JBL LS Series, Service Manual

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LS120P(UL) AMP
Troubleshooting Flow Chart
no
yes
yes
yes no
yes
yes
LED red
LED light Green
yes yes
no
yes yes no
no
yes
yes yes
no
no
yes yes
yes
no
yes
yes
AMP no signal out
DC voltage check ±Vcc
Check +/-15v
LED light Green or red
Check fuse, transformer,
D123.D124 etc
Check Class300W MODUL
Check D130,R263.265etc
Check ,+vbbp&-vbbp
DC voltage
Check Relay K101 etc
Check Q116,Q117,Q118,,D122
Check,Q102,101,U103 etc
Check P104 pin8 signal
Check U105
Pin7 signal
Test J111 signal
Check P102 signal
The Amp ass
y OK, END
Check U101,R233,286 ,
U102, etc
Check R257.R258 etc
Check limiter Circuit C151
Check U106 r204.205.206.207
D112.D113, etc
Change Q108.109.110.111 etc
12
LS120P