15" PB 1.67 - Location of "Power Supply" temperature sensor inside the laptop?

[burnout8488]

Created another thread with a more concise question...

My Power Supply temp sensor fluctuates wildly causing improper fan engagement. Usually from 40ºC - 80ºC, depending on if the trackpad is moved around. Very odd.

My guess is that it's on the DC-in board, but I don't want to buy one unless I *know* it is the problem. If its on the logic board, it would help knowing that too.

Hope someone can help! 🙁

Photobucket Video, turn up the volume so you can hear the fans going as I scroll:



When I scroll, the temp sensor spikes to 75-80ºC, causing fan engagement. When I let off, the temp sensor goes back down, turning the fan off. I have no idea what the actual temperature is around this sensor, unfortunately.

 

[burnout8488]

Anyone? 🙁

 

[666sheep]

I don't have precise answer yet, but let's try to clarify whole thing a bit...

In this thread https://forums.macrumors.com/threads/1296968/ you've said that:

It looks like the "Power Supply" temperature sensor (Sensor 3 in the photo) may be causing the problem. It jumps around all over the place whenever I move the my finger around on the trackpad

PSU sensor is described as Power Supply Bottomside (in Temperature Monitor), so it's presumably located on underside of logic board.

That what I've quoted would inicate that Sensor 3 is rather trackpad thermal sensor (I know that on G4Fan site S3 is described as PSU sensor ofc). Trackpad sensor failure was common issue of Alu PB's but symptoms were quite different...

Maybe it's basic question, but did you reset PMU and PRAM after replacing top case?

 

[burnout8488]

Thanks for your insight!

I should have been more clear.

The "Power Supply" temperature sensor (what it says in iStat widget) will go crazy not only when I scroll, but if I move an external mouse, or put any type of load on the system. If there is any sort of CPU draw (scrolling the trackpad is one thing that causes it) the temp sensor will jump around and make the fan go nuts.

The sensor labeled "Trackpad" in my iStat widget stays stable and does not fluctuate very much at all. In the G4FanControl app, the trackpad is not listed as one of the sensors nor does the temperature of the trackpad correlate with any of the temperatures in G4Fancontrol...leading me to believe the Trackpad sensor does not influence the fan speed in this Mac.

I do not have any of the narcoleptic PB symptoms that some users do when their trackpad sensors go bad.

The Power Supply temp sensor would lead me to believe it's on the DC-in board, but since that gets no airflow from the fan, it makes sense that it would be somewhere on the bottom of the logic board. Just wish I could repair it, or eliminate it entirely!

 

[666sheep]

IDK if it's helpful, but temp sensor used in MDD daughtercard looks like this:

.

2 legs on one side, 3 legs on other. DP MDD dcard has 2 of these. ATM I don't have a magnifying glass by the hand to see what's printed on them (I have few MDD dcards in my stuff box) but I'll try to decipher it tomorrow.

Look for identical SMD part on your PB's logic board. It would be what you're looking for.

Edit:
another thought - there's a small chance that's software issue. 7455 and 7447 are communicating with OS using temperature sensor and there's a kext which controls fans speed (http://bitsandpieces.info/MDDFanExtensionMod.htm). I think it works this way in PBs too. Before disassembling whole unit try clean OS installation.

 

[burnout8488]

Interesting! Very cool link. So in my PB, there is a chance this "Power Supply" sensor is somewhere near the CPU then.

This began prior to (When I bought the laptop a few weeks ago) and immediately after a fresh install of 10.5. Does that rule out software being the issue?

 

[666sheep]

Interesting! Very cool link. So in my PB, there is a chance this "Power Supply" sensor is somewhere near the CPU then.

Not exactly. Near CPU you should find 2 sensors: Processor Bottomside and Processor/Controller Bottomside. PSU Bottomside sensor should be located (I guess) near the DC-in board.

This began prior to (When I bought the laptop a few weeks ago) and immediately after a fresh install of 10.5. Does that rule out software being the issue?

Completely.

Edit: thermal sensor on MDD daughtercard turned out to be DS1775R1. It has printed 7751 on the top.
datasheet to download