Troubleshooting - JBL PX300.4 Service Manual

Power Amplifier

TROUBLESHOOTING

SYMPTOM
No audio
(POWER LED
is off)
No audio
(PROTECT LED
flashes every
4 sec.)
No audio
(PROTECT
LED is on)
No audio
(PROTECT
and POWER
LEDs flash)
I-E/OPT LED
is on all times
(not flashing)
No audio
(PROTECT
LED is on)
Distorted audio
Distorted audio
and PROTECT
LED flashes
Music lacks
"punch"
LIKELY CAUSE
No voltage at BATT+
or REM terminals,
or bad or no ground
connection
DC voltage on
amplifier output
Amplifier is
overheated
Voltage less than 9V on
BATT+ connection
Amplifier is being
overdriven
Voltage more than 16V
or less than 8.5V on
BATT+ connection
regulator
Input sensitivity is
not set properly, or
amplifier or source
unit is defective
Short circuit in
speaker or wire
Speakers are not
connected properly
6
SOLUTION
Check voltages at
amplifier terminals
with VOM
Amplifier may need
service; see enclosed
warranty card for
service information
Make sure amplifier
cooling is not blocked
at mounting location;
verify speaker-system
impedance is within
specified limits (see
"Specifications" on the
next page)
Check vehicle
charging system for
defective voltage
regulator
Check INPUT
LEVEL setting;
see previous page
Check vehicle
charging system for
defective voltage
Check INPUT
LEVEL setting; or
check speaker wires
for shorts or grounds
Remove speaker leads
one at a time to locate
shorted speaker or
wire, then repair
Check speaker
connections for
proper polarity
PX300.4