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 105 (click to view)
XR-A550MD
¶ Disc loading is incorrect
Is disc loaded when it is inserted? NO Is Pin 4 of CN1601 set to "L"? YES Does either Pin 23 or 24 of IC1601 change? YES NO NO Check IC1401. NO Check CN1601 and SW1956. YES
Does either Pin 30 or 31 of IC1601 change? YES Check the CN1604.
NO
Check CN1604 and IC1601.
YES Does the system eject when the MD removal button is pressed? YES The disc table retracts after ejection is completed. YES Check CN1601 and SW1956. NO
¶ The system does not playback
The system play back neither reflection discs. NO The system does not playback only high-reflection discs. YES Is Pin 93 of IC1401 set to 1.02V±0.3V in Test mode, with high-reflection disc inserted? NO YES YES NO YES Go to "CHECKING BY TEST MODE". NO The system does not play back only low-reflection discs. YES Is Pin 93 of IC1401 set to 2.06V±0.3V (recording possible), 3.2V±0.3V (recording prohibit) with low-reflection disc inserted?
