Micro P Rocessor Board - HP 8110A Service Manual

M
icro
p
rocessor
B
oar
d
The
f ollowing checks can be
p
erformed on the Microprocessor Board :
Check Procedure
HP 811 OA Service Guide
Visual Inspect the
b oard carefully for dry
j
oints, unsoldered
j
oints, or
b roken components
Clock
Using an Oscilloscope, check that there i s α
c
lock signal
at the CLKOUT pin (66) on the Microprocessor . The
f requency should be 16 .78 MHz (8 .38 during reset) . If
α
c
lock signal i s not
f ound check crystal Υ 1
a
nd its
associated components. Also check C44, C49 and C66,
capacitors used in the VCO circuit
DIP
S
witches
Check t hat the switches on SW1 are set, according to
the
f
ollowing table:
Table 4-2. Setti n
gs for DI
P
Switc
h
S1
Switch Settings
Pos: 1 2 3 4 5 6 7 8
131Ν : 1 1 1 1 0 1 1 0
N
ote that Section 1 in the DIP
S
witch disconnects the
Microprocessor clock line, and incorrect setting, or α
f aulty switch section disables the Microprocessor
HP- ΙΒ
If faults are suspected in connection with the HP- ΙΒ
Interface, check the ribbon cable that
j
oins the HP-ΙΒ
socket to the Microprocessor B oard.
U
sing α resistance
m eter, check for continuity along each
o
f the ribbon
cable conductors
Dividers Dividers
U
28A and
U
28B divide the system
c
lock
to
p
roduce α
c
lock for the HP-ΙΒ Interface .
U
se an
oscilloscope to check
o
peration . Pin 3 on
U
28 is clock
input (16.78 MHz) . Pin 5 gives the first divide-by-2
output (8.39 MHz) and pin 9
p rovides the final clock to
U
10, the HP- ΙΒ IC,
j
ust over 4 MHz .
B
attery ΒΤ 1 is α 3 V
Lit
h
ium battery, type: Panasonic +3
V C R2477.
I
ts HP part number is 1420-0394 .
I
t is
capable of in excess of 5
y
ears' operation.
U
sing α
high impedance voltmeter
m
easure across the
b
attery
terminals . If you s uspect that the
b
attery is
f
aulty,
change it by unsoldering it
f
rom the P C Board.
Trou
b
les
h
ooting 4- 1 5