Canon Canovision8 E50E Service Manual page 2

SAFETY PRECAUTIONS
The following precautions should be observed when servicing.
1,
Since many parts in the unit have special safety-related characteristics, always use
genuine CANON replacement parts.
Especially critcal parts in the power circuit block should not be replaced with other
makes,
Critical parts are marked with A\ in the schematic diagrams.
The primary source of X-ray radiation in this viewfinder is the picture tube. The cube
used in the viewfinder is especially constructed to limit X-ray radiation emission.
For continued X-ray radiation protection, the replacement tube must be same type as
the original, CANON approved one.
When servicing, observe the original lead dress. If a short circuit is found, replace
all parts which have been oberheated or damaged by the short circuir.
After servicing, see to it that all the protective devices such as insulation
barriers, insulation papers shields are properly instalied.
After servicing, make the following leakage current checks to prevent the customer
from being exposed to shock hazards.
5-1 Leakage Current Cold Check
1) Unplug the AC cord and connect a jumper between the two prongs on the plug.
2) Measure the resistance value, with an ohmmeter, between the jumpered AC plug and
each exposed metalic cabinet part on the equipment such as screwheads,
connectors, control shafts, etc. When the exposed metalic part has a return path
to the chassis, the reading should be between 1M2 and 5.2M%. When the exposed
metal does not have a return path to the chassis, the reading must be %
~ 5-2 Leakage Current Hot Check
1) Plug the AC cord.directly into the AC outlet. Do not use an isolation
transformer for this check.
2) Connect a 1.5KS 10 watt resistor, paralleled by 0.15yF capacitor, between each
exposed metalic parts on the unit and a good earth ground such as a water pipe,
as shown in figure 1.
3) Use an AC voltmeter, with 10002 volt or more sensitivity, to measure the
potential across the resistor.
4) Check all exposed metallic parts of the cover (Cable connection, Handle bracket,
metallic cabinet. Screwheads, Metallic overlays, etc), and measure the voltage
at each point.
5) Reverse the AC plug in the AC outlet and repeat each of the above measurements.
6) The potential at any point should not exceed 0.75V RMS.
A leakage current tester (FLUKE MODEL: 8000A equivalent) may be used to make the
hot checks.
Leakage current must not exceed 0.5 nilliamp.
In case a measurement is out side of the limits specified, there is a
possibility of a shock hazard, and corrective action must be taken before
returning the instrument to the customer.
AC VOLTMETER
Water pine
(€anh-Ground)
AC OUTLET Figure 1. Leakage Current Hot Check