Microprocessor Board - HP 8114A Service Manual

HP 8 114A Service Guide

Microprocessor Board

The following checks can be performed on t,he Microprocessor Board:
Check Procedure
Visual Inspect t,he board carefully for dry joints, unsoldered
joints, or broken components
Clock
at the CLKOUT pin (66) on the Microprocessor. The
frequency should be 16.78 MHz (8.38 during reset).
If a clock signal is not found check crystal Yl
associated components. Also check C44, C49 and C66,
capacitors used in the VCO circuit
DIP Switches
Check that the switches on SW1 are set, according to the
following table:
Note that Section 1 in the DIP
Microprocessor clock line, and incorrect setting, or a
faulty switch section disables the Microprocessor
HP-IB If faults are suspected in connection with the HP-IB
Interface, check the ribbon cable that joins the HP-IB
socket to the Microprocessor Board. Using a resistance
meter,
check
cable conductors
Dividers Dividers U28A and U28B divide the system clock
to produce a clock for the HP-IB Interface. Use an
oscilloscope to check operation. Pin 3 on U28 is clock
input (16.78 MHz). Pin 5 gives the first divide-by-2
output (8.39 MHz) and pin 9 provides the final clock to
V CR2477. Its HP part number is 1420-0394. It is
capable of in excess of 5 years' operation. Using a
high impedance voltmeter measure across the battery
terminals. If you suspect that the battery is faulty,
change it, by unsoldering it from the PC Board.
check that there is a clock signal
Switch
for continuity along each of the ribbon
and its
disconnects the