Pismo Heatsink Questions

[kkritsilas]

Hi,

Slowly getting to work on my Pismo (currently non-functional) by getting the memory modules replaced/upgraded. For a refresher, I got this from a local electronics recycler for $12, but it was incomplete (missing RF shield over the the CPU card, no HD bracket or cable, no charger). It is the basic Pismo, 400MHz CPU, 64MB Ram, originally had a 10GB HD, DVD ROM in the right side bay, and a battery in the left side bay). In removing the CPU board to replace the RAM module, I removed the heat sink plate (two small screws over what I think is the CPU, one long screw that holds down the rest of the heat sink assembly). The bottom of the heat sink plate (the part that fits over the CPU) did not have thermal compound, but a black thermal pad. I put the new 512MB modules in, added the replacement IDE cable, and then replaced the CPU board, and temporarily put the heat sink assembly back. What is the correct thermal material to use on the CPU? Do I need to use another thermal pad, or can I use the usual CPU heat sink compounds from Arctic Silver/Thermaltake/BeCool/etc.? The pad that is on there now seems to have been squashed down pretty hard, so I guess that if I used a thermal pad, it would need to be approximately the same thickness (does anybody know what that is?).

I don't want to try to turn on the Pismo (it was completely dead, as in no power on chime or even the display backlight coming on) prior to my latest efforts, but I also don't want to overheat anything due to my having removed the heat sink and breaking the thermal interface between the CPU and the heatsink.

 

[Phipli]

What is the correct thermal material to use on the CPU? Do I need to use another thermal pad, or can I use the usual CPU heat sink compounds from Arctic Silver/Thermaltake/BeCool/etc.?

Just use the same pad as long as it isn't badly damaged?

I've removed mine a load of times and just put it back.

If it isn't providing enough cooling the fan will come on. The fan on my pismo has never come on, so much so that I once unplugged and tested it to make sure it works.

 

[kkritsilas]

The themal pad doesn't appear to be damaged, just compressed, which is what has me questioning how well it works. It would be great to find a replacement, but I would need to figure out how thick the replacement should be for complete contact with the CPU (I guess its the CPU). Too thin, no contact and no heat transfer. Too thick, and maybe risk bending or breaking something. Decisions, decisions. I may try it anyway to see if it helped fix anything, and not try to run it for any significant amount of time if it powers up.

 

[Phipli]

The themal pad doesn't appear to be damaged, just compressed, which is what has me questioning how well it works. It would be great to find a replacement, but I would need to figure out how thick the replacement should be for complete contact with the CPU (I guess its the CPU). Too thin, no contact and no heat transfer. Too thick, and maybe risk bending or breaking something. Decisions, decisions. I may try it anyway to see if it helped fix anything, and not try to run it for any significant amount of time if it powers up.

It can't be compressed more than the fit of the heatsink. I think you're over thinking it.

An incorrect replacement is more likely to be an issue than what is already there.

 

[kkritsilas]

Well, I put it all back together, and the Pismo is working. Not completely, because it doesn't have a hard drive, but I reassembled it, and hit the power button. AND IT STARTED. I don't know exactly what the issue was, whether it was the oddball memory module in the lower memory slot, or if the CPU board wasn't put back onto its connector properly when whoever had it before removed the IDE cable, but I started it up today, and got a startup chime, and at first a blank grey screen (with 2 X 512MB modules, it takes a while to run the memory test, I guess), and then the folder icon with the flashing question mark appeared in the middle of the screen. Popped an 9.2.2 install CD into the optical drive, and the CD booted into a desktop home screen. I was able to run System Profiler, and all appeared well. I am also able to see the contents of the CD. Still not 100% functional, as it needs storage, and I haven't decided if I will get a mechanical PATA/IDE drive, or if I want to get a PATA SSD, but that is a decision that is now possible.

Thank you for the information and encouragement.

 

[Romko23]

Speaking of pads, what is the apple part number for a G3 Pismo processor pad ? I may want to get some extra ones.

 

[Byrd]

Another Pismo alive! I think a few of us have had luck with resurrecting them once the CPU card reseated, PRAM battery pulled ... the thermal pad can get chalky and disintegrate but if it still looks good I usually wipe it down with an IPA wipe (+ CPU core) and use it time and time again. More modern thermal pads are easily available and appear more resilient if you need to replace.

 

[3lectr1cPPC]

I'd just replace with arctic mx4 or mx5 if the pad is damaged. I usually just replace the pad with paste either way if the pad was thin enough that paste would work, as paste should provide better cooling performance.