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colinm
14th June 2007, 08:23 PM
Hi All,

I have a 400MHz G4 tower (Sawtooth) which is refusing to boot.

It was OK this afternoon - the problem may (or may not) have been caused by me installing more RAM. The RAM came from a friend who had the RAM working OK in his similar G4.

After adding the RAM, on restarting, there was no chime or video, but there was a faint burning smell, so I immediately turned it off.

The G4 will now turn on from the front panel button and from the keyboard button - but there are no chimes and there is no video. I can hear the HD spinning and the CD tray will open and close when I press the front panel button.

I have tried:

removing the PRAM battery
Removing the RAM - and restarting with different RAM.
Starting with no RAM (which should give a "no RAM" chime)

all to no avail.

I'm wondering if the motherboard has been fried, but I haven't heard of RAM (previously tested to be OK) doing this. The RAM modules were seated properly too. The burning smell didn't seem to be coming from near the RAM, but it dissipated before I could localise it.

Any ideas would be much appreciated.

Byrd
14th June 2007, 08:34 PM
Do you know that the RAM you're using is 100% working? Try other RAM slots, disconnect graphics card/any other cards, IDE, everything - just a known working CPU, single stick RAM.

The last thing to try is to press the PMU switch for two seconds? Don't press it anymore after that, otherwise it will kill it.

JB

colinm
14th June 2007, 08:39 PM
Thanks Byrd, will give it a try after the approaching thunderstorm passes.

stewiesno1
14th June 2007, 09:18 PM
By "similar" G4 , which model are you talking about ?
You haven't crimped any cables when you closed the case back up or disturbed any other wiring have you?
Stewie

colinm
14th June 2007, 11:25 PM
Do you know that the RAM you're using is 100% working? Try other RAM slots, disconnect graphics card/any other cards, IDE, everything - just a known working CPU, single stick RAM.

The last thing to try is to press the PMU switch for two seconds? Don't press it anymore after that, otherwise it will kill it.

JB

Thanks Byrd, I tried as you suggested - and even the PMU switch (for only 2 seconds) - no change. Oh well. The RAM was fine bedore whatever happened - and I've tried it with several different RAM modules.

colinm
14th June 2007, 11:26 PM
By "similar" G4 , which model are you talking about ?
You haven't crimped any cables when you closed the case back up or disturbed any other wiring have you?
Stewie

G4 Sawtooth 400MHz.

Thanks fr the suggestion on checking the cables. All seems normal.

yinyang
15th June 2007, 12:49 AM
i vaguely remember being told that no start up chime = logic board in serious trouble, but suggest you speak to a qualified tech first!

hope it isn't too bad....!

Byrd
15th June 2007, 09:05 AM
Surely yinyang he doesn't need to see a "qualified" tech for this!

I'd disconnect the power supply plug, PRAM battery, and leave it alone for > 24 hours.

JB

stewiesno1
15th June 2007, 10:02 AM
You can't open 'er up and stick your nose in there real close to pinpoint the source of the burning smell ? I've done that before and found fried components - mind you I have a pretty " generous " honker and did it straight away after something failed. Rough guess I would say maybe PSU. The logic boards and CPUs in these old beasts are pretty robust and seldom fail.
Stewie

colinm
15th June 2007, 09:33 PM
You can't open 'er up and stick your nose in there real close to pinpoint the source of the burning smell ? I've done that before and found fried components - mind you I have a pretty " generous " honker and did it straight away after something failed. Rough guess I would say maybe PSU. The logic boards and CPUs in these old beasts are pretty robust and seldom fail.
Stewie

The smell dissipated too quickly - there's no smell now.

All very strange. As suggested, I'll leave it unplugged and without the battery for a day or so and try again - not holding my breath, though. Thanks all!