Help! G4 FW800 won't boot

[sm8000]

Disclaimer: I'm not a Mac guy, so I might need my hand held and to be walked through any suggestions.

I am helping my sister sell her old G4 FW800 MDD with dual 1.42s. Last night she came over, got her files, then wiped and reinstalled 10.4 fresh onto it. Everything was fine.

I should have left well enough alone but that CPU fan noise was bugging me. I opened it up, unscrewed the heatsink, cleaned off the old gunk (didn't touch the CPUs) and applied some Arctic Silver 5.

Ever since then, it wouldn't boot. At first it would sound the startup chime, but no image would appear on screen. Eventually the system would turn off.

I then tried Cmd+Opt+P+R, but no luck. I also tried Ctrl+Alt+Shift, no effect.

After this it started booting up, no startup sound, fans kick into overdrive until I shut it off. This morning I located the PMU button, hit it and tried booting again, same thing.

Help!

 

[Avenger2SER]

Check that the heatsink is snug up against the cpu board. Sounds like it's overheating. Also check that the cpu hasn't popped out a bit when you removed the heatsink.

 

[harryb2448]

And write 1,000 times 'I must not dismantle my sister's Mac'.

 

[sm8000]

Check that the heatsink is snug up against the cpu board. Sounds like it's overheating. Also check that the cpu hasn't popped out a bit when you removed the heatsink.

I unscrewed and rescrewed the heatsink and made sure all five screws were tight. No change in behavior.

I really don't know how to get the dual CPUs out of their little daughterboard, if you can, nor do I know how to remove that board. It does wiggle in place a little bit, and if I push down it does bend down a bit, maybe it should be more snug to the logic board?

 

[Avenger2SER]

Did you change anything else on the system? I've seen this happen when I unplugged the slave drive and didn't change the jumpers on the master to cable select (varies by drive as well). This was on a Dual 867 MDD, so very similar to yours.

 

[sm8000]

Not at all, didn't touch any cables, jumpers or drives. The only thing I did before this began was unscrew the heatsink, apply AS5 and reattach the heatsink.

 

[Avenger2SER]

Just popped back to my marketting dept where we still have a MDD dual machine, take a look at the heatsink and make sure everything matches up to yours (screws etc). This cpu has never been touched.

 

[sm8000]

Thanks, I will compare after I get home tonight or tomorrow.

 

[harryb2448]

Cleaning off the original Arctic Silver is critical, and if the CPU's are loose, they should come off and be cleaned also. There is a commercial product advertised on eBay etc that is supposed to be pretty good for removing the sealant.

For what it is worth, for fan noise best to start at the front fan, near the front leg, and make sure it is spotlessly clean as dust and junk do build up there. Go through other fan units and it is possible to replace any failed units.

 

[sm8000]

Figured out how to unseat and reseat the daughtercard, cleaned the AS5 off the CPU cores and heatsink with 91% isopropyl alcohol. Reseated the daughtercard, reattached the heatsink, no change

 

[Avenger2SER]

Unplug the hard drive(s) and attempt to boot.

 

[sm8000]

Just tried that, no change.

 

[Avenger2SER]

Try taking out memory one chip at a time and booting each time.

 

[sm8000]

Already tried that a couple of days ago, no luck.

 

[Avenger2SER]

I'm out of ideas. Hopefully there isn't any damage to the logic board or cpu. If I think of anything else I'll post back.

 

[sm8000]

Thanks for your help. At another forum it's been suggested that I check the PSU voltages. I'll post back with any updates.

 

[harryb2448]

And after that only one suggestion. "Sis he killed it!"

 

[sm8000]

After a long and busy weekend, I finally had time to compare your photos to the G4 on my hands. I noticed I made a mistake when I remounted the heatsink.

In the last two photos, see the flap of metal bridging the I/O ports to the heatsink? Well I had remounted the heatsink such that the flap was under the lip of the heatsink and not over.

I remounted it correctly and fired it up, but no change in behavior. I unmounted the heatsink again to make sure the CPU card was mounted correctly. I remounted that and the heatsink, and tried again. This time it turned off after a few seconds. Tried again, same thing and I began to smell smoke

Upon inspection it appears I chipped the corner of one core when remounting the heatsink the right way. Needless to say I am the high bidder on this.

 

[harryb2448]

Well fingers crossed for you and back to the blackboard "I must not ....................."

 

[Avenger2SER]

Good luck