Harman Kardon CD491 - Page 3

LEAKAGE TEST
Before returning the unit to the user, perform the following safety checks:
1. Inspect all lead dress to make cer-
tain that leads are not pinched or
that hardware is not lodged be-
tween the chassis and other metal
Parts in the unit.
2. Be sure that any protective devices
such as nonmetallic control knobs,
insulating fishpapers, cabinet backs,
adjustment and compartment cov-
ers or shields, isolation resistor-
capacity networks, mechanical in-
sulators, etc. which were removed
for servicing are properly reinstalled.
3. Be sure that no shock hazard exists; check for leakage
current using Simpson Model 229 Leakage Tester,
standard equipment item No. 21641, RCA Model
WTS540A or use alternate method as follows:
Plug the AC line cord directly into a 120-volt AC
receptacle (do not use an Isolation Transformer for
this test). Using two clip leads, connect a 1500 ohm,
10-watt resistor paralleled by a 0.15mf capacitor, in
series with all exposed metal cabinet parts and a
known earth ground, such as a water pipe or conduit,
Use a VTVM or VOM with 1000 ohms per volt, or
higher, sensitivity to measure the AC voltage drop
across the resistor. (See Diagram.) Move the resistor
connection to each exposed metal part having a
return path to the chassis (antenna, metal, cabinet,
screw heads, knobs and control shafts, escutcheon,
etc.) and measure the AC voltage drop across the
resistor. (This test should be performed with the
power switch in both the On and Off positions.)
A reading of 0.35 volt RMS or more is excessive and
indicates a potential shock hazard which must be
corrected before returning the unit to the owner.
Dolby* HX-Professional Headroom Extension
(HX-PRO) System
The CD491 is equipped with the Dolby HX-Professional
Headroom Extension system (HX-PRO). It operates only
during the record mode and does not require the user to
“turn it on” or make adjustments. It is compatible with
any low noise (standard), chromium dioxide (CrO2), or
metal audio cassette tape.
The effect of HX-PRO is that is extends the high fre-
quency saturation (overload) level of the tape being
recorded. Therefore, many of the high level, high fre-
quency music signals that would be compressed or
distorted with a conventional cassette deck will be
recorded accurately by the CD491.
ae advantages of HX-PRO are:
1. The performance of low noise and chromium dioxide
tapes almost equals that of the more expensive metal
tapes.
A major improvement is made in high frequency
dynamic range.
3. The higher record levels result in an increased signal-
to-noise ratio.
4. No decoding is necessary. The improved recording
accuracy can be appreciated with any high quality
tape player, including a portable or car stereo unit.
5. It can be used with or without Dolby B and C noise
reduction circuitry.
N
TO EACH EXPOSED
METAL SURFACE OF
UNIT UNDER TEST
TO EXPOSED
METAL PARTS
Response (dB)
—40
1000 20005000 10000-20000 50000
SIMPSON MODEL 229 ETC, FOR
LEAKAGE TEST
TO AC GROUND SUCH
AS WATER OR GAS PIPE,
HIGH
BX
CABLE,
CONDUIT,
ETC.
VOLTAGE
OR +LEAD
LEAD
OAC SCALE O
0.15 MF
TEST PROBE
CONNECT TO KNOWN
EARTH GROUND
Hx-PAOs Day CON!
J
HXPROON, Dowy COFF
WXPRO & Dolby C OFF
Frequency (Hz)
Frequency Response |
“Noise reduction and headroom extension manufac- {
tured under license from Dolby Laboratories Licensing
Corporation. HX Professional originated by Bang and
Olufsen. “Dolby” and the double-D symbol are trade-
marks of Dolby Laboratories Licensing Corporation.