Safety Precautions - Sherwood R-772 Service Manual

WARNING
Before servicing this unit, familiarize yourself with the following precautions:
1. Many electrical and mechanical parts in this
chassis have special safety characteristics that
often pass unnoticed and the protection
afforded by them cannot necessarily be
obtained by using replacement components
rated for higher voltage, wattage, etc.
Replacement parts that have these special
safety characteristics are identified in this
manual and its supplements: electrical
components having such features are identified
by in the schematic diagram and the parts
list.
Before replacing any of these components,
read the parts list in this manual carefully. The
use of substitute replacement parts that do not
have the same safety characteristics as
specified in the parts list may create shock, fire,
or other hazards.
2. Before returning the set to the customer,
always do an AC leakage current check on the

SAFETY PRECAUTIONS

1
exposed metal parts of the cabinet, such as
terminals, screw heads, and metal overlays, to
be sure the set is safe to operate danger of
electrical shock. Plug the AC line cord directly
into a 120 V AC outlet(USA Version) or 230 V
AC outlet(EU Version). (Do not use a line
isolation transformer during this check.) Be sure
your AC voltmeter has a sensitivity of 5000 Ω
per volt or greater. Then connect a 1500 Ω 10
watt resistor, paralleled by a 0.15 µF 150 V AC
capacitor, between a known good earth
ground(such as a water pipe, or conduit) and
the exposed metallic parts, one at a time.
Measure the AC voltage across the combination
of a 1500 Ω resistor and a 0.15 µF capacitor.
Reverse the AC plug at the AC outlet and
repeat AC voltage measurements for each
exposed metalic part. Voltage measured must
not exceed 0.75 V RMS. This corresponds to
0.2 mA AC. Any value exceeding this limit
constitutes a potential shock hazard and must
be corrected immediately.