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Last Post
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Aug 20, 2006 3:51 PM
by: Mac Medic (be@M...
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Posts:
44
Registered:
Jul 17, 2006
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Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 9:37 AM
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Just sent my MacBook into service for the second time because of Random Shutdown. First time I got a new logic board. This next time, before I took it into the Genius Bar, I called up AppleCare to see if there was any known resolution on the Random Shutdown issue. Got directed to a Product Specialist who said that she would send a note to Engineering. I thought ... right. But apparently Engineering got back to her, she made some notes in my case report. Of course, no one at AppleCare would tell me what was in the notes. ???
So, this morning, the Genius tells me that the notes indicated that the thermistor cables may have been damaged when the logic board was replaced. Hadn't heard that before, so, thought I'd post.
Could Random Shutdown be caused by bad "thermistor cables"? Seems as likely as anything else; perhaps the manufacturing process tended to damage some as they were made. And during repair, they were also damaged. Who knows. Maybe Engineering took a wild guess. Maybe there's no such thing as "thermistor cables".
I'll post more when I get the box back; supposedly since this is a re-repair, it gets a higher priority. But they also couldn't repair it in store, no thermistor cables (or whatever). So it's off to Tennessee.
MacBook, White Mac OS X (10.4.7)
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Apr 4, 2003
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Re: Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 9:48 AM
in response to: pmuellr
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I'm printing this post out and enclosing it with my Macbook box when I ship it in. Hopefully I can get a reliable computer again - I really can't afford sending it in 2-3 times 
13" White Macbook
Mac OS X (10.4.6)
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Posts:
6,581
From:
Central WI, Oshkosh 'B Gosh
Registered:
Aug 2, 2002
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Re: Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 10:13 AM
in response to: pmuellr
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Interesting. This shutdown problem could be caused by a defective thermistor on the logic board. A thermistor is a type of resistor used to measure temperature changes, relying on the change in its resistance with changing temperature. If the thermistor is not working properly, it most certainly could trigger a shutdown.
-Bmer
Mac Owners Support Group
Join Us @ MacOSG.com
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2.0 MacBook • 4H620 • 100GB HD • 2GB RAM
Mac OS X (10.4.7)
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178
From:
Now living in sunny Spain
Registered:
Jul 1, 2005
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Re: Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 11:13 AM
in response to: Mac Medic (be@M...
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mine came back yesterday from repair.
the logic board was NOT replaced.
however the thermal assy & lollipop (?) was.
robin..
macbook 2.00 , 2gb ram, 80 gb hd
Mac OS X (10.4.7)
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May 26, 2006
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Re: Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 11:18 AM
in response to: Robin Bonathan
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thermal assembly....sure points in the right direction....
wonder what lollipop could be....
did you happen to leave a lollipop in the optical drive perhaps?
Yellow CrashBook 2.0Ghz
Mac OS X (10.4.6)
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Posts:
167
Registered:
Aug 7, 2006
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Re: Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 11:48 AM
in response to: pmuellr
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The random shutdown could easily be a malfuntion of one of the multiple thermal sensing solutions (not all are diode-based) in the new Intel processors OR on the logic board (yes, there are often several on the logic board). Thermal "trip" is an instant shutdown of a system intended to avoid "catastrophic" failure of components due to a poor thermal design implimentation. As I said, random shutdowns could easily be a malfunction of this protection. Please read the following, I may post it in a main thread as well...
From intel.com's technical documentation on their Core Duo processors:
http://download.intel.com/design/mobile/datashts/30922104.pdf
Quotes From Chapter 5.1.3:
"The Intel Thermal Monitor helps control the processor temperature by activating the TCC (Thermal Control Circuit) when the processor silicon reaches its maximum operating temperature."
"With a properly designed and characterized thermal solution, it is anticipated that the TCC would only be activated for very short periods of time when running the most power intensive applications."
"An under-designed thermal solution that is not able to prevent excessive activation of the TCC in the anticipated ambient environment may cause a noticeable performance loss, and may affect the long-term reliability of the processor."
"An external signal, PROCHOT# (processor hot) is asserted when the processor detects that its temperature is above the thermal trip point."
"If the platform thermal solution is not able to maintain the processor junction temperature within the maximum specification, the system must initiate an orderly shutdown to prevent damage."
