c) Connect an oscilloscope to power amplifier output (connect for the
speaker).
d) Adjust volume to minimum.
e) Use the oscilloscope to measure peak-to-peak voltage, in Volt peak-to-peak
(Vpp).
Minimum Nominal Maximum Unit
- 25 500 mVpp
3.1.3 Audio frequency response in TV’s without tone control
a) TV setup in “PP” condition.
b) Connect a color bar generator (PAL-M system) to video-in.
c) Connect to the audio input TV - an audio generator adjusts to 500 mVac
level, and sine wave 1kHz.
d) Connect to the output power amplifier a resistive load with the same value
of the impedance speaker.
e) Connect an AC voltmeter over the resistive load and adjust volume control
until obtain 1 Vac).
f) Realign the audio generator to 100 Hz sine wave at the same level (500
mVac).
g) Read the new voltage in the resistive load and calculate the change in dB
through next equation:
A
(100Hz)
=20 log(V
LF
/V
REF
)
The result is defined in “Decibel units “
h) Readjust the audio generator frequency to 10 kHz at the same level.
i) Read the new voltage Vh at the resistive load and calculate the change in
dB through the next equation:
A
(10kHz)
=20log(V
HF
/V
REF
)
Condition Minimum Nominal Maximum Unit
100Hz -4,00 0,00 +2,00 dB
10kHz -5,00 -1,00 +3,00 dB
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