IT8000 fan noise
Posted 24 April 2012 - 11:13 AM
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Visit us at: http://www.schnakesound.com
Posted 21 August 2012 - 03:08 AM
Posted 22 August 2012 - 02:30 AM
Do you need to actually first take the thermistor out of the circuit board and only then measure its resistance or you think the method mentioned the following link (the reply by Moby (Mike Diack)) is just as good?
Do you have pictures of the itech internals? More specifically of the four thermistors?
Posted 30 August 2012 - 03:25 PM
To test out the SMPS thermal sensors:
First, get access to the SMPS control board: This board is located beneath the EMI filter board (The EMI module is the top most board when the cover is removed). Be careful when removing the EMI module!
Then remove the control card. It is the long card (6" x 2"), with a multipin header on the bottom middle edge. It is also aligned with the power rail connector.
Note: The reason I remove the control card is that the sensors' load are 'connected' to the control card and can cause misreadings.
On the main board locate the thermistor's connector; The other end leads to the thermistor, located on the SMPS heatsink.
Now you can test the thermistors via the connector! Cold, both should read the same, around 20K. If one of the components is way off then both thermistors will need to be replaced.
Hope this helps! Let me know if you still need the pictures!
Posted 18 October 2012 - 12:07 PM
What you have surrounded in red is the USP3T (network) card!
The SMPS is located to the left of the picture, under where the metal grill is located.
There are a few screws to remove the grill and to get to the EMI board. Underneath the EMI board is the SMPS module.
CAREFULLY remove the EMI module; Notice the paper isolator stuck to the grill. CAREFULLY rmove the paper isolator. Once the EMI module is removed, then you now have access to the SMPS. Note: The side flaps of the isolator should be re-positionned between the heatsink and smps gate drive cards, to prevent the smps gate drive cards to short out on the heatsink.
The thermal sensors should now be visible, located on the far side of the heatsinks, in front of the fan. Two pair of wires run from the sensors to two connectors on the board. You can now measure the sensor at the connector. I suggest to remove the controller card so that the measurement isn't influenced by the impedance of the controller card. It should be arounf 20K ohms.
I would highly recommend that an experienced tech take a look at the unit. No offense!
I hope this helps!
Posted 18 October 2012 - 02:55 PM
The thermistors values were 7.54K and 6.88K. If I understand correctly they should measure in the 7K neighberhood.
I measured the values on the two small white, two wire connectors:
Posted 19 October 2012 - 08:51 AM
There's a long board next to the two round blue discs (PTC: positive temperature coefficient resistor) to the right of the pictures. This is the smps controllor card. Among other things, it manages the temperature and fan control via the smps and bca sensors. Since the sensors are connected to the card, by removing the card you will have a better view (measurement) of the sensors. They should measure around 20K with the controllor card removed.
On the bca side, you will have to remove the front-end cards to better measure the bca sensors.
Note1: PTC: resistance is normally low (6 ohms) and its resistance will increase while the component heats up; usually applied instead of a fuse! Also, used in soft start circuit;
Note2: If the PTCs should measure normal and the fans 'modulate' (somewhat evenly!) with the power going though the output module, then I would say that the sensors are pretty good! A bad sensor will continue to modulate the fans at high speed even if the power to the output modules is removed.