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Model A1224 / Mid 2007 및 Early 2008 / 2, 2.4, 또는 2.66 GHz Core 2 Duo 프로세서

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Searching TG0H: Heat-sink Sensor ATI Radeon HD 2400 XT.

Hello,

since three days the cpu fan of my iMac runs constantly at 3900rpm short after the start. I've done SMC and PRAM-Reset without a result.

Then I made an ASD to precisely check which device is causing this problem. ASD activity log file shows following failures:

[05:26:56] ERROR - -13009 [SMC error TM_TEMP_BELOW_MIN, the temperature read from the sensor is too frequently below some minimum threshold.] -- (1.00)

TEST FAILED

[29 Apr 2010 05:26:57] SMC: SMC PID Sensor check (test #1) - SMC PID Sensor check

- Checks the SMC PID Sensor warning counter that is monitoring sensors of each PID loop for erratic behaviour.

[05:26:57] ERROR -- 1 [The SMC's PID Sensor check has been tripped] --

TEST FAILED

Hardware Info shows

Sensor

type: Temperature

Location: Temp (TG0H) - GPU 0 Heatsync

Low limit: 10 C

high limit: 105 C

reading: 1.00 C

description: GPU 0 heatsink temperature

The GPU heatsink sensor is reading only 1°C. I think this causes the fan ramping to 3900rpm. But I found out (thanks to Richdave) that this GPU sensor is not available seperatly, so the support got to change the whole VGA – but that's too expensive for me. I've bought an thermal adhesive and thermal paste, now I need the correct temp sensor. All I know is that it should be a TO-92 and it must have low limit 10°C and high limit 105°C.

Does anyone which temp sensor is used in the heat-sink of ATI Radeon? Or can s.o. sell me an ATI Radeon? It could be also broken at least, because there are three identical sensors used (TG0D, TG0H, TG0P).

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I have been doing some research and the device is likely something similar to the Dallas Semiconductor DS1822-PAR device. It is a TO92 package and operates as a 2 wire device powered only by the "HIGH" transition on the data-line. The 3rd pin is not internally connected so I suspect it is joined to the DQ (data) pin rather than clipping it off when the sensor assy is made. This device is stocked by mouser.com and probably many other suppliers too.

You will only be able to confirm the exact device if you extract it from the heat-sink assy. Since you have already found a low thermal resistance adhesive, perhaps it is worth doing?

My only concern about this device is the data sheet refers to each device’s unique 64-bit code suggesting that it is an addressable device. If so then you probably need an OEM device.

Another option may be to swap the cables between the GPU and the CPU sensors. The CPU cable looks like it will reach the GPU connector but the GPU cable will not reach the CPU connector.

I expect these are exactly the same; however without testing I cannot confirm this and they are addressable devices; however further reading suggests the system interrogates and learns the address of each device so perhaps there is not going to be a problem swapping them.

If you do this and you get a valid test on the GPU and the CPU failing that confirms the logic board is OK, leaving the GPU sensor as the fault.

If you get the GPU failing and the CPU failing that suggests the logic board is faulty.

If you get the GPU failing and the CPU passing, it most likely means the device is not interchangeable and you need a OEM sensor to replace the faulty one.

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The thread you link to is where I was posting in :) (InteractionDsgn)

The GPU is not soldered to the logic board – it can be replaced. I own a Service Manual for my iMac and it is precisly shown how to replace the video card. The GPU temp sensor is glued into the GPU heatsink and pluged onto the MLB. It is a TO-92 semiconductor temp sensor. But I need to know which one exactly. Then I can replace it and fix it with low thermal resistant glue.

btw: Are you from D?

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mea culpa - mea maxima culpa - asche über mein haupt (womit die frage der herkunft geklärt wäre) your right - after i've read your posting i looked inside the manual - and voilà - there it is, the graphics card

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first of all - here are a few things about the sensor problems with that iMac generation.

->[afaik - the gpu is still soldered to the logicboard, you can't change it.]<-

scrap that, thanks InteractionDsgn for the hint with the service manual (i should start to read them again)

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Hey Richdave,

I've bought a new Heatsink for the ATI Radeon (10€) and I'm gonna going to replace the old heatsink /w sensor. I don't think that the MLB is faulty since all test (mine and Apple Service provider) only show up the Sensor problem, further there's no need to change the gpu/cpu cables.

