Play Meter
Issue: 1980 February 01 - Vol 6 Num 2 - Page 6
Know your IC
voltage regulators
TYPI CAL APPLICATI ONS
FIGURE 1
DEVICE
INPUT VOLTAGE
MIN
MAX
OUTPUT
CURRENT
OUTPUT
VOLTAGE
LM 323
7 .5
20
3A
+5V
7805
7
25
1 .5A
+ 5v
7905
-7
-25
1 .5A
-5V
7812
14 .5
30
1 .5A
+ 12V
7912
-14 .5
-30
1.5A
-12V
7815
17 .5
30
1 .5A
+ 15V
7915
-17.5
-30
1 .5A
-15V
7818
21
33
1.5A
+ 18V
7918
-21
-33
1 .5A
-18V
7824
27
38
1.5A
+24V
7924
-27
-38
1 .5A
-24V
Since most computer controlled
games employ l. C. voltage regula -
tors . a working knowledge of these
devices is necessary .
One of the first steps in isolating a
problem in an electronic game is to
check for proper supply voltages .
Failing voltage supply circuits
produce a number of symptoms
ranging from no or intermittent
operatio n in pingames. to "HUM
BARS" (moving dark areas) or
distorted images on video games .
Troubleshooting regulator circuits
consists of these three initial checks :
Input- must be a DC voltage
within the minimum and maximum
specifications of the device (Table I).
with very little AC or ripple present.
Output- a steady regulated DC
voltage within 5 percent of the
specified device .
C ommon - must have a good
electrical connection to ground and
isolated from the input and output
pins .
Referring to Figure 1 (typical
applications) . an open or leaky input
filter capacitor will result in an
unsteady or fluctuating output . A
shorted or open diode in the bridge
rectifier circuit will result in a
decreased DC input voltage. also
affecting the output. If the input
voltage checks out correctly , the fault
lies in the regulator IC itself or the
output filter capacitor .
These package l. C . regulator
devices contain current limiting as
well as thermal shutdown circuitry to
protect the l.C . from overheating. A
malfunction in this internal circuitry
will cause the regulator to shut down
prematurely . This type of breakdown
can be isolated using "Freeze Spray"
directly on the device . If cooling the
regulator returns it to normal opera -
tion. the regulator is faulty and
should be replaced. providing the
current requirement of the load is
within the device's capabilities .
This method of troubleshooting
I. C . power supplies can be utilized on
any electronic system .
Reprinted with permrssron from
Star-Tech Journal. Merchantville,
New Jersey.
voltage regulators
TYPI CAL APPLICATI ONS
FIGURE 1
DEVICE
INPUT VOLTAGE
MIN
MAX
OUTPUT
CURRENT
OUTPUT
VOLTAGE
LM 323
7 .5
20
3A
+5V
7805
7
25
1 .5A
+ 5v
7905
-7
-25
1 .5A
-5V
7812
14 .5
30
1 .5A
+ 12V
7912
-14 .5
-30
1.5A
-12V
7815
17 .5
30
1 .5A
+ 15V
7915
-17.5
-30
1 .5A
-15V
7818
21
33
1.5A
+ 18V
7918
-21
-33
1 .5A
-18V
7824
27
38
1.5A
+24V
7924
-27
-38
1 .5A
-24V
Since most computer controlled
games employ l. C. voltage regula -
tors . a working knowledge of these
devices is necessary .
One of the first steps in isolating a
problem in an electronic game is to
check for proper supply voltages .
Failing voltage supply circuits
produce a number of symptoms
ranging from no or intermittent
operatio n in pingames. to "HUM
BARS" (moving dark areas) or
distorted images on video games .
Troubleshooting regulator circuits
consists of these three initial checks :
Input- must be a DC voltage
within the minimum and maximum
specifications of the device (Table I).
with very little AC or ripple present.
Output- a steady regulated DC
voltage within 5 percent of the
specified device .
C ommon - must have a good
electrical connection to ground and
isolated from the input and output
pins .
Referring to Figure 1 (typical
applications) . an open or leaky input
filter capacitor will result in an
unsteady or fluctuating output . A
shorted or open diode in the bridge
rectifier circuit will result in a
decreased DC input voltage. also
affecting the output. If the input
voltage checks out correctly , the fault
lies in the regulator IC itself or the
output filter capacitor .
These package l. C . regulator
devices contain current limiting as
well as thermal shutdown circuitry to
protect the l.C . from overheating. A
malfunction in this internal circuitry
will cause the regulator to shut down
prematurely . This type of breakdown
can be isolated using "Freeze Spray"
directly on the device . If cooling the
regulator returns it to normal opera -
tion. the regulator is faulty and
should be replaced. providing the
current requirement of the load is
within the device's capabilities .
This method of troubleshooting
I. C . power supplies can be utilized on
any electronic system .
Reprinted with permrssron from
Star-Tech Journal. Merchantville,
New Jersey.
Future scanning projects are planned by the International Arcade Museum Library (IAML).