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 Post subject: Cooking Hot Even When Off
PostPosted: Sat Sep 20, 2003 6:32 am 
My Pismo/500 is from May 2000, with 512MB RAM and an IBM Travelstar 7200 RPM 40GB drive. The environment is dusty, hot & humid most of the time with salt air. But inside there is no sign of corrosion and only light dust. Even when new, the fan rarely went on, even in this hot climate (the first time was a big surprize).

The DVD drive has been intermittent, after some attempts mount the disc the drive door just pops open. Sometimes immediately after being closed. Sometimes it can be coaxed into working by removing and inserting the drive. I was certain that the drive needed replacing.

Recently I had trouble with the batteries. It would give me the reserve warning when the right side battery was empty, but the left was full. I tried a PMU reset, zapped PRAM, and even did an Open Firmware reset of the NVRAM.The problem reappeared yesterday, so I put it on AC and switched the batteries. When I took the AC off it showed the left side depleted, and the right side full, and gave no reserve power warning.

So I suspected battery and/or PMU trouble.

In the last week, it's seemed to run hotter than normal (and normal is fairly hot), but the fan would never run. Sometimes the AirPort connection would fail. If I let the machine cool off it would become usable again. I thought I might have a dead fan or fan control logic.

Last night I shut it down to let it really cool off, but left it plugged into AC to charge. Lately shutdown takes a long time (several minutes), but I saw it turn off. In the morning the bottom case was hot as though I had been working it hard for hours. I unplugged the AC, removed the keyboard to let it vent, and proped it up on it's side to get more airflow ovearall. The heat shield and heat sink were very hot, but the disk, and AirPort were typically warm. Several hours later it was still hot! I was sure that it was off! This time I pulled the batteries. The right side one was depleted and the left one was full.

One of the bateries is the original, and one had been replaced by AppleCare.

I carefully felt the bottom case for the pattern of heat. It was only mildy warm under the disk drive. The hot spot seemed to be directly under the large IC on the logic board (bottom mounted), and continued left under the processor area to about the extent of the ruberized area.

I've pulled the processor card and visually inspected as much of the logic board as I could see. The are no obvious signs of heat damage on the top side (pin side) of the large IC.

The batteries do charge, so I think that the AC/Sound card & power card are OK, but I am suspicious of the PMU. The fan not running could be the logic card. Could it also be causing the DVD drive symptoms, or is it gone too? (it does wok once it's coaxed into mounting). The heat points to the logic board, but, it's always run a little hot.

Have you ever heard of a machne that is OFF spontaneously turn ON?
How ccould a logic board that is powered off cause such a problem?

I'm buying a new PowerBook, so I don't want to pour much money into this old one, but it's such a good workhorse. How can I best isolate this problem, or tell whether it's a single failure or multiple ones?

What's the likelyhood of a complete disassembly, cleaning and rebuild making the problem just go away? (Do you use anything besides compressed air for cleaning? The salt air can make for sticky & conductive dust....)

Thanks for any advice,

 Post subject:
PostPosted: Sat Sep 20, 2003 10:28 am 
Site Admin

Joined: Mon Feb 24, 2003 1:58 am
Posts: 940
The heat is generated from your processor, and it's a good possiblilty that a component on your processor has failed. Your fan could be bad as well, but from the symptoms you describe it is most likely the processor. There is a chance the logic board or PMU are to blame, but we'd need the unit in the shop to verfiy. The processor would be a good starting place though.


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