Wednesday, December 02, 2015

YAMAHA XP7000 – XP5000 POWER AMPLIFIER INSPECTION ADJUSTMENTS AND CIRCUIT DIAGRAM

Contents of this article 
  • Idle current adjustments 
  • Protection circuit 
  • Test preparation 

POWER AMPLIFIER 

YAMAHA XP7000 – XP5000 

TEST ADJUSTMENTS AND CIRCUIT DIAGRAM 

TEST AND INSPECTION 
Preparation for STEREO/PARALLEL mode
Attenuator : “0” (MAX) (both channels)
Input terminal : XLR connector 2PIN-HOT/3PIN-COLD/1PIN-GND
MODE switch : STEREO
GAIN switch : 32 dB
HPF switch : OFF (both channels)
Load resistance : 8 ohms +/- 1%
# Unless otherwise specified, use above settings for all inspection items of the STEREO/PARALLEL mode. When any setting
has been changed, be sure to reset it back to the above setting before testing other items.
# Unless otherwise specified, use a high grade sine wave for the input signal.
# Unless otherwise specified, keep both channels in the drive mode.
# The unit used for analog I/O level is 0 dBu=0.775 Vrms.
Inspection and Adjustment
Power ON muting time and POWER LED, PROTECTION LED
Turn on the power and check that POWER and PROTECTION LEDs light up.
Turn on the power and check that PROTECTION LED turns off in 2.5 ± 1 seconds.
Fan and TEMP LED
Short-circuit 2 jumper cables within the “FAN-C” marked frame on the PS circuit board and check that the fan runs. Also shortcircuit 2 jumper cables within the “TM-C” marked frame and check that TEMP LED lights up.
Idling current
Ground the input terminal and adjust VR201 so that the DC voltage Vb between the pins 1 and 2 of CN101 on the PA unit becomes 0.275 ± 0.025 mV. After all inspections, adjust the Vb again so that it becomes 0.5 ± 0.1 mV. Perform this adjustment on both channels.
DC voltage of output terminal
Ground the input terminal and measure the DC voltage Vdc at the output terminal. Check that the measured value is 0 ± 75 mV.
Gain
Nominal gain
Input a 1 kHz, -10.0 dBu sine wave signal to the input terminal and check that +22.0 ± 0.5 dBu output voltage is obtained.
GAIN switch
Set the GAIN switch to 26 dB.
Input a 1 kHz, -10.0 dBu sine wave signal to the input terminal and check that +16.0 ± 0.5 dBu output voltage is obtained.
Next, set the GAIN switch to +4 dBu.
Input a 1 kHz, -10.0 dBu sine wave signal to the input terminal and check that the output voltage obtained is as  below.
XP7000
+25.7 +/- 0.5 dBu
XP5000
+24.2 +/- 0.5 dBu
Attenuator
With the attenuator set to the -10 dB position, input a 1 kHz, -10.0 dBu sine wave signal to the input terminal and check that an output voltage within +12.0 ± 3.0 dBu is obtained.
PARALLEL mode
Set the MODE switch to PARALLEL.
Input a 1 kHz, -10.0 dBu sine wave signal to the input terminal of the A channel and check that +22.0 ± 0.5 dBu output voltage is obtained for both channels.
Do not input any signal to the input terminal of the B channel.
Frequency characteristics
Input 20 Hz, 1 kHz, 20 kHz, -10 dBu signals and check that the output voltage obtained is within -0.5 ± 0.5 dBu at 20 Hz and 20 kHz as compared with the output voltage at 1 kHz.
<Set the HPF switch to 20 Hz>
Input a 20 Hz, -10 dBu signal and check that the output voltage is within -3.0 ± 2.0 dBu as compared with the output voltage at 1 kHz, -10 dBu in the HPF OFF state.
<Set the HPF switch to 55 Hz>
Input a 55 Hz, -10 dBu signal and check that the output voltage is within -3.0 ± 2.0 dBu as compared with the output voltage at 1 kHz, -10 dBu in the HPF OFF state.
Distortion
Input 20 Hz, 20 kHz signals to the input terminal and check that the distortion is 0.1% or less when the rated output as specified in the table below is obtained.
This inspection should be completed within 30 seconds.
XP7000 (U/T/A)
74.82 V
(700 W + 700 W)
XP7000 (H/B/K/O)
72.12 V
(650 W + 650 W)
XP5000
63.25 V
(500 W + 500 W)
Channel separation
Input a 1 kHz signal to the A channel and shunt 2 pin (hot) and 3 pin (cold) of input terminals of the B channel with 600 ohms. Set the output of the A channel as specified in “Output level of the channel with signal input” section in the table below. Check that the output voltage of the B channel is less than the value specified in “Output level of the channel terminated” section in the table below. Reverse A and B channels and perform the same check. Use a DIN AUDIO filter for this measurement.

XP7000
XP5000
Output level of the channel
with signal input
36.7 dBu
(350 W)
35.3 dBu
(250 W)

Output level of the channel
terminated

-33.3 dBu

-34.7 dBu
 Output noise level
Shunt 2 pin (hot) and 3 pin (cold) of input terminals with 600 ohms. Measure the noise level at the output terminal and check that it is -65 dBu or less. Set the attenuator to MIN and check that the noise level is -70 dBu or less. Use a DIN AUDIO filter for this measurement
Protection circuit
Disconnect the load resistance from the output terminal. Short-circuit 2 jumper cables within the “DC-C” marked frame of the PS circuit board and check that the power is shut down within 2 seconds. After checking, make short-circuited jumper cables off. Turn off the power and turn it on again 3 seconds later to check that the unit can be restarted normally.
Output level
Input a 1 kHz, -10 dBu signal and check that the output voltage at pins 14 and 15 of JK304 is 4.8 ± 1.0 dBu.
Mute and protection status
Input a 1 kHz, -10 dBu signal.
Check that the DC voltage at pins 10 and 11 of JK304 is +2 ± 0.5V .
Turn on SW1 and check that the DC voltage at pin 11 of JK304 is 0.5 V or less and the voltage level at the output terminal of the A channel is -30 dBu or lower.
Turn on SW2 and check that the DC voltage at pin 10 of JK304 is 0.5 V or less and the voltage level at the output terminal of the B channels is -30 dBu or lower.
Factory settings
Attenuator : MIN (both channels)
MODE switch : STEREO
GAIN switch : 32 dB
HPF switch : OFF (both channels)
CIRCUIT DIAGRAM 
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