JBL service manual Detailed Troubleshooting Contd, E250P/P12SW subwoofers, Flow Chart

E250P/P12SW subwoofers

DETAILED TROUBLESHOOTING (CONT'D)

FLOW CHART

CAUTION : SPEAKER OUTPUT IS FLOATING AND IS NOT PROTECTED AGAINST A SHORT TO GROUND. ALL TEST INSTRUMENTS CONNECTED TO THE OUTPUT MUST

BE FLOATING. ATTACH THE SCOPE PROBE TIP TO S - and REFERENCE LEAD TO S+.

START

(A 10mV signal may need from the input to trigger the Switch turn on)

Resistance check
(no load)
between V+ V-,		Check +/-15V-MOD
V+ O/P,V- O/P		+/-15V voltage at
and O/P to GND		U 6(8),U6(4)
is > 10K			Check
		no	FB1,FB2,C45,
no	Replace	OK	C50,C60,C63,
			R81,R82
OK	Q18,Q22
		yes
yes
		I/P:10mv/50HZ
Power up with no		Check +15V/SW
		Q4(E) TO V-
signal input
		15V
LED RED
	Discharge C37,	no	Check
no		OK
	Check fuse		MUTE(-12.9V),
OK
	transformer, L4,	yes	And
	rectifier, C6 and C8		Q24,Q25,Q26
yes
		Check
Check Q4(E)		U7(1) = -58.3V
TO V-
= 0V D.C.
		no	Check
no	Check	OK	U7,Q16,Q17,
			Q20,Q21,R87,
OK	MUTE(+8V) and
		yes	D26,D35,C64
	Q24,Q25,Q26
yes
		Use scope to
Use scope to check		check O/P U7(6)
		and GND
switching
		143Vp-p square
frequency U6(7)
		wave shown
100KHz
+/-10% , ~24Vp-p
		no
		OK
no
OK		yes
yes		Check
		L2,L3,C71,C72,
CLASS D AMP OK		C73,C74
END
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