Apple imac 20 inch early 2008 User Manual
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iMac (20-inch Early 2008) Troubleshooting — General Information 2 31 Logic Board Sensor Locations, Back Side This is a photo of the back side of the iMac (20-inch Early 2008) logic board showing the GPU and CPU sensor connector locations. Cleaning Tools for the LCD and Glass The following tools are necessary when servicing this product. Order a cleaning kit, (076-1277), which contains all the items listed, or purchase the tools individually.Suction cups, one pair (922-8252) • Sticky silicone roller (6-inch) to clean the glass panel, Qty. of one (922-8261)• Sticky sheets to clean the silicone roller, Qty of 2 pads (922-8262)• Polishing cloths, clean, anti-static, micro fiber “terry” style cloth, Qty. 5 cloths, (922-8263)• Gloves, lint-free, anti-static, Qty. of two (922-8253)• Microfoam bag to store the glass panel, Qty. of one (5 bags) 922-8259)• ESD bag for LCD display storage, Qty. of one (5 bags) (922-8258)• ESD bag for LCD display storage (922-8258)•
iMac (20-inch Early 2008) Troubleshooting — General Information 232 LensPen Cleaning Tool LENSPEN products are simple to use and are effective at removing smudges and fingerprints on the inside/outside of the glass panel. The two LENSPEN products that have been tested on the iMac are shown below, the VidiMax and the LapTop-Pro. Refer to www.lenspen.com for more information.
iMac (20-inch Early 2008) Troubleshooting — General Information 233 Ionizing Air Gun The ionizing air gun is an optional tool you may want to consider when cleaning iMac glass panels. The ionizing gun performs electrostatic elimination and dust removal instantly with ion balanced air. Various sources can be found on Google.
iMac (20-inch Early 2008) — Symptom Charts 234 Symptom Charts When to Use the Symptom Charts Before turning to the symptom charts, you should have completed the following steps on the Apple General Troubleshooting Flowchart: Gather information 1. Verify the problem2. Try quick fixes3. You consult the symptom charts as part of the Research troubleshooting step (and sometimes as part of the Try Quick Fixes step). How to Use the Symptom Charts The Symptom Charts included in this chapter will help you diagnose specific symptoms related to the product. Diagnostic steps are listed on the charts in the order of most likely solution: try the steps in the order presented. Verify whether or not the product continues to exhibit the symptom. If the symptom persists, try the next step. Important Note: If a step instructs you to replace a module, and replacing that module does not resolve the symptom, reinstall the original module before you proceed to the next step. Diagnostics The following diagnostic tools are available for this product: Apple Hardware Test • Distributed to customers worldwide who purchase a new Apple computer - Apple Service Diagnostic: • Sent to Apple Authorized Service Providers as part of the Macintosh Family Diagnostics -subscription mailing See Knowledge Base document 11212 5, “Service Diagnostic Matrix”, to download the appropriate disc images. The Service Diagnostics Matrix is a guide to service diagnostic software from Apple, including the Apple Service Diagnostic, MacTest Pro, display service and adjustment utilities, and Apple Hardware Test for MacBook, MacBook Pro, Mac mini, iMac, eMac, PowerBook, and Power Mac products.
iMac (20-inch Early 2008) — Symptom Charts 235 Apple Hardware Test (AHT) Error Codes The error codes listed below are the most likely codes that will be generated if a sensor cable is disconnected, dislodged, or if the system has a faulty cable or sensor. Clicking on the link in the chart will show you where the sensor and/or cable is located. AHT ErrorSuspected partSuggested ActionNotes 4SNS/1/40000000:Tp0P Power supply sensor pin/power supply Verify that the single pin connector on the top edge of the power supply is present and securely plugged in. If connector is damaged replace the DC Power Supply cable.If this sensor signal wire is disconnected or faulty the CPU fan will run at full speed. 4SNS/1/40000000:T00P ODD temperature sensor on ODD damaged or cable disconnected from MLB Verify that the sensor cable is securely connected to the MLB and the sensor is properly attached to the ODD mechanism. Replace the sensor if it is damaged.If this sensor is disconnected from the MLB or it is faulty the ODD fan will run at full speed. 4SNS/1/40000000:TA0P Ambient temperature sensor damaged or cable disconnected from MLB Verify that the sensor cable is securely connected to the MLB and the sensor attached to the left speaker housing properly attached. Replace the sensor if it is damaged. 4SNS/1/40000000:TL0P LCD temperature sensor on LCD damaged or cable disconnected from MLB Verify that the LCD sensor cable is securely connected to the MLB and the sensor is attached to the LCD. Replace the sensor if it is damaged.If the sensor is disconnected the CPU fan will run at full speed. 4SNS/1/40000000:TG0H GPU temperature sensor (located on back side of MLB/video card) is disconnected or faulty. Verify that the two pin sensor cable is securely connected to the MLB. The connector is located on the back side of the MLB and requires removal of the MLB to access it. If it continues to fail the diagnostic replace the video card.If the sensor is disconnected the CPU fan will run at full speed.
iMac (20-inch Early 2008) — Symptom Charts 236 AHT ErrorSuspected partSuggested ActionNotes 4SNS/1/40000000:TC0H CPU temperature sensor (located on back side of MLB) is disconnected or faulty. Verify that the two pin sensor cable is securely connected to the MLB. The connector is located on the back side of the MLB and requires removal of the MLB to access it. If it continues to fail the diagnostic replace the logic board.If the sensor is disconnected the CPU fan will run at full speed. 4MOT/1/40000002:ODD Optical drive blower/ fan Verify that the ODD blower/fan cable is securely connected to the MLB and that there are no obstructions that would prevent the blower/fan from rotating. Replace the optical blower/fan if the error continues. 4MOT/1/40000002:HDD Hard drive blower/fan Verify that the hard drive blower/fan cable is securely connected to the MLB and that there are no obstructions that would prevent the blower/fan from rotating. Replace the hard drive blower/fan if the error continues. 4MOT/1/40000002:CPU CPU blower/fan Verify that the CPU blower/fan cable is securely connected to the MLB and that there are no obstructions that would prevent the blower/fan from rotating. Replace the CPU blower/fan if the error continues.
