Onkyo TXSR-502 Sevice Bulletin
SERVICE BULLETIN
2004/04/21
NO:04003
MODELS : TX-SR502/502E/8250/HT-R520
SUBJECT : The countermeasure against IC oscillation.
Symptom:
TX-SR502's output sometimes has a hum with signals after power on within
few minutes.
When selector or DSP mode is switched to another at this moment, the protect
program starts.
Cause:
Oscillatation of IC regulator.
Procedure for service:
To exchange an electrolytic capacitor with that of 330uF for C6412 in NADG-
8230.
Circuit No. Before
change
Parts No. Description Parts No. Description
C6412 394741007 ELECT C
CE04W16V10M
Marking: No change
Application:
TX-SR502(B) MDD, MDC
HT-R520(B) MDD, MDC #1HT-R520(S) MDD, MDC #1-
After change
394743317 ELECT C
CE04W16V330M
SERVICE BULLETIN No.04003
The countermeasure against IC oscillation.
TOP VIEW
Preamplifier PC board
TX-SR502
1
disconnect
2
C6412
Front
Q6406
Q6406
OUT
heat sink
remove
heat sink
P7502
IN
NADG-8230
heat sink
6
fix with bond
7
P7502
connect
P7502
3
side
Electrolytic Capacitor
330uF 16V
394743317
cut
4
bend
side
TOP VIEW
hook
OUT
GND
heat sink
IN
5
solder
solder
8
Visual Check
1. Check if the capacitor is properly connected to the
IC considering polarity.
2. Check if soldering was done by using just enough
quantity of solder and heat and there remains enough
clearance between the capacitor and the other
terminals or heat sink nearby.
3. Check if just enough bond is used to fix the capacitor
and no bond is left around socket.
4. Check if FFC of P7502B is inserted in the socket in the
right direction from the right angle.
9
Operation Check
Check if sound outputs properly when digital sound signal
is input.
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