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A-8780
1. Preparations
2) Set up the unit as follows.
(1) No load
(2) No signal
(3) Volume turned all the way down
(4) Speaker switch OFF
(5) Power switch OFF
2. Idling current adjustment
1) Turn the power switch ON and allow the unit to warm up for about 10 minutes.
(1) Adjust R535 (R536) so that the voltage at test point VCT-IID on the NAAF-3915 circuit board is 15mV+SmV.
Note)
Semi-fixed resistors enclosed in parentheses (_ ) are for the right channel.
3. Check of operation of protection circuitry
1) Check of operation of protection relay
(1) Confirm that the relay turns ON approximately 5 seconds after the power switch is turned ON.
(2) The relay should turn OFF approximately 0.5 seconds after the power switch is turned OFF.
2) Check of DC detection and servo circuitry operation
(1) Turn the power on with no load.
(2) After the speaker relay turns ON, apply DC+200mV to the CD input terminals. Confirm that the relay turns OFF.
(3) Confirm that operation is the same as (2) above when an input of DC—200mV is applied.
Note) Under no circumstances connect a load or short the speaker terminals when performing the above tet.
3) Signal input from the circuit illustrated below with no load.
(1) Confirm that the speaker relay does not turn OFF even when a 2 ohm load is connected when a peak value of 35V
p-p is output.
;
(2) Next, confirm that when a 1 ohm load is connected the speaker relay switchse OFF and ON a couple of times
and then stays OFF.
Note) The period before that relay stays OFF should not fast for more than 1 minute.
Relay OFF status can be canceled by switching the power OFF.
Low-frequency
oscillator
Amplifier
SP
Load
OUT
a
Differe-
ntiator
Attenua-
tor
Square wave
The unit's volume
50Hz,
10V p-p
control
may
also
be used.
Oscillo-
scope
3.3 KQ
O.1
uF
3.3 KQ
OUTPUT
Square
wave
input
fron
low-frequency
oscijlator
10 KQ
50 Hz, 10V p-p
Wa
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