Zenith ZVM-121 Service Manual page 5

3.
It
is essential that the serviceman have an accu-
rate high voltage meter available at all times.
Check the calibration of this meter periodically
against a reference standard, such as the one
available at your distributor.
4.
When the high voltage circuitry is operating
properly, there is no possibility of an
X-radiation problem. Every time you service a
monochrome chassis, run the brightness up and
down while you monitor the high voltage with a
meter to be certain that the high voltage does not
exceed the specified value and that it is regulat-
ing correctly. We suggest that you and your ser-
vice organization review test procedures so that
voltage regulation is always checked as a stan-
dard servicing procedure, and that the reason
for this prudent routine be clearly understood
by everyone. It is important to record an accu-
rate high voltage reading on each customer's
invoice.
5.
When you are troubleshooting and making test
measurements in a Monitor with a problem of
excessive high voltage, avoid being unnecessar-
ily close to the picture tube and the high voltage
compartment. Do not operate the chassis longer
than is necessary to locate the cause of excessive
voltage.
6.
Models which use a high voltage rectifier
vacuum tube should have that tube replaced
only with a Zenith recommended replacement
type or a Zenith recommended solid-state
rectifier replacement. The high voltage
compartment and all metal shields, where used,
must be kept in place whenever the chassis is
operating. If a shield is missing, it should be
replaced at once as a standard servicing
procedure.
Page
1-3
TIPS ON PROPER INSTALLATION
1.
Never install a Monitor in a closed-in recess,
cubbyhole, or closely fitting shelf space.
2.
Never install a Monitor over or close to a heat
duct, or in the path of heated air flow.
3.
Avoid conditions of high humidity such
as: outdoor patio installations where dew is a
factor, or near steam radiators where steam leak-
age is a factor.
4.
Avoid placement where draperies may obstruct
rear venting. Customers should also avoid the
use of decorative scarves or other coverings
which might obstruct ventilation.
5.
Wall and shelf-mounted installations must use
the factory approved mounting kit and mount-
ing instructions.
6.
A Monitor mounted to a shelf or platform must
retain its original feet or the equivalent thick-
ness in spacers for adequate air flow from the
bottom. Bolts or screws used for fasteners must
not touch any parts or wiring. Perform leakage
tests on customized installations.
7.
Caution customers against the use of a Monitor
on a sloping shelf or in a tilted position, unless it
is properly secured.