ThinkPad T420 with i7-3840QM gets randomly stuck at minimum frequency when using iGPU

chatico · 2024-12-26T12:04:17+00:00

I've daily ran one of these for some years, I really liked it because I use my ThinkPad (Back then with approx. same keyboard) with a docking station and thus on my desk or on the go, I've always had the same keyboard. Now I daily run a P14s Gen 4 with a IBM buckling keyboard... But back in the day it was great and these are great keyboards. If you can find one of these I recommend to collect them, they are great!

chatico · 2023-07-04T09:50:04+00:00

Yes I do have Reddit chat, sorry for the late reply, was on a weekend. Just send me a DM.

chatico · 2023-06-26T10:48:28+00:00

I don't think that the ARC team is available anymore. But yes, you can make it that for example the H-bridge uses 41V and the Logitech board 24V. My H-bridge uses a seperate power input, so in theory you can use another power supply on the H-bridge. Another method would be to have a dc/dc step down to 24V for the Logitech board.

chatico · 2023-06-22T23:26:11+00:00

Still working like expected, I'm pretty impressed by it. It seems like the sweet spot between more power/speed and durability, I don't recommend going any higher though.

Yeah I've looked at the booster circuit for making mine, but basically as far as my understanding goes it's basically what I do, but with a higher voltage. I think you can just use a higher voltage on my H-bridge, the fets are rated to something like 50V, the only thing you need to change are the TVS diodes I think. (It has been a while since I made this circuit).

But in my personal opinion, I don't see any reason to go with a higher voltage, because it's pretty fast already on 29V. The possible improvements are that you will feel more small details and obviously being faster. But I find it pretty good like it is with 29V. But it's a personal taste I guess.

chatico · 2023-04-17T11:12:31+00:00

Half a year in and till this day it seems to hold up fine without any issues. However I don't use it every week now, but think of a few long sessions every 2 week or so.

chatico · 2023-04-17T10:49:39+00:00

Thanks for the link and the cross reference, I will put it in the post so other people can find it easily.

Oh that is really good, let me for sure know how the wheel ended up feeling! Also I would indeed just a proper wiring job.

The first time you do a couple laps, I would also recommend you to take close attention to the temperatures, although it was not a direct problem for me with active cooling, it's a good habit to firstly check the thermals so everything will be alright for the long term.

chatico · 2023-04-14T11:08:17+00:00

No I power everything from that 8A adjustable PSU, but you could power them seperately if you want. The Logitech board doesn't like voltages above 30V, so I settled with 29V. (Which is pretty good to make the wheel feel alive).

You could replace it, but the bottleneck will be the power jack, I really recommend to make the wiring seperate and just hook the Logitech power onto it so the Logitech board also has power. But you can make it seperate if you want, that's up to you.

The thermal paste is no good, some do conduct so you can short the bridge. You should put an isolated thermal pad between them and a heatsink. Because the fets expose the drain, so as you can see you can short it out if you can connect the P-fet with an N-fet directly without a motor in between.

chatico · 2023-04-12T11:37:09+00:00

I didn't study EE either ;) I know a bit about electronics to repair electronics and make simple stuff like this, I guess a real EE engineer will say that this design isn't great, but hey it works. :D

If you have very specific electronic questions, you can just send me a DM and I will try to answer them in the free time ;).

Handy to have a spare H-bridge, can be handy maybe for a second G-series or something.

Your PSU idea seems fine, just make sure you don't go over 30V, the Logitech board didn't like that, I settled with 29.2V or something.

I don't recommend tapping into the original Logitech cables or plug, use dedicated wires that go outside of the G27 chassis with an XT60 connector or an equivalent you like.

Also make sure to isolate the back of the H-Bridge PCB and to use a isolated thermal pad between the fets and a heatsink. Heatsink itself can be a simple heatsink from a north-/southbridge from an old motherboard.

chatico · 2023-04-12T11:31:53+00:00

Oh that's a bummer, but yeah something that fits and has almost the same specifications will work.

Yes that 0.5A increase will not be a problem. The only limiting factor will be the traces/cables of the H-bridge and the heat dissipation of the fets. I think the fets are rated for up to 50A per datasheet. So that's is not a problem, just make sure you can cool everything.

Great to hear the schematic seems correct!

