Murphy's law - CPU thermal paste applied, no more video

[somedude]

This is one of those situations where Murphy is watching and having some fun.

I have been slowly trying to revive this 6100 and I finally got video to display.

After running it for s short while I noticed that the CPU was pretty hot, so I decided to reapply thermal paste, as I read that the original cooks up.

Done. With Arctic Silver under the heatsink, I can already feel that the CPU is cooler.

Here's the "however" - no more video.

I get the chime but I no longer hear it trying to access the CD.

Any ideas what could have gone wrong?

I removed the main board for this purpose and reconnected everything back.

There was a tiny bit of old grease that touched the pins of the CPU - is this stuff conductive?

I tried, but couldn't get it all off.

I am sure that all the connectors are in right.

EDIT: SOLVED

Note to self: Remember to put in the PRAM battery!!!

 

[PowerPup]

Yes, the PowerMac 6100 won't boot up properly without a working PRAM battery.

If you ever find yourself without a working PRAM battery, you can do the power toggle trick.

Turn it on for a sec, then quickly turn it off and back on again. Should get the video working and booting up normally.

Edit: Also, yes Arctic Silver 5 is (somewhat?) conductive. So one needs to make sure any mess is cleaned up before booting.

 

[somedude]

Thank you.

I actually smeared the original "grease" - the white stuff, not the AS, which I know can cause trouble.

I never managed to do the double-tap with the power switch.

I gave up, though, as it was hurting me to put the poor ol' machine through that ordeal...

 

[trag]

I actually smeared the original "grease" - the white stuff, not the AS, which I know can cause trouble.

Most, if not all of greases are conductive. I once killed a PCC Power 120 board by getting heat sink grease on the pins. The Power 120 is a PM8100 clone.

Interestingly, before dieing, the machine worked fine except in HOMMII the lightning bolt zap didn't draw correctly. Back then, everything I did to clean off the grease made it worse. If I'd left it alone, it probably would still work. Those pins are so fine and the grease so tenacious.

From now, with more experience, I think the thing to do is to completely remove the board from the case and empty it of SIMMs (RAM) and DIMMs (ROM and cache) and heat sink, then clean the top of the CPU normally; this is to reduce runoff in the next step. Finally get a spray solvent that is safe for circuit boards, such as Flux-Off, and spray the grease off the pins. A gentle brushing with soft bristles in line with the pins, never across them, might also be needed.

But if it's working now, leaving it alone is an attractive bet.

 

[somedude]

Thanks trag,

I will likely open it up again because the CPU is far too hot for my liking and I will try to find a heftier heatsink and adapt it in there.

Maybe even throw a fan on it, as I have one of those hdd power pass-through dongles with a fan connector on it.

Just have to find a quiet one as the Mac is pretty silent right now, though I am missing the hdd.