iMac G4 - 800Mhz - 17" - will NOT turn on

The standard battery most Mac desktop computers use
is a lithium cell by the name of: 1/2AA 3.6v. Lithium.
They can be bought retail for about $10. or sometime less.

The power management reset button is located under
the metal bottom coverplate, hidden under the plastic
protective layer. You should not have to remove the
plastic to access or press the button. See this page:

• Resetting the iMac (flat panel G4) Power Management Unit (PMU)
http://support.apple.com/kb/HT1712?viewlocale=en_US

Replacing the battery, is another story; and the attention
to detail is very important. You have to go into the iMac G4
at the same level of difficulty to replace this battery, as you
would if you were going to replace or upgrade a hard drive.

{This would include the need to re-apply thermal paste and
also torque some screws to factory specs, as part of the job.}

• iMac G4 Take-apart for Drive and RAM upgrades:
http://www.xlr8yourmac.com/systems/imacg4/imacg4takeapart.html

• mr. totes iMac G4 takeapart with images:
http://www.mrtotes.co.uk/page1/page1.html

Hopefully these page links and information may be of help in this matter.
Good luck & happy computing! 🙂

Garry,

as soon as I put the plug into the wall I heard a pop noise even before I turned the iMac on

I always hear this pop or often even a spark when I plug in a computer power supply. These are switch mode supplies and it's normal for them to spark when you first plug them in. I actually take that as a sign of a healthy power supply. If I don't see or hear that I'm immediately suspicious of the power supply.
If you look at this circuit:
http://www.smps.us/SMPS_schematic.gif
you see that section that they call "housekeeping circuit". Well in the iMac there's a similar circuit but it's referred to as the "trickle voltage". That's the voltage that's always present in a modern computer that activates the "soft start" circuit.
So as to the battery. I'm looking at the service manual "updated 2003 June 3" for the 17" 800 MHz. Under the section "No Power":
"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 “Main” (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, verify that all the cables are
securely connected and test the unit again. Pay special attention to the video cable.
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."
A dead battery has been known to cause the no start scenario. Probably since the PMU uses that battery to power itself.
Email me if you need more info.
Richard

Message was edited by: spudnuty

Message was edited by: spudnuty

Certainly has some of the symptoms of needing a technician to
inspect and do the troubleshooting; however be sure to not put
a whole lot into such a computer without checking first into the
actual costs to get another or a newer model in good health.

If this route is taken, it is possible to retrieve your data from the
old iMac's hard drive by putting that hard disk drive in an external
hard drive enclosure; the next steps would vary depending on
what the data is, wanted to be saved, and what computer is may
be accessed through to recover or use it.

There is a chance the iMac G4 800 may be salvageable, though.
The power supply and some other items are replaceable parts.

Good luck & happy computing! 🙂

The matter of getting a replacement part for an iMac G4 with 17" display
has to include the issue of there being more than one 17" model; and
the differences are, the newer model is USB2.0 and has a faster CPU.
The bus speed is different, and likely the power supply is, too.

If you can compare the part number for the 800MHz 17" iMac G4 listed
in the expanded view (and perhaps also shown beneath image, with link)
to the one you have an ebay link to; if these really are the same, then
and after confirming the actual reality IF they are compatible, it may work.

Though I am not suggesting the providing link is anything other than a
place to check and compare specification information, I also recommend
to double or triple check to verify actual compatibility of parts by Apple
Part numbers before ordering or investing in the prospects of a repair.

An Apple Part number (for your iMac G4 800MHz with 17" LCD) is: 922-5302; but
viewed in the expanded-view at the linked web page; however there is potential
conflict of information when noting the replacement part number, where I see it
is listed as: "17" iMac G4, Power Supply, 661-3185 Apple original part."

• in reference to Power Supply: 800MHz iMac G4 17" replacement part specs
http://www.mac-pro.com/Mac-Pro-Online-Store/G4-iMac-17-Parts-Flat-Panel-800Mhz

While some later replacement parts may be compatible with more than
one iMac G4 model, the gap between the older USB1.1 iMac G4 and
later USB2.0 iMac G4 models would indicate the Power Supply Unit
said to be for an iMac which is running PC2700/DDR333 RAM would
not likely be the correct one for an older one iMac G4 configuration with
different specifications and not of the same build series.

(So, this is an area worth researching for more detailed information..
one searched source suggests the one part number listed replaced
the older number. The manufacturer of one replacement or OEM part
was: Manufacturers ID: Samsung PSCF151101A 614-0187.)

If you had, say, an iMac G4 USB2.0 1.25GHz 17" model and wanted to
know if the power supply from an iMac G4 1.25GHz 20" model may work;
then there is a close chance that a replacement part may work in both.

But the older iMac G4 800MHz 17" USB1.1 model, is more different than
the later part number listed in the Ebay page. It could be way too new.

So, further investigation into these kinds of matters is suggested.
Good luck & happy computing! 🙂