Because the vga heatsink replacement will be my first teardown I would be happy if someone could share his experience here. I'm especially a little bit nervous about handling the logic board and replacing the old thermal paste. What solvent can I use? The new thermal paste will be Arctic Cooling MX-3. Any best practices would be great.

PS: In the service manual they mention an anti-statical mat to use. What else can I use to put the parts (logic board etc.) in during the replacement.

Thanks.

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First of all dont rush! I think that you can remove the VGA without taking the logic board out but need to confirm this for you.

As far as removing the old thermal compound goes, if it is a paste then just wipe it off and clean up residue with Methylated spirits or similar. If it is a thermal pad (like double sided tape) then you may need to use a plastic spudger or similar to gently scrape the old pad off and then clean as before.

The thermal compound you selected will be fine, there are many and all will be suitable. There is a lot of hype about certain brands. Apply a small amount (match head) to the centre of the GPU and spread it evenly over the surface. Too much is as bad as too little so don't go overboard. It should be thick enough so it is not translucent but only just. I use my finger in a rubber glove but some suggest a piece of business card or similar to get it even and flat. Don't allow it to spill over the sides onto the surrounding components.

THIS may help

As for the anti static, I'd suggest you get at least a wrist strap, they are cheap and will ensure you are grounded to the metal frame of the iMac while you remove the parts. If you don't have one, remove any materials that are likely to create static while you work and ensure you touch the metal frame of the iMac before you remove or install the board to discharge any static charge on your body. I've seen a sheet of aluminium foil wrapped over a foam sheet and connected to the frame of the equipment with a clip lead used as a "grounded" work surface. Avoid plastic, fabrics, and even paper as a work surface as they can easily create static charges. A simple wooden surface will do. Also try not to work in a carpeted area as this can also cause static charges on you as you work/shuffle your feet. Anti static precautions are certainly best practice however most modern devices are reasonably resilient and have built in protection on inputs

There is a guide HERE for thermal paste as well

Yeah the Logic Board has to come out and be flipped over to remove the VGA. I was picturing the logic board the other way up for some silly reason... guess I have had the board out to many times (or not enough??) Anyway there is a good guide HERE

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Thanks! At most I fear taking out the logic board since it's the most expensive part of my iMac. I'm also a little bit more exicted about putting the iMac together again. :)

"Anti static precautions are certainly best practice however most modern devices are reasonably resilient and have built in protection on inputs" - Yes I think in that way too. But you know: Better safe than sorry. I've linoleum all over my flat, so i guess it will be the best to work barefooted. Where do you put your logic board after teardown? And to which side do you lay it down?

Thanks!

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LOL working bare foot! Well you need to put the logic board down with the memory slots facing down so you can take off the VGA card. I assume you have a table or whatever so as long as you have a prepared clear space it will be OK. Just remember when working to take off/install the VGA you don't bend or flex the logic board. And make sure you "touch off" on the metal frame of the iMac often to dissipate any possible static you may build up.

Taking the logic board out is easy as long as you follow the procedure and are careful. Slow and steady is the trick. Putting it back the only trap I found was that I routed the mic cable around the board support so it was too short and had to pull the board a out again! make sure the mic cable runs between the ODD fan and the board support

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wondering how the swap out is progressing.

BTW, are you able to carefully extract the sensor from the old HS assy and advise what device it is please?

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Hi, sorry I was very busy at the weekend. The teardown is starting today afternoon because the thermal paste will come in today – I will document every step carefully.

Oh yes, and when I've replaced the old heatsink and the iMac will run fine I'll extract the sensor and report what device it's precisely.

----- Important -----

One more question: In the ifixit video card manual for intel iMac they only say to apply a new goop of thermal paste on the old. Can anyone confirm this? I always thought the old paste have to be removed.

---------------------

Thanks for the micro cable hint.

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REMOVE the old and clean the heat-sink and GPU chip surface before applying new thermal compound. Good luck. I'll try to keep a close eye on this thread in case you post any questions

I just looked at the "installing iMac intel emc 2133 and 2210 video card" procedure and it is a little ambiguous but it does have a link to the "Installing Computer Thermal Paste" guide which does state to clean off old compound.

