Motor and Driver blown Thrustmaster RGT FF Pro Clutch Edition

Hello fellas,

last year i bought a used Thrustmaster RGT FF Pro Clutch Edition and really fell in love playing Project Cars on my PC with this little piece of technology.
But recently the Force-Feedback motor and driver, which seems to be an H-Bridge as i could find out, blew themselves. Everything is still working fine except the FF. Now i really want to repair it as i cant afford any other hardware at the moment.
Bad thing is that the motor hasnt any data written on it except an RoHS number which doesnt help me at all. I only know that its running on 20V DC. Sounds quite like a permannent magnet universal motor to me.
The IC has at least a sticker underneath the heat sink, but some of the information got lost. All i can read is "L###847" and "#WNG" as you can see in the attached picture. It has 28 pins.

I contacted Thrustmaster but they didnt want to give me any information of course. Also i couldnt find any circuit diagrams on the internet.

Can someone help me finding spare parts to get the FF going again? I can provide additional pictures, if you need them.

Greetings,
monmon


@mods: Since Im new to this forum, I didnt know if this is the right section to post this in. If not, please forgive me and feel free to move it to a proper one.

@monmon
I remember see this chip years ago in an epson inkjet printer.
You are looking at a LB11847 chip
Thrustmaster must be using it as a current/torque controller as it designed functions were for stepper motors.

You got it, mate! Thats the part i've been looking for. Thank you so much!

Sorry for the late reply though, i didn't expect an answer that fast to be honest.

According to the datasheet its max. output current is 1,5A. Thats allright since the original power adaptor, which only powers the FF, provides 20V/0,75A.
So the whole FF system is capable of using 15W. The motor is directly driven by the chip with two 5W resistors connected in row. It is indeed a stepper motor, i can feel the steps when turning its axle with my fingers.

Do i have to look for a stepper with a power consumption of 5W now?
Also it only has two connectors. I have never seen a stepper with less than 4 connectors. May the windings be connected internally?


Greetings,
monmon

@monmon
I have never seen a thrustmaster steering wheel internals but my so called "uneducated" & "inexperienced"guess from the pic you show, I can mostly work out how the wheel functions.

I am 99.99% sure that the motor is a dc permanent magnet brushed motor.
How do you know that both motor & driver are blown?
Have you tested the motor by itself? Disconnect the motor and test with a battery, if it spins smoothly it is probably OK. If it kinda stutters it could be brush wear or the commulator is shorted/clogged with carbon dust. Maybe the bearings/bushings are seized. All these are repairable.

From looking at the board I can work out what TM are doing with the LB11847.
TM is not using the chip as it was designed to do, they are only using half the chip ie. one h-bridge used to drive a bipolar motor. Bipolar is needed as you need to be able to reverse the motor.
If you look at the LB1847 datasheet you will see it is a current controller driver for stepping motors with 16 steps of current output.
TM haven't gone and used the 16 steps but gone for pwm current levels. All 4 Ia input signals are tied high setting it to always 100% output current.
What varies is the Vref which is supplied by a pwm signal from the microcontroller and then goes to a rc filter which gives an analog voltage to Vref.
Vref is the setpoint of current allowed to the h-bridge, it will turn on the fets till it senses that the current level reaches setpoint and then turns off the fet(via a latch). There is also a oscillator which cycles a set/reset latch where current setpoint reached will set the latch and the oscillator will reset the latch at say 15khz. With the latch reset it allows the current through till it reaches setpoint again, this is continuous.
To test the driver I would probe the PWM signal to see if it was present and test the output is working, there is one other signal going to the chip and that would be PHASE1 which controls the direction. If you are confident in soldering and the driver is blown, you could rewire and maybe use the second half of the chip.

Incidentally you could use this chip to directly connect to a mmos controller and have true torque driven wheel(unlike the pwm/speed control when directly connected h-bridge).

@OZHEAT

Not the impression i got of your skills.

