NAD T 751 Service Manual page 5

SAFETY CHECK AFTER SERVICING
Examine the area surrounding the repaired location for damage or deterioration. Observe that screws, parts and
wires have been returned to original positions. Afterwards, perform the following tests and confirm the specified
values in order to verify compliance with safety standards.
• Insulation resistance test
confirm the specified insulation resistance or greater between power cord plug prongs and externally exposed
parts of the set (RF terminals, antenna terminals, video and audio input and output terminals, microphone
jacks, earphone jacks, etc.) See table below.
• Dielectric strength test
Confirm specified dielectric strength or greater between power cord prongs and exposed accessible parts of
the set (RF terminals, antenna terminals, video and
audio input and output terminals, microphone jacks,
earphone jacks, etc.) See table below.
• Clearance distance
When replacing primary circuit components, confirm
specified clearance distance (d), (d') between sol-
dered terminals, and between terminals and sur-
rounding metallic parts. See table below.
Table 1 : Ratings for selected areas
AC Line Voltage
*200 to 240 V
*100 to 130 V
* Class II model only.
Note. This table is unofficial and for reference only. Be sure to confirm the precise values for your particular
country and locality.
• Leakage Current test
Confirm specified or lower leakage current between B(earth ground, power cord plug prongs) and externally
exposed accessible parts (RF terminals, antenna terminals, video and audio input and output terminals, micro-
phone jacks, earphone jacks, etc.)
Measuring Method: (Power ON)
Insert load Z between B(earth ground, power cord
plug prongs) and exposed accessible parts. Use an
AC voltmeter to measure across both terminals of
load Z. See figure and following table.
Table 2:Leakage current ratings for selected areas.
AC Line Voltage
200 to 240 V
100 to 130 V
Note. This table is for IEC member only. Be sure to confirm the precise values for your particular country and
Note. locality.
Insulation
Region
Resistance
Europe
F 10 MΩ/500 V DC
Australia
Load Z
Region
Europe
Australia
Chassis
Dielectric
Strength
4kV 1 minute
Exposed
accessible
part
Load
Leakage Current(i)
i E 0.7m A peak
2k Ω
i E 2m A DC
i E 0.7m A peak
50k Ω i E 2m A DC
1-4
d
Primary circuit terminals
a
Fig. 2
Clearance
Distance(d),(d)
F 6mm(d)
F 8mm(d)
(a Power cord)
Z
AC Voltmeter
Earth Ground,
Power cord plug prongs
B
Fig. 3
Earth Ground
(B) to :
Antenna earth
terminals
Other terminals