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Electronics => Repair => Topic started by: freyz on February 03, 2021, 11:18:47 pm

Title: Plz help identify burnout resistor on thrustmaster t500 pcb
Post by: freyz on February 03, 2021, 11:18:47 pm
I am trying to save my Thrustmaster racing wheel after its motor stopped responding. I found a burned resistor on the mainboard that seemingly caused the issue. However, I don't understand its function and its marks all fade out.  [attachimg=1][attach=2]
According to multimeter measurement, the resistor is between 24V positive and H-bridge motor controller. I don't see why such resistor is needed since both motor and MOSFET are rated for 24V. When I short the resistor the motor did rotate and work just fine. So my question is, what is this resistor and do I really need to replace it?
This is the rough schematic about the resistor.[attachimg=3]
Title: Re: Plz help identify burnout resistor on motor controller
Post by: techneut on February 03, 2021, 11:32:44 pm
It is possible that the resistor is used for current sensing. It will then be around 1 Ohm or less.
Title: Re: Plz help identify burnout resistor on motor controller
Post by: freyz on February 03, 2021, 11:54:35 pm
That makes a lot of sense. Is there still a way to figure out the exact resistance?
Title: Re: Plz help identify burnout resistor on motor controller
Post by: fzabkar on February 03, 2021, 11:59:06 pm
I'm wondering if it is a fusible resistor.
Title: Re: Plz help identify burnout resistor on motor controller
Post by: fcb on February 04, 2021, 12:12:14 am
See if there are some teardown pix on the interwebs of your exact model or ask someone to open one up and photograph the board.  The resistor colour code will allow you to work out exact value.

If it was a fusible resistor it wouldn't have burnt like that.  Also, worth checking the FET's / motor /wiring - the resistor is likely to be a symptom of the fault not the cause.
Title: Re: Plz help identify burnout resistor thrustmaster t500 pcb
Post by: freyz on February 04, 2021, 01:00:15 am
The best photo I can find is this... But I don't know what it should read. I never seen a resistor beginning and ending with black. Do you have any idea?
Title: Re: Plz help identify burnout resistor on thrustmaster t500 pcb
Post by: picburner on February 04, 2021, 08:30:46 am
From Queen Mao Electronics (https://www.queenmao.com.tw/resistor_color_code.htm): "Generally, If an additional fifth band is black, the resistor is wirewound resistor"
and from Digi-Key (https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-resistor-color-code) resistor code calculator the resistor is 0.03ohm 1% that, given where it is placed, it might make sense.
 
Title: Re: Plz help identify burnout resistor on thrustmaster t500 pcb
Post by: fcb on February 04, 2021, 11:56:05 am
0.03 ohms seems pretty reasonable for that posistion.  But to burn it out you're talking perhaps a couple of watts for awhile.

P=I2R, so 2W would be 8.16A. Expect there to be another fault somewhere (blown FET?).