Logic Board Bottom

The PMU (Power Management Unit) is a microcontroller chip that controls all power functions for the computer. The PMU (location shown below) is a computer within a computer. It has memory, software, firmware, I O, two crystals, and a CPU. Its function is to Tell the computer to turn on, turn off, sleep, wake, idle, etc. Manage system resets from various commands. Maintain parameter RAM (PRAM). Manage the real-time clock. Important The PMU is very sensitive and touching the circuitry on the...

Logic Board Battery

Important Apple highly recommends removing the battery when handling the logic board. Make sure to use proper ESD protection when handling modules. The battery on the logic board controls the stored system settings, such as date and time. It is only necessary to test the battery when you can't power on the computer, or the date and time are reset every time the AC power is removed. The battery is also used to power the PMU chip because the PMU chip keeps time and must always be running when the...

Thermal Pad Replacement Instructions

Whenever the logic board is separated from the bottom housing, you must install new thermal pads to three surfaces on the bottom housing. The thermal pads help cool components on the logic board. Failure to apply these pads whenever the logic board is separated from the bottom housing could cause these parts to overheat. Short term separation, where the thermal pads are not handled excessively an exception would be if you are simply testing the logic board and only detach it for a few minutes ,...

Diagnostic Test Points

Imac Flat Panel 1ghz Botton

The iMac has four test points and one ground pad on the bottom of the logic board next to the PMU and AirPort Extreme Card . These test points are accessible under the customer access panel via small cutouts in the plastic shielding see below . These test points provide an easy troubleshooting tool for common problems. To use each test point, put the positive probe of your voltmeter on the test point, and the negative probe on the ground pad.

Procedure

Imac Flat Panel Disassembly

Pull the neck cables white spokes out of their slots and into a bundle. Bundle the neck cables to one side. Supporting the base, remove the two black screws that connect the neck to the Faraday base. _ 2. Carefully feed the neck cables through the hole in the Faraday cage. Important The Faraday cage is very heavy and has sharp edges handle with care. 3. Pull the outer shell with Faraday attached away from the neck.Note There is no need to remove the outer shell from the Faraday unless you...

Display Tilt

Screen tilts to the left or the right even after a manual adjustment. Note It is normal for the screen on an iMac Flat Panel to have a small amount of horizontal play. However, the screen should be able to be adjusted so that it will stay in a level horizontal position. 1. Remove ten screws connecting the back cover to the flat panel LCD display refer to the Take Apart chapter, display topic . 2. Disconnect the panel cables to gain access to the three screws on the metal cable retainer shown in...