HP 8114A - Microprocessor Board

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
IJsing an Oscilloscope, check that there is a clock signal
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 and its
associated components. Also check C44, C49 and C66,
capacitors used in the VCO circuit
DIP Switches
HP-IB
Dividers
Rattery
Check that the switches on SW1 are set, according to the
following table:
Table 5-4. Settings for DIP Switch Sl
Note that Section 1 in the DIP Switch disconnects the
Microprocessor clock line, and incorrect setting, or a
faulty switch section disables the Microprocessor
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 for continuity along each of the ribbon
cable conductors
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
UlO, the HP-IB IC, just over 4 MHz.
BTl is a 3 V Lithium battery, type: Panasonic +3
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.
5-l 0 Troubleshooting