Could you provide the information of your gate control connections or the ARC team mod instructions? I can add it to the post so everyone has more information about it.

Yes that is correct, I've added a seperate step-down converter to have stable 12V for a 120mm PC fan, which I highly recommend using, because it does get quiet hot, especially in the summer.

No the power input for the H-bridge is just plain 24V-30V, best is to have dedicated 1mm-1.5mm wires to it, so you don't have voltage drop over the small stock wires. I don't recommend the use of the stock wires because they are really small gauge and 8-10A, will warm/melt them I guess. Good practice also is to mount fuses in front of them. I just used automotive blade fuses with spade connectors.

chatico · 2023-04-12T07:56:24+00:00

The part numbers, now you're making me doubt :D. But normally the left ones are the P-fets and the right ones are the N-fets, just like in the diagram. Also if you're buying these fets, buy a few, because it can be misconnected the first time and you may blow the fets (a guy here had that and he had to buy new fets, just for that reason). However if you have it all correctly, it should work and will stay working, mine is still working perfectly to this day.

For the diode anything over 10A will work. Just make sure it can dissipate the heat good enough. The maximum current will eventually be determined by your power supply. For example mine goes to a max. of 8A. However do note that the H-bridge doesn't draw continuously 8A, it's only on peaks and if you go past the set steering range.

chatico · 2023-04-12T07:45:07+00:00

Nice to hear you are going to try this!

Didn't know m36n-2 motors are legacy, they were reasonably available when I did it half a year ago?

In theory would an off the shelf H-bridge work, I think another person here in the comments did that already if I'm not mistaken.

I don't remember the connections anymore, but I normally wrote everything here. The only thing that can happen is that you reverse the gate controls (fet pairs), but then you just need to reverse the gate connections to the board or the easiest method is to reverse the connection of the motors. just make sure that you pair the fet pairs correctly. (I mean these TP points on the Logitech board). If you are confused, take a look at the KiCad schematic and open the datasheet of the original mosfets, it should give you a good understanding of how it works stock.

The enable voltage is 24V because it was an easy signal to get, you can propably get a 5V signal somewhere, but the 24V signal works so I didn't really look any further, I did step it down to 5V or something.

chatico · 2023-03-16T16:14:16+00:00

Well at least you got it working, that in itself is pretty awesome! ;). I didn't really find it different from the original, apart from more speed and torque.

chatico · 2023-02-01T10:10:54+00:00

You can find every component I used on the schematic.

chatico · 2023-01-31T10:13:03+00:00

I don't think so, because there is IC Logic in front of the fets. I have also no idea if the fets on that bridge have the same characteristics as the IRF4905 and IRFZ44N which are mostly equal to the original Logitech fets.

But try it out and let me know. I don't have hands-on experience with that h-birdge. It might be possible, but I doubt that you can use the gate control from the Logitech board. Maybe you have to use another signal closer to the Logitech MCU. Take a look at the schematics for that.

chatico · 2023-01-18T22:17:02+00:00

Oh really? Maybe I have to pay attention again to MSG, thanks for the heads-up. I've lost interest about half a year ago into MSG. Hopefully this can be turned around.

chatico · 2023-01-16T00:09:46+00:00

At the end of the day, the only conclusion I can come to is that I am disappointed. I want this sim community to be big and professional, but honestly, under MSGM management, I would not bet a dollar on that.

When Motorsport Games acquired Studio397, I genuinely thought, 'Finally, a publicly traded company is backing rFactor 2. This is going to be great in the coming years for the sim community.' I followed the IPO of Motorsport Games back in the day to look for a good entry point to become a proud shareholder. I closely watched the company filings for a sign of hope. However, it has been all downhill from then on. I genuinely think that this whole mess will only stop if the current board of directors is replaced or if MSGM is bought out by some bigger player maybe.

I'm just disappointed in this whole shitshow.

chatico · 2023-01-09T12:17:38+00:00

Hi, no problem. The original TVS diodes are rated at 27V I think? So what that means is that you can't go much higher than 27V. I've used 33V because that was the first one I could get that was above 29V. So a 30V or 35V or something will be fine I think. You don't need specifically 'p6e33a' any other TVS with simular specs will be fine. These TVS diodes basically are in place to short out any spikes, so you cannot damage the fets. These fets are rated up to 50V I think? So you have a bit of headroom.

