Motorola SABER NTN4734A Manuale di istruzioni - Pagina 7

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Motorola SABER NTN4734A Manuale di istruzioni
c. Reset Circuit
Integrated circuit U5 is
a
"watchdog"
timer.
At least
once every second, a positive signal
from U3, pin
31,
is
received
at U5, pin 2.
This
signal keeps
Q18 from
reset-
ting the microcomputer.
If
a
problem
occurs
in
the micro-
computer,
such
as
the microcomputer's internal timer
ceasing
to
function correctly, the microcomputer
stops
sending the signal
at
U3,
pin
31.
As
a
result, the following
sequence occurs: U5,
pin
3,
goes
low, turning off Q19.
This
turns on Q18, which
resets the
microcomputer.
When
the microcomputer is reset, Q14 is turned on, pulling U5,
pin
2, low, and resetting the U5
timer.
Resetting
the timer
causes
U5,
pin
3, to
go high, which
turns on Q19, turns
off Q18,
and pulls the microcomputer out of reset via U3,
pin 2.
d. Interrupt
Circuit
Transistor Q4 is normally turned
on. But,
if
the battery
is removed, or
if
"contact bounce" occurs, the voltage at
the collector
of
Q1
goes
high, which turns off
Q4
and pulls
U3,
pin 3, low.
This
low
signal
interrupts
U3's
internal pro-
cessor
and
keys
the microcomputer
to
check
the battery's
RC
and RT.
If
the interrupt
was
just contact bounce, then
the microprocessor
will
continue
its
normal function.
If
the
interrupt
was a
removed
battery, the microcomputer
blanks
the display.
If
the battery
is
open, the microcompu-
ter
senses
a probiem and, via U3,
pin
36, keys the orange
LED
to
flash
on and off.
7.
MAINTENANCE
a.
Fuse
If
the charger
does
not
operate,
check fuses
and
F2,
and replace
if
necessary.
If
the replaced fuse "blows,"
check
for short
circuits
in
the transformer,
charger circuits,
and transistor
Q1.
b.
Contacts
If
the red
Charging LED
does
not turn on with
a
radio
or battery inserted into the
pocket,
check
the contacts of
the battery or
charger
for
dirt,
grease,
or other foreign
ma-
terials.
Clean
the contacts,
if
necessary,
with
a soft cloth.
CAUTION
THE
FOLLOWING MAINTENANCE
PROCEDURES
SHOULD ONLY BE
PERFORMED BY
QUALIFIED
SERVICE
PERSONNEL:
c. Voltage Measurements
The
de
voltage measurements table below
lists the vol-
tage levels
that should be present with varying batteries
and operating conditions.
DC VOLTAGE
MEASUREMENTS
BATTERY
BATTERY
at
Q7
Q15
U2
U3
CHARGING
CURRENT
TYPE
CONDITION
IN
2
|
21
224
23]
24°
297
40
(mA)
B+
NO
BATTERY
17.0
17.0
8.1
0.2
0
17.0 17.0
0
48
2.8
49
49
0
49
RAPID
NTN4537A, NTN4592A
15.5
148
102
0.7
0.1
15.5 15.5
32
32
19
48
1.94
3.5
0.5
27
3.4
49
CHARGE
CHARGE
NTN4597A, NTN4592A,
16.7
16.2
9.1
1.0
0.4
16.7 16.7
03
03
0.1
48
0.14
3.1
0.2
2.5
0
49
COMPLETE
NTN4538A, NTN4593A,
RAPID
14.7
14.0
10.7
0.8
0.2
147
14.7
64
64
3.5
48
3.55
37
1.0
28
3.4
49
1080
NTN4657A, NTN4671A
CHARGE
NTN4538A, NTN4593A,
CHARGE
16.7
16.1
8.7
1.0
0.4
16.7 16.7
05
05
0.3
48
0.29
3.0
28
2.6
0
49
NTN4657A, NTN4671A
COMPLETE
NTN4539A, NTN4594A
RAPID
14.0
13.4
105
0.8
0.2
111
10.3
90
90
5.0
48
4,93
3.6
1.6
2.9
34
49
1500
CHARGE
NTN4S39A,NTN4594A
CHARGE
COMPLETE
16.6
16.0
8.9
1.0
0.4
16.6
16.6
07
07
0.4
48
0.36
29
0.9
2.6
0
49
125
0
0
0
60
50
90
NOTES:
1.
ALL VOLTAGES REFERENCED TO CHARGER
GROUND.
2,
VOLTAGES AT
PIN
DESIGNATED
*
WLL VARY
WITH
THE VOLTAGE OF THE
BATTERY.
3,
VOLTAGES AT
PIN
DESIGNATED
**
WILL
VARY
WITH
THE TEMPERATURE OF
THE BATTERY.