iMac (20-inch Early 2008) — Symptom Charts 237 Power Issues System Intermittently Shuts Down or Restarts Unexpectedly Check the connection of the power cord on both ends. Verify that the power cord is securely 1. plugged into a good AC outlet and that the cable is fully inserted into the back of the computer. Did re-seating the power cord resolve the problem? Yes: The power cord may have a loose fit or it wasn’t fully inserted into the receptacle on the back of the iMac. Replace the AC power cord and test again. If the customer continues to report shut down or restart issues resume with step 2 of this troubleshooting symptom. No : Go on to the step 2. If the iMac has been previously serviced, verify that all cables and connectors are firmly seated. Pay special attention to the DC power supply cable where it connects to the DC power supply and the logic board (shown below). Note: The latest version of the DC Power Supply/SATA/Inverter cable (922-8188) be identified by the presence of a part number label on the end of the connector that plugs into the main logic board. With earlier versions of the cable, the part number label is hidden by the chassis and cannot be easily viewed when it is installed in an iMac.
iMac (20-inch Early 2008) — Symptom Charts 238 Does the computer continue to unexpectedly shut down or restart? 2. Yes: Replace the DC, Power Supply/SATA/Inverter cable (922-8188) shown below. Note: The latest version of the DC Power Supply/SATA/Inverter cable be identified by the presence of a part number label on the end of the connector that plugs into the main logic board. With earlier versions of the cable, the part number label is located on the cable, but the label is hidden by the chassis, and cannot be easily viewed when it is installed in an iMac. Carefully follow the take-apart instructions to ensure that the replacement cable is correctly routed and the sensors and fans are properly connected. Test thoroughly. Run Apple Hardware Test. Refer to the Apple Hardware Test Error Code Table if you incur an error. No : Return the computer to the customer. If the customer continues to report shut down or restart issues during the next month resume with step 3 of the troubleshooting. Replace the power supply. 3. Replace the main logic board.4.
iMac (20-inch Early 2008) — Symptom Charts 239 No Power The computer will not turn on. The display remains black and there are no sounds from the fans or drives. 1. Verify the power outlet is good. Plug a different device into the socket to ensure there is power, or plug the iMac into another outlet. Does the iMac power on now? Ye s: Resolved. Bad outlet. No : Go on to the next step. 2. Check the power cord. Use a known good power cord. Does the iMac power on now? Ye s: Your power cord has failed. Replace the AC power cord. No : Go on to the next step. 3. Check the connection of the power cord on both ends. Verify that the power cord is securely plugged into both the AC outlet and back of the computer. Does the iMac power on now? Ye s: You may have a loose fit to your power cord. Replace the AC power cord and test. No : Go on to the next step. 4. Follow instructions in the General Information chapter to reset the SMC. Does the iMac power on now? Ye s: Issue resolved. No : Go on to the next step. 5. Remove and reinstall the SO-DIMM memor y modules, located in the bottom of the computer. Does the iMac power on now? Ye s: Issue resolved. No : Go on to the next step. 6. Remove the memory access door and front bezel to gain access to the four diagnostic LEDs. See “Diagnostic LEDs” in the General Information chapter for complete instructions on this procedure. 7. Plug the power cord into the iMac and the power cord into the AC outlet. Check to see if LED #1 is On or Off. LED #1 is On: This indicates that the power supply is getting good power from the AC outlet. Go on to the next step. LED #1 is Off: This indicates that the computer is not detecting AC power. If both the AC outlet and the power cord are good, replace the AC/DC power supply. If the issue persists, replace the AC line filter. 8. Press the power button. Check to see if LED # 2 comes On, comes on momentarily, or stays Off.
iMac (20-inch Early 2008) — Symptom Charts 240 LED # 2 is On: The Power Supply is functioning. Go on to the next step. LED # 2 comes on momentarily or stays Off: Replace the Power Supply. 9. At this point in the Power On process, you should hear a boot chime and see that LED #1 and #2 are On. Do you hear a boot chime? Ye s: The power systems of the computer are working correctly. See “Troubleshooting No Video” in this chapter. No : The logic board is not passing the Power-On Self Test (POST ). Replace the SDRAM with known-good memory and test. If the issue persists with known-good SDRAM, replace the logic board. Appears to be a “no power” situation, but the computer turns on, the display remains black and the fans are running. Make sure all software updates have been applied to the computer. 1. Check that all the temperature sensors are connected.2. Run Apple Hardware Test to verify all sensors and cables are connected and functioning. 3. Refer to the Apple Hardware Test Error Code Table for additional information. Video No Video, No Boot Chime The computer will turn on, but there is no boot chime and no video on the display. The faint sound of the fans, hard drive, and optical drive may also be heard. 1. Make sure all software updates have been applied to the computer. 2 Follow instructions in the “General Information” chapter to reset the SMC. Does the computer display video after successfully resetting the SMC? Ye s: Problem solved. No : Continue to next step. 3. Verify that only supported SDRAM memory has been installed and that it has been installed correctly. Unsupported and/or defective memory can prevent the computer from booting. It may be necessary to install known good memory for testing purposes and replace any unsupported or defective SO-DIMM’s identified during this process. Does the computer display video after verifying and/or replacing the memory with known good memory? Ye s: Problem solved. Verify full system functionality before return the system to the customer. No : Replace the logic board.