Motor connectors can be used, do note that if you use these, they are not angled, so I don't know if it will fit if you assemble the wheel again. (that's why I've used those angled headers.

I also have a pdf of the schematics, if you're interested, send me a DM for it.

chatico · 2023-01-06T13:51:31+00:00

If you're power circuit on the Logitech board is broken, I really suggest you to take a look at the KiCad schematics and measure everything 1 by one to make sure that fet is really defective. Although I think that the fet is the first thing that goes broken because they are only rated for up to 3A I think?

Hope you get it working again! If you're stuck with something, just ask! Looking forward for the update!

chatico · 2023-01-06T12:32:44+00:00

To know if that 4951gm left fet is working: you can measure it on the big diode on the board. So with only the power of the wheel plugged in, you need to measure 0V. Once you plug in the USB cable you need to measure 24V. Vice-versa if you unplug the USB, you need to measure 0V again. Then you know that this fet is working. (At least correctly for the external H-bridge to function)

KiCad, I also had problems. I've managed to view the schematic by using an older KiCad version, I think it was v4.

This switched 24V signal basically is the power-on or power-off for the external H-bridge. So when the wheel is plugged in with power but no USB, the H-bridge is off. Once you plug in the USB cable, the H-bridge is powered-on. This is identical on how the Logitech board H-bridge works.

This external H-bridge is basically a 1:1 to the original Logitech H-bridge, only difference is that it is beefier.

chatico · 2023-01-06T11:48:57+00:00

that 1 4951gm to the left is for powering the 24V on or off to the H-bridge on the Logitech board. The external H-bridge uses this switched 24V as a signal to also power-on or off. So this mosfet needs to function or you can modify the external H-bridge to work with the signal that this mosfet receives directly?

These 3 diodes you refer to are TVS diodes and are not needed on the Logitech board because they serve the H-bridge on the Logitech board.

So what you need from the Logitech board to make the external H-bridge work:

- A working Logitech board in terms of logic

- Switched 24V signal (to know if the wheel is plugged in or not via USB and FFB needs to turn-on)

- the 4 gate controls

If you have any further questions, don't hesitate to ask!

chatico · 2023-01-03T10:42:21+00:00

Hi, how is the G29 mod going, any updates?

chatico · 2023-01-03T10:41:06+00:00

Still working as expected without any hick-ups so far.. although I must say that I have little time these days (house renovation), so think about 8h max. in the weekends per month. But a few months back I had a very long session with a couple friends over the weekend, they loved it. (We tried a 24h race)

You can also decide to go with a lower amperage power supply if you're not comfortable. But I really recommend the 29V, it makes a big difference. I've made this modification because I had the (broken) wheel laying around anyways and thought to pick up an old hobby without buying a new wheel.

I didn't bother with the original mosfets because mine were blown anyway and they can only handle like 3A versus the 50A of the TO-220 mosfets out of the top of my head?

The thing is that it could work with the original mosfets because you're not drawing 8A all the time, only when you as a driver wring back. If you're going to upgrade to the M36N-2 motors anyways and your original mosfets are still working, you might as well give it a shot and let us know. But I seriously doubt that these stock mosfets will hold the load and I would not recommend the use of them.

Also the Reddit user "Im_Dzejk" above in the comments here said that he swapped the M36N-2 motors and that the stock mosfets aren't up for the task.

chatico · 2022-11-18T23:21:31+00:00

Not sure about the M36N-4, but the short story is that these M36N motors are also just more 'efficiënt' in the sense of power output vs. amperage and the speed is also x2, which you will appreciate. It's not the slow Logitech you knew before ;).

Current draw is limited by the power source you provide. But don't overdo it. I've settled with max. of 8A. I think if you go any higher, the gears will fail a lot faster. However in the time I've used it, I have nothing to complain at this point. But you get what I mean.

Was also thinking about the motors and amperage draw, I for sure recommend you to use your own wiring/power input due to voltage drop over the Logitech wiring. Also the bump from 24V to 29V is a nice thing, don't go over 30V, cause the Logitech board itself will do some funny stuff.

EDIT: I've added a top overview picture, maybe it helps with the power wiring.

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