
signal. Changing the polarity of a signal effectively selects the opposite edge of the input signal
as the control for that channel.