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TEST
EQUIPMENT
Test
Equipment
listed
by Manufacturer
illustrates typical
or equivalent
equipment used
by
SAMS'
Engineers
to
obtain
measurements
and
is
compatible
with
most
types
used
by
field
service technicians.
TEST
EQUIPMENT (COMPUTERFACTS
)
Equipment
Name
B
&
K
Precision
Equipment
No,
Sencore
Equipment
No.
Simpson
Equipment
No.
OSCILLOSCOPE
1570A,1590A,1596
SC61
454
LOGIC
PROBE
DP51
LOGIC
PULSER
DP101
DIGITAL
VOM
2830
DVM37,DVM56,SC61
463,467,470,474,467E
ANALOG VOM
277
260-7,160,165,
260-6XL.260-7P,
260-6XLP
ISOLATION
TRANSFORMER
TR110,1604,1653,1655
PR57
FREQUENCY COUNTER
1803,1805
FC71.SC61
710
COLOR
BAR
GENERATOR
1211A,1248,1251,1260
CG25.VA62
431
RGB GENERATOR
1260
FUNCTION
GENERATOR
3020
420A.420D
HI-VOLTAGE
PROBE
VOM/DMM
Accessory probes
HV-44
HP200
248
00168,00411,00749
TEMPERATURE PROBE
TP-28
IR-10,00760,00758;
383,389,388
CRT ANALYZER
467,470
CR70
COMPUTER
DEAD
TROUBLESHOOTING
Disconnect
all
peripheral
equipment from
Computer
except
the Monitor.
Turn
Computer
On
and check
for
proper opera-
tion.
If
Computer
operates
properly, turn
Computer
Off
and
reconnect
peripherals
one
at
a
time.
Recheck
the operation
of
Computer
each
time a
peripheral
is
connected
until
the
peripheral
causing
the
problem
is
found.
If
Computer
does
not
operate
properly with peripherals
disconnected,
check
for
5.0V
at
pin 3
of
SALT
IC
(IC1).
If
the
voltage
is
missing,
refer to
the
"Power
Supply"
section
of
this
Troubleshooting
guide.
If
the
power
supply
voltage
is
correct,
check
for
pulses
on Data
lines (pins
24
thru 31)
and
Address
lines
(pins
8 thru
23) of
CPU
IC
(IC9).
If
pulses
are
missing
at
any
of
the
pins, refer to
the
"Microprocessor
Operation"
section
of this
Troubleshooting
guide.
If
pulses
are
present
at
all
of
the
pins, refer to
the
"Video"
section.
POWER
SUPPLY
Computer
is
dead.
Check
for
5.0V
at pin
3
of
SALT
IC
(IC1).
If
the voltage
at
pin 3 of IC1
is
less
than
4.75V,
measure
voltage
at
collector
of
Voltage Regulator
Transistor
(Q1).
If
Q1
collector
voltage
is
at least
7.5V,
measure
the voltage
drop across
Resistor
R2.
If
the voltage
across
R2
is
0.2V
or
greater,
the
power
supply
may
be
in
the foldback
(shut-
down) mode. Check
Capacitors
C5,
C6
and C1
1
for
possible
shorts.
Also
check
for
other shorted
components
that
may
be
overloading the
power
supply.
If
the voltage
across
R2
is
approximately
1.0V,
check
Resistor
R2
for
an open
condi-
tion.
If
the voltage
across
R2
is
less
than
0.2V,
check
Tran-
sistor
Q1 and
IC1.
If
voltage
at
the collector
of
Q1
is
less
than
7.5V,
check
for
approximately
17.5VAC between
the
anodes
of
D3
and
D4.
If
the voltage
is
missing,
check
Power
Switch
(SW1).
Also
check Power Transformer
(T1)
for
a possible
open
winding.
If
the
17.5VAC
is
present,
check Diodes D3 and
D4.
Also
check
Capacitors
C2
and
C3
and
the printed
circuit
board
for
possible
shorts.
If
5.0V
is
present
at
pin 3 of
IC1,
check
for
approximately
-
10V
at
pin
15
of IC1.
If
-
10V
is
missing,
check Diodes
D1
and D2 and
Capacitor
C1.
If
the voltages are
normal
at
pins
3
and
15
of IC1,
use
a
scope
to
check
for
AC
ripple at pin
3
of
IC1.
The
AC
ripple
should be
less
than 0.4V
peak-to-peak.
If
excessive
60Hz
ripple
is
present,
check Diodes
D3
and
D4.
If
excessive
120Hz
ripple
is
present,
check
Capacitor
C2.
If
excessive 150-200Hz
ripple
is
present,
check
Capacitors
C5
and C11 and
IC1.
MICROPROCESSOR
OPERATION
Computer
is
dead,
power
supply
checks
good.
Use
a
scope
to
check
the
data
lines (pins
24
thru 31 of IC9)
for activity.
If
there
is
no
activity
on
the data
lines,
check
the operation
of
the reset
circuit
by observing
the
logic
reading
at
pin
37
of
the
CPU
IC
(IC9).
Pin
37
of
the
CPU
should
beLow when
the
Computer
is
turned
On
and
then immediately
go
High.
The
reading
on
pin
37 should
also
be
Low
whenever
the
Reset
Switch (SW2)
is
pressed.
If
the
logic
reading
is
not correct
at
pin
37
of
the
CPU
when
the
Computer
is
turned On,
check
Capacitor C48,
Diodes
D10,
D11
and D12 and
Resistor R20.
If
the
Power
On
reset
works
properly but the
Reset Switch
(SW2) does
not work,
check Switch
SW2,
Capacitor C58,
Resistor
R22 and Diodes
D11 and
D12.
If
the
reset
circuit
is
working
properly,
check
for
the
894.886KHZ
E
and
Q
clock pulses
at
pins 34
and
35
of
CPU
IC9.
If
the clock pulses are missing,
check
the
waveform
at
pin
6
of
the
SAM
(Synchronous Address
Multiplexer) IC22.
If
the
waveform
is
missing
at
pin %,
check
Crystal X1,
Capacitors
C43
and
C44, Resistor
R15 and Trimmer
TC1.
If
the
waveform
is
present
at
pin
6
of IC22,
check
for
the
Q
and
E
clock pulses
at
pins 13
and
14
of IC22.
If
the clock
pulses
are
present
at
pins 13
and
14
of IC22,
check
IC22
and
Capacitors
C37 and
C38.
8
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