JBL E 250P (serv.man15) Service Manual ▷ View online
E250P
Testing Procedure
A. Power Amp Section
Resistance
Check
Resistance from S+ (SPK O/P) to GND should be >1M
Ω
(NO LOAD)
Resistance from V+ (C6 P+) to V- (C8 P-) gradually Fully CHARGED should read >10k
Ω
Resistance from V+ (C6 P+) to S+ (SPK O/P) should read >1M
Ω
Resistance from V- (C8 P-) to S+ (SPK O/P) should read >1M
Ω
2. Power Up LED RED
With a 5mV signal to Low level input, LED should change to GREEN
-Voltage measurements (DVM)
OP AMP
LED
P-U4(1)
P-U4(7)
RED
0Vrms
11.84VDC
GREEN
7.13Vrms
-12.93VDC
3. D.C. Operation
-Voltage measurements (DVM) on CLASS D POWER AMP
Between
V+
Q4(E)
Q1(C)
Q10(C)
U7(1)
U7(2)
U7(4)
U7(6)
U7(7)
U7(8)
And This
Point
GND
V-
GND
GND
GND
GND
GND
GND
GND
GND
Get this
Reading
71.7V
0V
-71.7V
0V
-71.7V
-71.5V
-71.2V
0V
0V
4.65V
4. Check Switching Frequency
•
Oscilloscope - USE THE PROBE TIP TO U6(7) TO GND
•
Reading 100kHz +/-10%,24Vp-p
B. Pre Amp Section
Line Level Input Sensitivity
-Set up
Turn level, X’OVER FREQ POT Fully CW and LFE switch off
Generator Set at 200mV@50Hz
Signal to Line level input
E250P
Testing Procedure
- Voltage measurements
OP AMP
U2(1)
U2(14)
U2(8)
U3(7)
U3(1)
U3(14)
U3(8)
U5(7)
U5(1)
SPEAKER
O/P
306.9mV
461mV
460mV
658mV
628mV
598mV
2.326V
2.02V
3.57V
23.33V
2. High Level Input Sensitivity
-Set up
Turn level, X’OVER FREQ POT Fully CW and LFE switch off
Set Generator at 1.3V@50Hz
Signal to High level input
-Voltage measurements 15.3V at speaker output
3. Low-Pass
-Set up
Set Generator at 200 mV@100Hz
Signal to
Line
level input
Measure voltage at S+ speaker output
-Voltage measurement
X’OVER FREQ. Setting
Output
CW
14.03V
CCW
4.8V
4. LFE
-Set up
Set Generator at 200mV@200Hz
Signal to
Line
level input
Measure voltage at S+ speaker output
LFE switch Setting
Output
Normal
6V
LFE
18.32V
See flow chart next page for diagnostics.
E250P
Testing Procedure
POWER MODULE TESTING 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+.
(A 10mV signal may need from the input to trigger the Switch turn on)
no
no
yes
yes
no
no
yes
yes
no
no
yes
yes
no
no
yes
yes
START
Check +/-15V-MOD
+/-15V voltage at
U 6(8),U6(4)
Discharge C37,
Check fuse
transformer, L4,
rectifier, C6 and C8
Use scope to check
switching
frequency U6(7)
100KHz
+/-10% , ~24Vp-p
Check Q4(E)
TO V-
= 0V D.C.
Power up with no
signal input
LED RED
OK
OK
OK
OK
OK
OK
OK
OK
Check
MUTE(+8V) and
Q24,Q25,Q26
Use scope to
check O/P U7(6)
and GND
143Vp-p square
wave shown
Check
L2,L3,C71,C72,
C73,C74
I/P:10mv/50HZ
Check +15V/SW
Q4(E) TO V-
15V
Replace
Q18,Q22
CLASS D AMP OK
END
Check
U7,Q16,Q17,
Q20,Q21,R87,
D26,D35,C64
Check
FB1,FB2,C45,
C50,C60,C63,
R81,R82
Check
U7(1) = -58.3V
Check
MUTE
(-12.9V),
And
Q24,Q25,Q26
Resistance check
(no load)
between V+ V-,
V+ O/P,V- O/P
and O/P to GND
is > 10K
Block Diagram
Rin
Lin
Rout
Lout
Line Level
Input
Input
DIF. AMP
SUMMI NG AMP
VOLUME CTRL
PHASE CTRL
SWITCH
SWITCH
AMP STAGE
12dB/Octave
HPF
LPF
12dB/Octave
12dB/Octave
LPF
Variable
SUMMI NG AMP
LIMITER /
LPF
LPF
MUTE
DC OFFSET
PROTECTION
PROTECTION
THERMAL
PROTECTION
PROTECTION
CURRENT
PROTECTION
PROTECTION
LINEAR
POWER SUPPLY
* FUSE
MUTE
SIGNAL SENSE
ATO
SIGNAL SENEING
EXTERNAL LED INDICATORS
CONTROLLED
REGULATOR
REGULATOR
CLASS D
AMPLIFIER
AMPLIFIER
+15V SW
MUTE
OUTPUT-RELAY
5.6 OHMS
LFE
NORMAL
NOTE :
120 VAC T2A-250V
230 VAC T1.25A-250V
120 VAC T2A-250V
230 VAC T1.25A-250V
SPEAKER LEVEL
INPUT
INPUT
F
1
E
D
3
2
C
B
A
1
2
3
4
7
6
8
F
E
D
5
RevNo
Revision note
6
7
C
B
Checked
8
Date
Signature
A
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