Zenith SM-ZVM-122 Service Manual page 4

IV
3.
4.
5.
6.
It is essential that the serviceman have an ac-
curate 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.
When the high voltage circuitry is operating
properly, there is no possibility of an X-radia-
tion 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 regulating correctly. We suggest that you
and your service organization review test pro-
cedures so that voltage regulation is always
checked as a standard servicing procedure,
and that the reason for this prudent routine
be clearly understood by everyone. It is im-
portant to record an accurate high voltage
reading on each customer's invoice.
When you are troubleshooting and making
test measurements in a Monitor with a prob-
lem of excessive high voltage, avoid being un-
necessarily 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.
Models which use a high voltage rectifier vac-
uum tube should have that tube replaced only
with a Zenith recommended replacement
type or a Zenith recommended solid-state rec-
tifier replacement. The high voltage compart-
ment 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 pro-
cedure.
TIPS ON PROPER INSTALLATION
1.
Never install a Monitor in a closed-in recess,
cubbyhole, or closely fitting shelf space.
2.
3.
4.
5.
6.
Never install a Monitor over or close to a heat
duct, or in the path of heated air flow.
Avoid conditions of high humidity such as:
outdoor patio installations where dew is a fac-
tor, or near steam radiators where steam leak-
age is a factor.
Avoid placement where draperies may
obstruct rear venting. Customers should also
avoid the use of decorative scarves or other
coverings which might obstruct ventilation.
Wall and shelf.mounted installations must
use the factory approved mounting kit and
mounting instructions.
A Monitor mounted to a shelf or platform
must retain its original feet or the equivalent
thickness in spacers for adequate air flow
from the bottom. Bolts or screws used for fas-
teners must not touch any parts or wiring. Per-
form leakage tests on customized installa-
tions.
7.
Caution customers against the use of a Moni-
tor on a sloping shelf or in a tilted position,
unless it is properly secured.
DISCIIAJlGING THE CRT
Discharge the high voltage lead going to the anode
of the CRT. One method of discharging it is to use
a screwdriver and a
12"
jumper wire with an alligator
clip on each end. Clip one alligator clip to chassis
or DAG ground, and place the other one on your
screwdriver. Then slide the end of the screwdriver
under the high voltage cap at the anode of the CRT.