Alto MC700.4, Service Manual

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MC 700.4 TEST PROCEDURES
1. INSTRUMENTS
1). Power source 2). VOM meter 3). VP-7724A audio precision 4). Oscillograph
5). Two load resistors with 4O(1000W) 6). AC protector
2.
TEST PROCEDURES
1) Set all the dip switches to the position OFF and VR of CH1/CH2 (or CH3/CH4) to MAX. When the power
switch is turned on, the blue power indicator lights up. PROT indicator lights up red. After 2-5 seconds, it
turns green.
2) Connect 4O load with output terminal and input 5KHz signal to CH1/CH2/CH3/CH4. Adjust signal level
for about 5Vp -p (approximately 2VRMS) output. Adjust R1-16(CH1) /R2-16(CH4) (note: adjust R3
MC700SVR board for CH2 and CH3) for the purpose that there is no cross distortion of the wave on
oscillograph. Increase output signal level for the purpose that the wave distortion is 2-3%. Adjust R1-20
，
R1-21(CH1) and R2-20
，
R2-21(CH4) for the purpose that the point of output cross distortion is on the peak
of wave. (note: keep the power voltage 230V). After the test, check the angle of VR. It should correspond
to the angle which is in the production manual.
3) Following step 2, input 1KHz
，
-3.9dB(1.210V
±
0.1V) signal, and the output should be 51V+/1V. At this
time, the distortion should be less than 1%. When VR is being turned
，
LEVEL indicator in turn from
-20dB
、
-10dB. When it gets to CLIP, the wave is distorted.
4) Short circuit the output terminal when the output gets max. At this time, the power consumption is less
than 350W.
5) S/N is more than 90dB( weighted is more than 100dB).
6) LIMITER test
：
Switch the dip switch as CLIP LIMIT sign on chassis, input 1KHz/ +10dB, and turn VR
to max, then LIMIT indicator on the front panel lights up, (CH1/CH2/CH3/CH4) output signal has no
clip.
7) Input signal 1KHz/0dB to CH1/CH3, not to CH2/CH4. Set VR of CH2 to max. CH2/CH4 have no signal
output. Switch the dip switch as PARALLEL MODE sign. PAR indicator on the front panel lights up. Turn
VR of CH2/CH4, output wave of CH2/CH4 is visible.
8) Switch the dip switch as the FILTERS sign to the position FILTER ON and the position 75Hz FILTER.
Turn TIME/DIV knob of the oscillograph to the position 10ms and input 125Hz/0dB signal, then adjust
VR and input signal for the purpose that the output is 5dB. Set the input signal to 75Hz and the wave
become smaller. At this time the output is 2dB
±
0.5dB. Set input signal to 125Hz again and switch to 35Hz
FILTER position, then set input signal to 35Hz. The wave become smaller. At this time the output is 2dB
±
0.5dB. Refer to the attached frequency response figure.
9) Switch the dip switch as RIDRE MONO sign, BRDG indicator on the front panel lights up. Input 1KHz,
-4.5dB(1.195V
±
0.1V) signal from CH1(CH3) ( set CH2/CH4 VR to min). Connect 8
Ω
load to the output
terminal and output 100
±
1V voltage. At this time distortion is less than 1% .
10)
Turn off the input signal, and the standby power consumption is less than 85W.
05-1