Awesome manual. Complete diagrams of all board assemblies as well as how to get to each part of the t.v. down to the individual screws and their locations. Get it.
This is exactly the service manual I needed.
Complete with all schematics, partslists, PCB layouts and alignment instructions.
This manual covers both the T-4970 en T-488F Onkyo tuner.
Text excerpt from page 7 (click to view)
Power Amplifier TROUBLESHOOTING
SYMPTOM No audio (POWER LED is off) No audio (PROTECT LED flashes every 4 sec.) 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 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
Amplifier is overheated
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
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
Distorted audio and PROTECT LED flashes Music lacks �punch