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Hey, I've made it – I changed the heatsink with the help of my beautiful girl. The first time I reassembled the iMac I forgot to plug in the GPU sensor cable :) I've tore-down it a second time – this time I get all cables plugged. I started the iMac and during boot-up the cpu fan began to run very loud - same old problem. Run ASD it shows:

[10 May 2010 23:51:54] Temp (TG0H) - GPU 0 Heatsync (test #1) - Sensor Reads Within Operating Range

- Check to ensure that sensor reads within operating range.

[23:51:54] ERROR - -13009 [SMC error TM_TEMP_BELOW_MIN, the temperature read from the sensor is too frequently below some minimum threshold.] -- (1.00) TEST FAILED

[10 May 2010 23:51:55] SMC: SMC PID Sensor check (test #1) - SMC PID Sensor check

- Checks the SMC PID Sensor warning counter that is monitoring sensors of each PID loop for erratic behaviour.

[23:51:55] ERROR -- 1 [The SMC's PID Sensor check has been tripped] -- TEST FAILED

That are exactly the same I got with the old heatsink. Now I guess it's not the sensor but maybe the logic board – this gettin me down. What do you think about it?

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Hmm yeah it does seem that way! You may want to reset the SMC and try again just in case... Assuming I am correct about these sensors being addressable and being similar to the DS1822, the system "learns" the unique ID of each sensor. Perhaps resetting the SMC will force this to happen?? Otherwise if it were me I would be plugging the CPU sensor into the GPU connector and seeing if I still get a valid CPU heat-sink temp reading. (I am assuming the sensor is addressable thus it will still return the data as CPU not GPU) That will confirm the path between the connector and "smc" circuitry are ok.

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"Hmm yeah it does seem that way!" This would be really bad. The curious thing is, that the iMac is working perfectly – I mean it's only the cpu fan and this louder noise that is disturbing. Yeseterday I got my new CS5 Design Premium – it's runing very well. IS there any way to overwrite the smc commands for the cpu fan? Smcfancontrol doesn't work.

What do you think it could be, when the path between the connector and "smc" circuitry are ok? Do you think it's worth the work or better to sell it in the bay as defect (although everything is running very well).

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Yes you can change the fan speed manually however it is not permanent, that is a reboot or wake from sleep will see the fans go back to default speeds - in your case FAST. I'll post detail soon. I have no detail on the circuit or devices used by the "smc" so cannot help on that front. The only way I can see to do further testing IMO is to try the CPU sensor in the GPU connector. If you get a temperature reading it will at least prove the physical connection between the connector and the "smc" are ok. Is it possible the HS you bought also has a faulty sensor? Did you try a smc reset? long shot but a PRAM reset too can't hurt.

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To manually set the CPU fan speed you need the smcFanControl app and know where it is on your system (directory location)

  1. Open Terminal
  2. cd to the folder containing the smcFanControl.app
  3. cd smcFanControl.app/Contents/Resources
  4. type ./smc -k F2Mx -w 1770 (note the . before the /)

The above command will set Fan 2 max speed (F2Mx = CPU fan maximum speed on 2008 iMacs) to 1500rpm. The value after the -w is the fan required fan speed x 4, then converted to hex (1500x4=6000d = 1770h) As stated earlier, these changes are not permenant and will revert to defaults upon reboot or exiting sleep mode.

Use CAUTION when using the -w switch as it writes without any confirmation!!

./smc ? will list other options.

./smc -f will list details about all fans

./smc -l will list all available smc keys.

FYI F0 is the ODD fan, F1 is the HDD fan in 2008 iMacs.

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Hi, thanks I've managed to slow down the cpu fan to 1800rpm. Well which GPU/CPU temps are normal? Now I can work with my iMac again. Hmm I'll try the change of the CPU cable later the week.

I've also made an AppleScript to slow down the cpu to 1800rpm after restart or sleeping mode.

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good o. Care to share it? Keep us posted on any developments

Any news on your system?

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Any news on your system?

Would you share the script you made?

Having the same problems here.

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