Note In Before Starting - Aiwa NSX-MT960 Service Manual

NOTE ON BEFORE STARTING REPAIR
1. Forced discharge ofelectrolytic capacitor ofpower supply block
When repair is going to be attempted in the set that uses relay circuit in the power supply block, electric potential is kept charged
across theelectrolytic capacitors (CIOl, 102) even though ACpower cord isre~oved. Ifrepair isattempted inthiscondition, the
secondary defect can occur.
In order to prevent the secondary trouble, perform the following measures before starting repair work.
Discharge procedure
I
II
Remove the AC power cord.
Connect a discharging resistor at an end of lead wire that
has clips at both ends. Connect the other end of the lead
wire to metal chassis.
Contact the other end of the discharging resistor to the
positive (+) side (+VH) of C 101. (For two seconds)
Contact the same end of the discharging resistor as step
@to the negative (-) side (-VH) of C102 in the same
way. (For two seconds)
Check that voltage across C101 and C 102 has decreased
I II MAIN C.B
1 V or less using a multimeter or an oscilloscope.
[
6
6
Select a discharging resistor referring to the following table.
Fig-1
Charging voltage (V)
Discharging
(Clol, 102)
Rated power (W) Parts number
resistor (Q)
25-48 100 3 87-AOO-247-090
49-140 220 5 87-AOO-232-090
Note:
The reference numbers (C101, C102) of the electrolytic capacitors can change depending on the models. Be sure to check the
reference numbers of the charging capacitors on schematic diagram before starting the discharging work.
2. Check items before exchanging the MICROCOMPUTER
Be sure to check the following items before exchanging the MICROCOMPUTER. Exchange the MICROCOMPUTER after
confirming that the MICROCOMPUTER is surely defective.
2-1. Regarding the HOLD terminal of the MICROCOMPUTER
When the HOLD terminal (INPUT) of the MICROCOMPUTER is "H, the MICROCOMPUTER is judged to be operating
correctly. When this terminal is "L", the main power cannot be turned on. Therefore, be sure to check the terminal voltage of
the HOLD terminal before exchange.
When the MICROCOMPUTER is not defective, the HOLD terminal can also go "L" when the POWER AMPLIFIER has any
abnormalities that triggers the abnormality detection circuit on the MAIN C. B. that sets the HOLD terminal to "L".
Good or no good judgement of the MICROCOMPUTER
@
Turn on the AC main power.
@ Confirm that the main power is turned on and the HOLD terminal of the MICROCOMPUTER keeps the "H' level or
not.
@ When the HOLD terminal is "L" level, the abnormality detection circuit is judged to be working correctly and the
MICROCOMPUTER is judged to be good.
— .—. —.
(
r
-— .—. — .—. _ ._
FRONT C.B ; MAIN C.B
I i
In some models, it is PIN @.
Pi-Azl '91 C CXJ602
MICROCOMPUTER
J_
o —
@
OVER LOAD DET POWER AMP
POWER AMP
POWER SUPPLY
PIN number is different
depending upon microprocessor.
—.— .— - —. .— - —.— .—. —.— . .
Fig-2-1
4