JBL GTO75.4II
Service Manual

GTO 75.4/75.4II INSTALLATION AND SETUP

To Neon Power Supply

To Neon Power Supply

Figure 13. Installing neon tubes in a JBL GTO amplifier.

TROUBLESHOOTING
SYMPTOM No audio (POWER LED is off) No audio (PROTECT LED flashes every 4 seconds) No audio (PROTECT LED is on) LIKELY CAUSE No voltage at BATT+ or REM terminals, or bad or no ground connection DC voltage on amplifier output 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 SYMPTOM No audio (PROTECT LED is on) Distorted audio 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 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

Amplifier is overheated

Distorted audio and PROTECT LED flashes Music lacks �punch�

Speakers are not connected properly

No audio (PROTECT and POWER LEDs flash)

Voltage less than 9V on BATT+ connection

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