Yamaha T3n Service Manual page 37

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3-2. Inspection and adjustment
3-2-1. Fan, POWER/PROTECTION/MUTE LED
Turn on the POWER switch and check the PROTECTION LED and MUTE LED light in red color and the POWER LED lights
in green color.
Also check the fans rotate in low speed.
3-2-2. Power ON muting time
Check at 9 ± 3 seconds after turning on the POWER switch, the muting function is cancelled and the PROTECTION LED and
MUTE LED turn off.
3-2-3. Idling current
Ground the input terminal and adjust VR201 (A ch) and VR202 (B ch) so that the DC voltage between No.1 and No.2 terminal
of CN204 (A ch) and CN203 (B ch) is Vb = 0.1 ± 0.05 mV.
Also, after all inspections, check the Vb value again and adjust so that Vb = 0.1 ± 0.05 mV is obtained.
3-2-4. Output terminal DC voltage
Ground the input terminal and measure the DC voltage (Vdc) of the output terminal.
Check the measured value is Vdc = 0 ± 50 mV.
3-2-5. Efficiency
1) Ground the input terminal via 600 Ω resistance, measure the primary power consumption.
Check the measured value is within the range specified in the table below.
2) Input 1 kHz sine wave to the input terminal and measure the primary power consumption when the output voltage is 28.2
dBu.
Check the measured value is within the range specified in the table below.
3-2-6. Gain
GAIN 32 dB:
Input 1 kHz, -4.0 dBu sine wave to the input terminal and check the output voltage is +28.15 ± 0.5 dBu.
This check should be performed in the PARALLEL mode, too.
GAIN 26 dB:
Change the GAIN switch at 26 dB position.
Input 1 kHz, -4.0 dBu sine wave to the input terminal and check the output voltage is +22.15 ± 0.5 dBu.
After the check, change the GAIN switch at 32 dB position.
3-2-7. Frequency response
Input 20 Hz, 1 kHz, 20 kHz, -4.0 dBu sine wave to the input terminal and measure the output voltage at each time, and then
check the measured voltage at 20 Hz and 1 kHz is within 0.0 +0.0/-0.5 dB as compared with the output voltage at 1 kHz.
3-2-8. Current detecting circuit adjustment
T5n/T4n:
1) Input 1 kHz sine wave to A channel input terminal, adjust the VR601 so that 0.188 ± 0.005 Vrms is obtained between No.1
and No.2 terminal of CN611 when output voltage is 40 Vrms.
2) Input 1 kHz sine wave to B channel input terminal, adjust the VR602 so that 0.188 ± 0.005 Vrms is obtained between No.3
and No.4 terminal of CN611 when output voltage is 40 Vrms.
Note:
• Input the signal to the input terminal of one channel to be adjusted only.
59 ± 10 W
T5n
57 ± 10 W
T4n
52 ± 10 W
T3n
290 ± 30 W
T5n
290 ± 30 W
T4n
290 ± 30 W
T3n
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T5n/T4n/T3n
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