
SW500
14
1. Measuring instruments
Oscilloscope, Level meter, Noise meter (with a DIN audio filter),
Distortion rate meter, Wattmeter, Noninductive load resistance
4 Ωx 2 (power capacity: beyond 500W)
2. Preparation
1) LEVEL: MAX
CUTOFF FREQ.: MIN (80Hz)
PHASE SW: NORM
2) Connecting the measuring instrument: Float the ground and
then connect the measuring instrument to the midpoint of the
noninductive load resistance (4 Ωx 2).
6) Output noise level
Ground the [INPUT A and B] terminals with 600 Ωof
resistance, measure the noise level of the output terminal,
and then check that the maximum noise level is –65 dBu or
less.
In addition, measure the noise level from [OUTPUT HIGH
PASS Aand B] with balance and check that it is –90 dBu or
less. Use a DIN audio filter with the noise meter.
7) Frequency response
When a 20 Hz, 30 Hz, 50 Hz, or 100 Hz (-20 dBu) signal is
input into the [INPUT A] terminal and the 30 Hz and –20
dBu input time of the output voltage is the standard (0 dB),
check that the frequency response is as shown in the
following table.
Measure the frequency response with the [CUTOFF FREQ.]
at 100 Hz (MAX) and 80 Hz (MIN).
INSPECTIONS
Floating ground
4Ω
1
CN203
CN203
44Ω
Amplifier
Measuring
instrument
*Disconnect the connector assembly connected with the
speaker from CN203.
3. Checks and adjustments
1) Muting operation
When turning the power switch on, check that the muting
operation is cancelled within 3 ±1 seconds and that the relay
turns on. In addition, check that the power indicator turns on.
2) Adjusting the idling current
Adjust the VR201 and VR202 so that the voltage obtained
between pins 1 and 2 of AMP PCB CN206 and CN207 is
1 ±0.2 mV respectively.
3) Mid-point potential
When no signal is applied, check that the DC voltage of AMP
PCB CN203 (VH4P) is ±100 mV or less.
4) Gain/Efficiency
When a 50 Hz, 0 dBu signal is input into [INPUT A and B]
terminals with an output voltage of +28.3 ±1 dBu, check that
the primary power consumption is 410 ±50W. (Be sure to check
both [INPUTA] and [INPUT B] terminals.) In addition, check
that the output voltage of the [OUTPUT THRU A and B]
terminals is 0 ±1 dBu.
When a 1 kHz, 0 dBu signal is input into the [INPUTA and B]
terminals, check that the output voltage of the [OUTPUT HIGH
PASS A and B] terminals is 0.2 ±0.5 dBu. (Be sure to apply a
600 Ωload with balance when performing this measurement.)
5) Total harmonic distortion rate
When a 100 Hz signal is input into the [INPUT A] terminal
and the output voltage is 32.2 dBu, check that the total harmonic
distortion rate is THD + N = 1% or less.
8) PHASE switch
When the [PHASE] switch is set to REV, check that the phase
changes by 180 degrees to accommodate the input signal.
9) Protection circuit
When DC +5 V(power output resistance = 10 kΩ) is applied
between pins 1 and 2 of AMP PCB CN209, check that the
relay turns off within 1 second.
In addition, when the input signal is cut, check that the signal
automatically returns within 10 seconds.
10) Clip indicator
When a 50 Hz, +4.3 dBu signal is input into the [INPUTA]
terminal, check that the red LED is on.
4. Checking after assembly
1) When a 20–500 Hz, 0.1 Vrms (-17.8 dBu) sine wave are
input into the [INPUTA] terminal, check that no abnormality
occurs, such as voice coil contact, air leakage, and vibration.
In addition, when each knob is moved, check that the sound
volume and quality vary smoothly and that no noise is
produced.
2) Speaker output phase
Check that the output is in positive phase with respect to the
input.
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TEL 13942296513 QQ 376315150 892498299
TEL 13942296513 QQ 376315150 892498299
http://www.xiaoyu163.com
http://www.xiaoyu163.com