JBL PowerBass PB10 Service Manual page 28

PB10
PB10 Testing Procedure (Cont.) (Revision 2 Only)
PB10 POWER MODULE TESTING FLOW CHART - REVISION 2 ONLY
CAUTION : SPEAKER OUTPUT IS FLOATING AND IS NOT PROTECTED AGAINST A SHORT
START
Resistance check
(no load)
between V+ V-,
V+ O/P,V- O/P
and O/P to GND
is > 10K
OK
Power up with no
signal input
LED RED
OK
Check Q4(E)
TO V-
= 0V D.C.
OK
Use scope to check
switching
frequency U6(7)
100KHz
+/-10% , ~22Vp-p
OK
CLASS D AMP OK
END
TO GROUND. ALL TEST INSTRUMENTS CONNECTED TO THE OUTPUT MUST
BE FLOATING. ATTACH THE SCOPE PROBE TIP TO S - and REFERENCE
LEAD TO S+.
(A 10mV signal may need from the input to trigger the Switch turn on)
no
Replace
Q18,Q22
yes
Discharge C37,
no
Check fuse
transformer, L4,
rectifier, C6 and C8
yes
no
Check
MUTE(+8V) and
Q24,Q25,Q26
yes
no
yes
Check +/-15V-MOD
+/-15V voltage at
U 6(8),U6(4)
OK
I/P:10mv/50HZ
Check +15V/SW
Q4(E) TO V-
15V
OK
Check
U7(1) = -33V
OK
Use scope to
check O/P U7(6)
and GND
90Vp-p square
wave shown
OK
yes
Check
L2,L3,C71,C72,
C73,C74
28
Check
FB1,FB2,C45,
no
C50,C60,C63,
R81,R82
yes
no
Check
MUTE (-10.7V),
And
yes
Q24,Q25,Q26
no
Check
U7,Q16,Q17,
Q20,Q21,R87,
yes
D26,D35,C64
no