I'll add the missing 0.01%. I don't know what made me think this is a stepper. When turning it and holding it to my ear i can clearly hear the brushes. If you look really closely (quite hard to see on the photo), you can see grime between pin 5 and 6 of the LB11847. So my guess is that the motor shortened and blew the driver. Also it really smelled like burned electronics when the FF stopped working.
I will test the motor at work tomorrow, I don't have a fused power supply here in case it is shortened. Measuring its winding resistance between the two connectors gave me every value from zero to endless ohms in irregular steps. Also due to the mechanical irregular "steps" i can feel when turning it something inside the motor can't be good anymore.
I'd rather replace than repair it because motors in that class can't be that expensive, I guess.

Your explanation of the circuit seems to fit perfectly. I will try to test the driver with the TM configuration tool. Maybe you're right and i dont even need a new LB11847 when using the B outlets.

greetings,
monmon

Hey @monmon - in that picture, did you already remove a heat sink before you took it? Just curious because it looks like it should have one. Since you mention buying it used is why I ask.

@Zed
There was a heatsink mounted to the chip, i just removed it to check its number and take the picture. I am also the first one that opened the case of the wheel.

I am confused right now. Tried the motor on a power supply today and it ran smoothly. Its power consumption was ok as far as i can judge. Not over 50mA without load @20V. With load (held the axl with my fingers) it raised almost linear.
Is it possible that only the driver burned to whatever reasons?

greetings, monmon

@monmon - it’s hard to diagnose from a distance but a number of things can lead to chips burning. Since the motor seems ok, it could have just been a strong static shock somewhere along the line that set it up for failing. Maybe it got really hot somewhere along the line before you got it, or maybe it was just a weak part from the start and had a defect. But hard to say. I’d just swap the part and see how things go.

Good luck!

@OZHEAT
I did some measurement today and thats the results:
Vref1 doesnt vary, it's constantly 1,56V (DC).
OutA+, OutA-=0
Vref2=0
Enable1=0
Phase1=0-5V, With no FF forces applied it's 2,5V
Enable2=5V
All Signals are V DC.

With Vref1 I'm not completely sure if there isn't an AC signal. When trying to measure it, the TM driver on my PC crashed. Maybe because my Multimeter pulled the signal to GND a bit. Unfortunately i don't have an Oscilloscope here to confirm. There is a signal, so the chip should have output signals. But the two Out A ports are definitely dead.

So if I get this right there are two possibilities now. Rewire or replace. I found an offer on aliexpress where there is 5 drivers for 1$ each in a package. Guess I'll try that.


@Zed
Thanks, I'll go for replacement.


btw: Why are you using the tagging function with @ all the time? To notify each other?

@monmon
Sorry for the late reply
vref1 sitting at 1.56v is either going to be stationary or perhaps the startup calibration routine.
Vref1 is the current limit, when reached will shutdown the mosfet till next cycle begins
phase1 is either going to be 0v or 5v depending on direction.

If it was me, l would just use the other half of the lb11847 driver but this does involve some skill to lift some pins and reroute with wire.
Easiest way would be to purchase a new lb11847 (btw the same chip is also known as lb1847) and it would be an easy remove & replace.
Might be worth looking at the electronics shops in your country such as rs parts, farnells digikey etc as you only need a single chip, the wait for china sourced parts is a killer.

Anyway good luck with whichever way you choose.

ps yes the @ in front of the user name, tags it so it notifies the user to the post.

@OZHEAT
I ordered a lot of lb11847 on aliexpress to replace it. Had to go for the cheap option because I'm short on money (student problems, hah? ).
But I don't have the time anyway to rewire at the moment, so I don't really mind waiting.
For Germany I could only find them at Farnell and UK ebay sellers, but there is the money problem again.
I will report results when I replaced the driver.

Thanks a lot and for your help guys!!

@OZHEAT
Finally the drivers from China arrived and I have already replaced it.
The wheel works like on its first day again, the motor was indeed okay. Unfortunately some pads on the PCB won't survive another repair. They came off quite fast during the soldering although I was very careful. So lets hope the driver won't brake again in the near future.

Thanks again for your help guys!

@monmon
Good to hear it is working again.
congrats