Repair manual

8
b) Leave it switched off with the power cord disconnected for 24
hrs (leave the power cord in at first for 10 mins is this
enough?. This should allow the CRT to discharge)
c) Reset the PMU. In the slot-loaders this can be reached from the
memory access panel. With the iMac on its front and the panel
open, the PMU is about an inch SW of the LH edge of the lower
memory slot. It is about 7mm square and 3mm thick. The reset
button on the top of the PMU is about 3 mm diameter. With the
power cord removed, press it gently but firmly for about _
second. Be careful not to touch any other circuitry. If that
doesn’t help, try doing it with the power cord in place. If the
latter does help, the battery is probably flat.
Intermediate
d) Pull power cable, remove all memory and the Airport card if
present, remove battery from logic board. Leave 24 hrs. In this
order, replace battery with a new one (or confirm good – 3.3 to
3.7 volts), leave 10 secs, reset PMU, replace memory (one card
only, in different position if possible), plug in power, press
power button and startup with original install CD by holding
the “c” key. For slot loaders you need to take the bottom off
the iMac and remove the shielding in order to get inside. For
tray loaders see here. ...also info at Djon's site.
Advanced – potentially dangerous – only if all else fails
(These suggestions may do more harm than good)
e) (This applies to slot loaders only) We need to fool the PMU into
running the full startup sequence even if it previously thought
the PAV board was fried. One method is to unplug the video
connector that connects the video card through to the
motherboard. With the iMac sitting on its screen and its top off,
go for the large metal connector held in by 2 screws that is
right of centre and towards the top of the PAV board. It’s easy
to spot as it is at an angle. Taking the top off the iMac exposes
the high voltage CRT and exposes you to the risk of severe
electric shock. Be very careful and don’t go in there unless you
know what you are doing. Make sure you remove the power
cable first.
Sometimes it seems to be enough to unplug and replug the
connector. In my case it was important to leave everything for
some time; presumably this allows the charge to dissipate. It
might be necessary to leave the iMac turned off but plugged in
to allow the CRT to discharge. It might then be necessary to
leave it off and unplugged to allow the charge on the down
convertor board to dissipate. Having disconnected the video
cable I left it for 10 – 15 mins. I then put the power back in
and touched the power switch a couple of times (no response).
Mac Batteries in the USA
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