Basic Troubleshooting - JBL GTO 75.4 Service Manual

INSTALLATION AND SETUP
Figure 13. Installing neon tubes in a JBL GTO amplifier.
TROUBLESHOOTING
SYMPTOM LIKELY CAUSE
No audio No voltage at BATT+
(POWER LED or REM terminals,
is off) or bad or no ground
connection
No audio DC voltage on
(PROTECT LED amplifier output
flashes every
4 seconds)
No audio Amplifier is
(PROTECT overheated
LED is on)
No audio Voltage less than 9V on
(PROTECT BATT+ connection
and POWER
LEDs flash)
SOLUTION SYMPTOM
Check voltages at No audio
amplifier terminals (PROTECT
with VOM LED is on)
Amplifier may need Distorted audio
service; see enclosed
warranty card for
service information
Make sure amplifier Distorted audio
cooling is not blocked and PROTECT
at mounting location; LED flashes
verify speaker system
impedance is within
Music lacks
specified limits (see
"punch"
"Specifications" on
the next page)
Check vehicle
charging system for
defective voltage
regulator
7
To Neon
Power
Supply
To Neon
Power
Supply
LIKELY CAUSE
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
GTO 75.4/75.4II
SOLUTION
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