My boy broke his steering wheel... Electronic help!

Hi everyone, Luke’s broken his Driving Force GT steering wheel.
He’s probably done it by over enthusiastically using it when not plugged in.
Inside the wheel is a force feedback motor that provides, well, force feedback. I’ve popped open the cover to see what’s going on inside.
Symptoms are that the GT logo flashes. This indicates a fault.
It’s supposed to calibrate when powered up bu turning full left then full right then back to the centre. What it actually does is turn full left, then pause, then kick a couple of times.
I believe that maybe he’s fried a MOSFET by turning the wheel too fast when not plugged into the pc, generating a bit too much back end from the feedback motor and frying one of the MOSFETs - whichever one it is that turns the wheel right.
It looks like there’s some kind of diode behind the motor connector too - is that maybe designed to stop what he’s done to the MOSFETs? Has he blown that up too?

Does this all make sense?

They are SO-8 packages. Is it feasible to replace them? I’ve never really done surface mount soldering before.

Also, with the motor plugged in it’s easier to turn left than it is right. When unplugged at J7 it’s easy to turn in both directions, leading me to suspect one MOSFET has failed. Maybe.

Makes sense, I guess next step could be probing the two chips. Probably it’s an H-bridge configuration that’s why it’s using 2 N-channel mosfets and 2 P-channel mosfet, I found the specs:

4951GM dual P-channel mosfet https://datasheetspdf.com/pdf-file/1008247/AdvancedPowerElectronics/AP4951GM-HF/1
9977GM dual N-channel mosfet https://datasheetspdf.com/pdf/1108841/SiliconStandard/SSM9977GM/1

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Thanks. I suppose I could probe the MOSFET inputs and work out which ones have failed and then just replace that one. I can’t find a UK supplier of these particular chips, though…

I’ve tentatively identified the diode-like component behind the motor connector as a TVS diode. Does the fact that the MOSFETs appear to have been damaged mean that the TVS has failed too?

I don’t think so, honestly, go for the mosfet, they are very fragile to forward currents.

Get yourself a flux pen and a desoldering pump , tape the area around the component with paper tape or cheap kapton tape , put some of it on the component and then some new solder on the pins, find something to push the component away while you quickly alternate between both sides with the soldering iron.

Clean the area, apply more flux and put the new component in the right position, you can hold it down and then solder one or two pins to the board and solder the rest of the pins, use a lot of flux, good lights and a lens.

good luck :slight_smile:

and remember, if it doesn’t work, was already broken.

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Considering its an SO-8, an alternative to attempting to desolder the whole thing is just to sacrifice the chips and cut them off at the pins, then remove the pins individually. Clean up pads using solder wick.

Less risk of damaging the PCB if you’re not too experienced in smd soldering.

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The first of the spare MOSFETs have arrived from China (couldn’t find a UK supplier) and I’ve changed the 9977.

I think I did a good job, but it’s still not working. Hopefully changing the other MOSFET will fix it (when it arrives)

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