MSP10
7
INSPECTIONS
A.
Preparation
RL: Non-inductive resistance, 200W or more power
B.
Inspection and Adjustment
1. Muting Operation
When the power switch is turned on, check that the muting operation is cancelled within 3
±
1 seconds and that the
relay turns on.
2. Idling Current
Adjust the VR 302 and 401 so that the voltage obtained between pins 1 and 2 of CN 301 and 401 is 0.7
±
0.15 mV
respectively.
3. Mid-point Potential
When no signal is applied, check to ensure that the DC voltage between the speaker terminals is less than
±
50 mV.
4. Gain
When a 400 Hz sine wave signal is applied to the input terminal, check that the output level is as described in the
following table.
5. Total Harmonic Distortion
When a 400 Hz sine wave signal is applied to the input terminal (LINE1) and the output level at the LF terminal of the
speaker is 29.0 dBu, check that the total harmonic distortion (T.H.D.) is less than 0.1%.
Next, change the input signal to 10 kHz and the output at the HF terminal of the speaker will be 29.0 dBu, check that
the T.H.D. is less than 0.1%.
When the input terminal is connected with 600 ohm, check that the noise level is as described in the table below. Use
an IHF-A filter for the noise meter (measurement will not be affected by inductive noise).
7. Frequency Response in the Normal State (trim switch at “0”)
Use the output voltage obtained at the LF terminal when a 1 kHz, -20 dBu sine wave signal is input as a reference
(0dB), and change the input frequency to check that the frequency response at the LF and HF terminals vary
accordingly as shown in the table below.
Load resistance
Speaker terminal
Wo (CN504: 4-3PIN)
RL = 4W
Tw (CN504: 1-2PIN)
RL = 8W
Knob
SENSITIVITY
MAX (-6 dB)
TRIM
LOW
0
HIGH
0
LOW CUT
OFF
SPEAKER LF
less than -76 dBu
SPEAKER HF
less than -71 dBu
SPEAKER LF
less than -75 dBu
SPEAKER LF
less than -69 dBu
Input frequency (Hz)
Output terminal LF
Output terminal HF
100
+5.5 +/- 1.2 dB
-
1k
0 dB
-
2k
-5.0 +/- 1.0 dB
-5.0 +/- 2.5 dB
10k
-
+5.5 +/- 2.0 dB
Input terminal
Input level
Speaker LF terminal
LINE IN
XLR balanced
-10 dBu
+16.6 dBu +/- 2 dB
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