4
c. Reset Circuit
Integrated circuit U5 is
a
"watchdog"
timer.
At least
once every second, a positive signal
from U3, pin
31,
is
received
at U5, pin 2.
This
signal keeps
Q18 from
reset-
ting the microcomputer.
If
a
problem
occurs
in
the micro-
computer,
such
as
the microcomputer's internal timer
ceasing
to
function correctly, the microcomputer
stops
sending the signal
at
U3,
pin
31.
As
a
result, the following
sequence occurs: U5,
pin
3,
goes
low, turning off Q19.
This
turns on Q18, which
resets the
microcomputer.
When
the microcomputer is reset, Q14 is turned on, pulling U5,
pin
2, low, and resetting the U5
timer.
Resetting
the timer
causes
U5,
pin
3, to
go high, which
turns on Q19, turns
off Q18,
and pulls the microcomputer out of reset via U3,
pin 2.
d. Interrupt
Circuit
Transistor Q4 is normally turned
on. But,
if
the battery
is removed, or
if
"contact bounce" occurs, the voltage at
the collector
of
Q1
goes
high, which turns off
Q4
and pulls
U3,
pin 3, low.
This
low
signal
interrupts
U3's
internal pro-
cessor
and
keys
the microcomputer
to
check
the battery's
RC
and RT.
If
the interrupt
was
just contact bounce, then
the microprocessor
will
continue
its
normal function.
If
the
interrupt
was a
removed
battery, the microcomputer
blanks
the display.
If
the battery
is
open, the microcompu-
ter
senses
a probiem and, via U3,
pin
36, keys the orange
LED
to
flash
on and off.
7.
MAINTENANCE
a.
Fuse
If
the charger
does
not
operate,
check fuses
and
F2,
and replace
if
necessary.
If
the replaced fuse "blows,"
check
for short
circuits
in
the transformer,
charger circuits,
and transistor
Q1.
b.
Contacts
If
the red
Charging LED
does
not turn on with
a
radio
or battery inserted into the
pocket,
check
the contacts of
the battery or
charger
for
dirt,
grease,
or other foreign
ma-
terials.
Clean
the contacts,
if
necessary,
with
a soft cloth.
CAUTION
THE
FOLLOWING MAINTENANCE
PROCEDURES
SHOULD ONLY BE
PERFORMED BY
QUALIFIED
SERVICE
PERSONNEL:
c. Voltage Measurements
The
de
voltage measurements table below
lists the vol-
tage levels
that should be present with varying batteries
and operating conditions.
DC VOLTAGE
MEASUREMENTS
BATTERY
BATTERY
at
Q7
Q15
U2
U3
CHARGING
CURRENT
TYPE
CONDITION
IN
2
|
21
224
23]
24°
297
40
(mA)
B+
NO
BATTERY
17.0
17.0
8.1
0.2
0
17.0 17.0
0
48
2.8
49
49
0
49
RAPID
NTN4537A, NTN4592A
15.5
148
102
0.7
0.1
15.5 15.5
32
32
19
48
1.94
3.5
0.5
27
3.4
49
CHARGE
CHARGE
NTN4597A, NTN4592A,
16.7
16.2
9.1
1.0
0.4
16.7 16.7
03
03
0.1
48
0.14
3.1
0.2
2.5
0
49
COMPLETE
NTN4538A, NTN4593A,
RAPID
14.7
14.0
10.7
0.8
0.2
147
14.7
64
64
3.5
48
3.55
37
1.0
28
3.4
49
1080
NTN4657A, NTN4671A
CHARGE
NTN4538A, NTN4593A,
CHARGE
16.7
16.1
8.7
1.0
0.4
16.7 16.7
05
05
0.3
48
0.29
3.0
28
2.6
0
49
NTN4657A, NTN4671A
COMPLETE
NTN4539A, NTN4594A
RAPID
14.0
13.4
105
0.8
0.2
111
10.3
90
90
5.0
48
4,93
3.6
1.6
2.9
34
49
1500
CHARGE
NTN4S39A,NTN4594A
CHARGE
COMPLETE
16.6
16.0
8.9
1.0
0.4
16.6
16.6
07
07
0.4
48
0.36
29
0.9
2.6
0
49
125
0
0
0
60
50
90
NOTES:
1.
ALL VOLTAGES REFERENCED TO CHARGER
GROUND.
2,
VOLTAGES AT
PIN
DESIGNATED
*
WLL VARY
WITH
THE VOLTAGE OF THE
BATTERY.
3,
VOLTAGES AT
PIN
DESIGNATED
**
WILL
VARY
WITH
THE TEMPERATURE OF
THE BATTERY.
4