Tuesday, December 22, 2015

YAMAHA CP2000 power amplifiers adjustments and Power amp circuit

Contents of this article 

  • Idle current adjustment 
  • Output noise level 

YAMAHA CP2000 

Adjustments 
Fan and temperature indicator
The fan shall operate when the two jumper wires inside the frame marked FAN-C inside sheet IN are shorted. Next, the temperature indicator shall come on when the two jumper wires inside the frame marked TM-C are shorted. (Refer to the figure to the right for FAN-C, TM-C.)
Power on muting time
At t=2.5 ± 1 seconds after the power switch is turned on, the muting shall be cancelled and the protection indicator shall go off.
Idling current
Ground the input terminal and adjust VR101 (L ch) and VR102 (R ch) so that the CN108 (L ch) and CN107 (R ch) No. 1 and 2 terminals show DC voltage of Vb=0.5 ± 0.1 mV.
Once all inspections have been completed, re-inspect Vb and adjust so that it is Vb=0.5 ± 0.1 mV.
Output terminal DC voltage
Ground the input terminal and measure the Vdc (direct current voltage) of the output terminal. It shall be Vdc=0 ± 75 mV.
Gain
An output voltage of +24.0 ± 0.5 dBu shall be attained when 1 kHz, -10.0 dBu sine wave is input to the input terminal.
This inspection shall also be performed in the PARALLEL mode.
Frequency characteristics
* YAMAHA SPEAKER PROCESSING OFF:
Using 1 kHz as a standard for the output voltage, the output voltage shall be within -0.5 ± 0.5 dB at 20 kHz when 20 Hz, 1 kHz,
20 kHz, -10 B dBu sine waves are input to the input terminal.
* YAMAHA SPEAKER PROCESSING ON:
Using 1 kHz as a standard for the output voltage, with the Yamaha speaker processing off, the output voltage shall be within + 6.5 ± 1.5 dB when a 70 Hz, -10 dBu sine wave is input to the input terminal.
Total harmonic distortion ratio characteristics
The total harmonic distortion ration shall be THD=1 % or less when a 1 kHz high definition sine wave is input to the input terminal and the rated output of 650 w + 650 w / 4 ohm (36.4 dBu/ch) has been attained. This inspection shall be completed within 30 seconds.
Channel separation load resistance 8 Ω
When the input terminal for one of the channels has attained a 1kHz, -5dBu sine wave has and that input terminal is grounded by the introduction of 600 Ω resistance, the measured output voltage of the other channel shall by -70 dB or less, using a output voltage with (0 dB) as the reference level.
Output noise level
Measure the noise level at the output terminal when the input attenuator has been set to MAX and a input terminal has been grounded by the introduction of a 600 Ω resistance. It shall be -67 dBu or less. Next, set the input attenuator to MIN and measure. It shall be -70 dBu or less.
Stability
The following conditions shall be met when a 10 kHz, -10dBu rectangular pulse is input and a capacitance of 10 pf ~ 0.47 µF is connected in parallel with a load resistance of 4 Ω. Overshoot Vp/Vo 1.8
Ringing: Within 5 waves
Next, when there is only a pure capacitance of 10 pf ~ 0.47 µF the following conditions shall be met.
Vp/Vo 2.5
Ringing: There shall be convergence within 7 waves and no oscillation, etc.
Protection circuit
The protection circuit shall operate and the relay shall not open when a 10 Hz, +5.4 dBu sine wave is input and the output wave is made to clip. Next, the protection circuit shall operate within two seconds and break the output when a 1 Hz, 0.0 dBu sine wave is input. In addition, when the input signal is cut, it shall automatically recover within 10 seconds.
Efficiency
(1) The primary electrical power shall be measured and be within the range shown below when a 1 kHz, -6.6 dBu sine wave is input to the input terminal.
330 W ± 50 W (U: 4.0 A ± 0.6 A, H: 2.0 A ± 0.3A)
(2) The primary electrical power shall be measured and be within the range shown below when the input terminal is grounded by the introduction of the input terminal.
25 W ± 10 W (U: 0.33 A ± 0.13 A, H: 0.20 A ± 0.08 A)
PC limiter and comp
Input a 1 kHz, -1.5 dBu sine wave to the input terminal and connect 1 Ω (± 5 %) as a load to the output terminal. Under these conditions, a 10 V Vrms 16 V sine wave shall be attained at the output. The total harmonic distortion ratio shall be THD=5 % or less.
Also at this time, the clip indicator shall come on. This inspection shall be completed within 30 seconds.
Signal indicator
The green signal indicator shall come on when a 1 kHz, -23 dBu sine wave is input.
In addition, the green and yellow signal indicators shall come on when a 1 kHz, -4 dBu sine wave is input.
Inspection
Gain
An output voltage of +24.0 ± 1.0 dBu shall be attained when a 1 kHz, -10 dBu sine wave is input to the input terminal.
Frequency characteristics
Using 1 kHz as a standard for the output voltage, the output voltage shall be within -0.5 ± 0.5 dB at 20 kHz when 20 Hz, 1 kHz, 20 kHz, -10 B dBu sine waves are input to the input terminal.
Total harmonic distortion ratio characteristics
The total harmonic distortion ration shall be 1 % or less when a 1 kHz high definition sine wave is input to the input terminal and the output voltage of 36.4 dBu has been attained. This inspection shall be completed within 30 seconds.
Output noise level
Measure the noise level at both terminals of the load resistance when the input attenuator has been set to MAX and the input terminal has been grounded by the introduction of a 600 Ω resistance. It shall be -60 dBu or less. Next, set the input attenuator to MIN and measure. It shall be -60 dBu or less.
Process after completion of inspection
Close up the input attenuator in a half-clockwise direction.
Set YAMAHA SPEAKER PROCESSING to on.
Set the mode switch to STEREO.
Others
A DIN audio filter shall be used for the measurement of the noise level.
0 dBu=0.775 V
POWER AMPLIFIER CIRCUIT 
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