JVC TM-R14U Service Manual page 2

TM -
R 14 U
SAFETY
PRECAUTION
( 1 }
Dielectric Strength Test
The isolation between the AC primary circuit and all metal
parts
exposed
to
the
user
,
particularly any
exposed metal
part
having a
return
path
to
the chassis should withstand
a
voltage of 1 , 100 V AC (
r
.
m
.
s
.
)
for
a period
of one second
.
Withstand a voltage of 1
,
100 V AC ( r .
m
.
s
.
)
to
an
appliance
rated up
to
120 V , and 3
,
000 V AC ( r
.
m
. s
.
)
to
an appliance rated 200 V or more
,
for a period of one
second
.
This method of
test requires
a
test
equipment
not
generally
found in the service trade
.
(
2
)
Leakage Current Check
Plug the AC line cord
directly into
the AC outlet ( do
not
use
a line isolation transformer during
this check
.
)
.
Using
a " Leakage Current Tester " , measure the leakage
current
from each exposed
metal
part
of the cabinet
,
particularly
any exposed metal
part
having a
return
path
to
the chassis
,
to
a known good earth
ground (
water
pipe ,
etc
.
)
.
Any
leakage
current must not
exceed 0.5 mA AC
( r
.
m
.
s
.
)
.
Alternate Check Method
Plug
the AC line cord directly into the AC outlet
(
do
not
use a line isolation transformer during
this check
.
)
.
Use
an AC voltmeter having
,
1
,
000 ohms
per volt or more
sensitivity in the following
manner
.
Connect a 1
,
50012 10 W
resistor paralleled by
a 0.15 juF AC
-
type
capacitor between
an
exposed metal
part
and
a
known good earth ground
( water
pipe
,
etc
.
)
.
Measure the AC voltage across the resistor with the
AC
voltmeter
.
Move the resistor connection
to
each exposed metal
part
,
particularly any exposed metal
part
having a
return
path
to
the chassis , and
measure the AC voltage across the resistor
.
Now
,
reverse the plug in the AC outlet and
repeat
each
measurement
.
Any voltage
measured
must not
exceed
0.35 V
AC
( r
.
m . s
.
)
.
This corresponds
to
0.5 mA AC (
r
.
m
.
s
.
)
.
1
.
The design of this
product contains special hardware
,
many
circuits and
components specially for safety purposes
.
For continued protection
,
no changes should be made
to
the
original design
unless authorized
in writing by
the
manufacturer
.
Replacement
parts must
be identical
to
those used in the original
circuits
.
Service
should be performed by qualified personnel
only
.
2
.
Alterations of the design or circuitry of receiver should ' not
be
made
.
Any design alterations or
additions will void
the
manu
-
facturer ' s
warranty
and will
further relieve
the manufacturer
of responsibility for personal injury or
property
damage resulting
therefrom
.
3
.
Many electrical and mechanical
parts
in television
sets
have
special safety
-
related characteristics
.
These characteristics are
often
not
evident from visual inspection nor can
*
the protection
afforded
by them necessarily be obtained by using replacement
components
rated for higher voltage
,
wattage
,
etc
.
Replacement
parts
which have
these special safety characteristics are identified
in the
parts
list of Service manual
.
Electrical
components having
such features are identified by shading on the schematics and
by
(
A
) on the parts
list
in
Service manual
.
The use of a sub -
stitute replacement which does
not
have the same safety char
-
acteristics as the recommended replacement
part
shown in
the
parts
list in Service
manual many
create
shock
,
fire
,
or
other
hazards
.
4 .
Use isolation transformer when hot chassis
.
The chassis and
any
sub
-
chassis contrained in
some product are
connected
to
one side of the AC power line
.
An isolation
trans
-
former of adequate capacity
should be inserted between the pro
-
duct and the AC power supply point while performing any
service on some
product when the
HOT chassis is exposed
.
5
.
Don ' t
short between the LIVE side
ground and NEUTRAL side
grounding or EARTH side ground when repairing .
Some model ' s power circuit is partly different
in
the GND
.
The
difference of the GND is shown by the LIVE (
_
L
.
) side GND
,
the NEUTRAL
(
73
Ip
) side GND and
EARTH (
^
) side GND
.
Don '
t
short between the
LIVE
side GND and NEUTRAL side
GND or EARTH side GND and never measure with a
measuring
apparatus
( oscilloscope
etc
.
) the LIVE side GND and NEUTRAL
side GND or EARTH side GND
at the
same time
.
If above
note
will
not
be kept
,
a fuse or any
parts
will be broken
.
6
.
If any repair
has been made
to
the chassis , it is recommended
that the B
*
setting
should be checked or adjusted
( See ADJUST -
MENT OF Bj VOLTAGE )
.
7
.
The high
voltage
applied
to
the picture tube
must
conform with
that specified in Service manual
.
Excessive high voltage
can cause
an increase
in
X
-
Ray emission
,
arcing and possible
component
damage
, therefore
operation
under excessive high voltage condi
-
tions should be
kept
to
a
minimum
,
or should be prevented
.
If
severe arcing occurs
,
remove the AC power immediately and
determine the cause by visual
inspection ( incorrect installation ,
cracked or melted high voltage harness
,
poor soldering
,
etc
.
) .
To maintain the proper minimum level
of soft X
-
Ray emission
,
components
in the high voltage circuitry including the picture
tube
must
be the
exact
replacements or alternatives approvided
by the manufacturer of the complete product
.
8
.
Do
not
check high voltage by drawing an arc
.
Use a high voltage
meter
or a high voltage probe with a VTVM
.
Discharge the
picture tube before attempting meter connection , by connecting
a clip lead
to
the ground
frame and
connecting the other end of
the lead
through a
I 0 kl 2 2 W resistor
to
the anode button
.
9
.
When service is required
, observe the original lead dress
.
Extra
precaution
should be given
to
assure
correct
lead dress in the
high voltage circuit area
.
Where a short circuit has occurred
,
those
components
that indicate evidence
of overheating should
be replaced . Always
use the manufacturer
' s replacement com -
ponents
.
10
.
Isolation Check
( Safety
for Electrical Shock Hazard )
After re
-
assembling the product , always perform an isolation
check on the exposed metal
parts
of the cabinet ( antenna
terminals
, channel selector knobs
,
metal cabinet
,
screwheads
,
earphone jack
, control shafts ,
etc
.
) to be sure the product
is safe
to operate
without danger of electrical shock
.
AC VOLTMETER
( HAVING 1000
H
/ V ,
OR MORE SENSITIVITY )
CQ
0.15
/
uF AC
-
TYPE
O
^
PLACE THIS PROBE
ON EACH EXPOSED
METAL PART
—
wv
— *
1500
S 2
10 W
GOOD EARTH GROUND
11
.
High voltage hold down circuit check
.
After repair of the high
voltage
hold down circuit
,
this
circuit
shall be checked
to operate
correctly
.
See
item
"
How
to
check the high voltage
hold down circuit
"
.
2 ( No
.
5741 )