Yamaha EMX62M, Service Manual

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33
EMX62M
3.8 Stability Check
(1) Connect 10pF~0.47
µ
F capacitor in parallel to the 4
Ω
load resistance and apply rectangule signal of 10kHz/-26dBs.
Then, confirm that overshoot and ringing are as follows.
Overshoot: Vp/Vo 1.8
Ringing: within 5 waves
(2) Connect 10
µ
H~0.47H inductor in series to the 4
Ω
load resistance and apply rectangule signal of 10kHz/-26dBs.
Then, confirm that overshoot and ringing meet the same condition as (1).
(3) Remove the 4
Ω
load resistance and connect only 10pF~0.47
µ
F capacitor as load, and apply rectangule signal of 10kHz/-
26dBs.
Then confirm that the system does not oscillate.
Besides, confirm that overshoot and ringing are as follows.
Overshoot: Vp/Vo 2.5
Ringing: within 7 waves
3.9 Protection Circuit Check
•
Apply 10Hz signal until output level is saturated, and confirm that the protection circuit works and the relay does not open.
•
Apply 1Hz, Vp-p = 6V(8.7dBs) signal, and confirm that the protection circuit starts to work in 2 seconds to cut off the signal.
•
Stop applying the input signal, and confirm that the system automatically resumes in 5 seconds.
3.10 PC LIMITER Circuit and LIMITER Circuit Check
Connect 1
Ω
(
±
5%, 100W) load and apply -20dBs signal into input terminal.
Mesure the output level and confirm that Vp-p 20V and the waveform is not a rectangule.
3.11 LIMITER Indicator Check
Apply 1kHz/-10.8dBs signal, and confirm that LIMITER indicator lights up.
3.12 Efficiency Check
Adjust the input level so that the output level of SPEAKER becomes 10V (22.2dBs).
Then confirm that the primary power is 100
±
20W.
4. Miscellaneous
4.1 Power Supply Voltage Variation
Change the voltage of power supply in the range of
±
10%, and confirm that the system works normally.
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