Missing barcode label in iMac G4- i need that EEE code!

Question

I need to replace the logic board on my G4 iMac. On the board I can find the part number and an empty box etched with the words 'barcode label'. Is it possible that my logic board has no serial number? Or has a lazy technician in my past tossed it out? How do I find out what part I need? The logic board part number 820-1501-A, the iMac serial number is W8***NHX. I would appreciate any help on this one. Thanks.

Answer 1

Hey John,
It's possible there's a problem with the PMU. Not sure how the PMU works in these iMac G4s. I do see a block diagram for the iMac Flat Panel 700 and 800 but none for the 1 GHz. In that block diagram the PMU inputs to something called the Panges memory controller and I/O device controller. So a lot of things run through this chip including ATA, wireless LAN USB, Firewire , Ethernet....
You might run through these voltage checks from the manual:
"4. Remove keyboard, mouse, and other peripherals such as speakers.
5. Disconnect the power cord, place the computer in the service stand, and remove the user access
plate.
6. Reset PMU. Refer to “Resetting the PMU on the Logic Board” mentioned earlier in this chapter.
7. Using a voltmeter, check the voltage on the battery test point (see graphic below). If the reading is over
3.5 volts, go to the next step. If the reading is under 3.5 volts, replace the battery and test again.
8. Plug the unit in, but do NOT press the power button. Using a voltmeter, check the voltage from the test
point marked “12VSLP” (see graphic above). You should get a reading of approximately 12 volts. If the
reading is 12 volts, go to the next step. If you don’t get a 12 volt reading, go to step 11.
9. Press the power switch on the computer. Using a voltmeter, check the voltage on the test point marked
“12V” (see graphic above). You should get a reading of approximately 12 volts. If the reading is 12
volts, go to the next step. If you do not get a 12 volt reading, replace the main logic board.
10. Using a voltmeter, check the voltage on the test point marked “5V” (see graphic above). You should get
a reading of approximately 5 volts. If the reading is 5 volts, go to the next step. If you do not get a 5 volt reading, replace the main logic board."
Those test points are under the user access panel on the bottom near the PMU button that you've already found. They're in the form of an "L" that faces to the left. Close to the apex is the ground point the tip of the lower leg being the battery test point and the tall upright being:
5 V
12 VSLP
!2 V
from top to bottom.
If you have more questions email me.
Richard