"Regardless of enabling the automatic or on-demand modes, in the event of a catastrophic cooling failure, the processor will automatically shut down when the silicon has reached a temperature of approximately 125C. At this point the THERMTRIP# signal will go active. THERMTRIP# activation is independent of processor activity and does not generate any bus cycles. When THERMTRIP# is asserted, the processor core voltage must be shut down within the time specified in Chapter 3 (500ms)."
MacBook 1.83ghz
Mac OS X (10.4.7)
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1,407
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Sep 6, 2001
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Re: Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 12:50 PM
in response to: brwnx
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did you happen to leave a lollipop in the optical drive perhaps?
lol - classic!
Quicksilver G4 733MHz / G5 1.8 DP / G5 2.0 DP / Whitebook 2.0
Mac OS X (10.4.7)
10 GB iPod / 4 GB Mini / 4 GB Nano / the list goes on...
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Posts:
6,581
From:
Central WI, Oshkosh 'B Gosh
Registered:
Aug 2, 2002
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Posts:
167
Registered:
Aug 7, 2006
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Re: Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 1:12 PM
in response to: Mac Medic (be@M...
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Please tell me you were repairing 8-track equipment MORE than just a few years back...  Any random shutdown issues in those?
MacBook 1.83ghz
Mac OS X (10.4.7)
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44
Registered:
Jul 17, 2006
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Re: Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 1:14 PM
in response to: Mac Medic (be@M...
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I had a PC that eventually had a problem reading disks (3.5", if you remember those). Swapped it out, and when I did, realized their were a bunch of coins in it. Gave the boys a little lesson that day to NOT put things in slots on machines unless we said it was ok.
MacBook, White Mac OS X (10.4.7)
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Posts:
178
From:
Now living in sunny Spain
Registered:
Jul 1, 2005
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Re: Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 1:41 PM
in response to: Mac Medic (be@M...
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hi
yes i have the reciept :-
parts replaced :-
top case 922-6869
bezel 603-9857
thermal assy 922-7379
lollipop 603-8320
robin..
macbook 2.00 , 2gb ram, 80 gb hd
Mac OS X (10.4.7)
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Posts:
6,581
From:
Central WI, Oshkosh 'B Gosh
Registered:
Aug 2, 2002
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Re: Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 1:44 PM
in response to: tfurr0ws
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Please tell me you were repairing 8-track equipment
MORE than just a few years back...
Ya, I guess the 8-tracks were back in the 70s. Boy how time flies...eh?  A good friend of mine used to go to K-Mart every week and buy new 8-track tapes. It was an addiction. He had a couple of suitcases in his trunk full of them. 
Any random
shutdown issues in those?
I replaced a LOT of thermistors in television sets. When they went bad, the degaussing circuit stopped working and the CRT's color purity would get all screwed up. I could tell the thermistor was bad when I walked in the door and looked at the screen.
I had a PC that eventually had a problem reading disks (3.5", if you >remember those). Swapped it out, and when I did, realized their were a >bunch of coins in it. Gave the boys a little lesson that day to NOT put things >in slots on machines unless we said it was ok.
Oh yes. Coins were VERY popular. 
parts replaced :-
top case 922-6869
bezel 603-9857
thermal assy 922-7379
lollipop 603-8320
robin.
Thanks Robin!
-Bmer
Mac Owners Support Group
Join Us @ MacOSG.com
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2.0 MacBook • 4H620 • 100GB HD • 2GB RAM
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Aug 7, 2006
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Re: Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 2:12 PM
in response to: Robin Bonathan
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Great, now we all have to wonder what kind of confectionary delight is hidden inside our shiny black/white casing...
Just how many licks DOES it take to get to the center of a MacBook? The world may never know...
MacBook 1.83ghz
Mac OS X (10.4.7)
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5
Registered:
Aug 8, 2006
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Re: Random Shutdown (theory | wild guess) - thermistor
Posted:
Aug 11, 2006 2:14 PM
in response to: Robin Bonathan
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Robin,
What did your problem description read when you sent it in? Mine says "won't run off AC power" which isn't the problem at all because once its started i don't have to have it plugged in. Grah!
Brenda
macbook
Mac OS X (10.4.7)
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