Zenith SM-ZVM-122 Service Manual page 2

II
PRODUCT SAFETY SERVICING GUIDELINES
CAUTION: Do not attempt to modify any circuit.
Perform service work only after you are thoroughly
familiar with all of the following safety checks and
servicing guidelines. To do otherwise increases the
risk of potential hazards and injury to the user. CAU-
TION: Never attempt to service a chassis that is con-
nected directly to an AC line. Make sure
it
is con-
nected through an isolation transformer. No matter
which way the AC plug is inserted, a potential
shock hazard is present at chassis ground unless
you use an isolation transformer during servicing.
Since one side of the AC input is fused; there's a
50%
chance you'll blow a fuse, or a
50%
chance
you'll destroy components and/or test equipment
without an isolation transformer. The chassis con-
sists of a single circuit board mounted horizontally
in the bottom of the cabinet. All circuit parts are
mounted on the board except the CRT and deflection
yoke. The horizontal sweep transformer is also
mounted on the chassis circuit board. You can slide
the board out of the cabinet without disconnecting
it, and the Monitor will operate with the board ex-
posed. Screws are not required to hold the board
in place. It slides into slots which are molded into
the cabinet, and the cabinet back holds it in place.
SAFETY CHECK
After the original service problem has been cor-
rected, check for the following:
FIRE
&:
SHOCK HAZARD
1.
Be sure that all components are positioned in
such a way to avoid the possibility of adjacent
component shorts. This is especially impor-
tant on those chassis which are transported
to and from the repair shop.
2.
Never release a repair unless all protective de-
vices such as insulators, barriers, cover
shields, strain reliefs, and other hardware
have been reinstalled per the original design.
3.
Inspect the soldering for possible cold solder
joints, frayed leads, damaged insulation (in-
cluding AC cord), solder splashes or sharp
solder points. Remove all loose foreign parti-
cles.
4.
5.
6.
Check "across-the-line" capacitors and other
components for physical evidence of damage
or deterioration, and replace them if neces-
sary. Follow the original layout, lead length,
and dress.
No lead or component should touch a receiv-
ing tube or a resistor rated at
1
watt or more.
Avoid lead tension around protruding metal
surfaces.
Always replace critical components (shaded
on the Schematic Diagram and parts lists)
such as: fuses, flameproof resistors,
capacitors, etc. with exact Zenith types. Do
not use replacement components other than
those specified or make unrecommended cir-
cuit modifications.