Dell M4800 - Track Point Not Working?

Issue might be that the connection between the keyboard and motherboard isn't working properly, and if the system can't find the trackpoint, it will also disable the top buttons, or other way round?

Did you try checking the cable connections on the USH board? I believe there are 4 cables coming from that (including the touchpad). I'm not sure where it's mounted on the M4800, but on my M6700, it's mounted under the palmrest, I have pictures of the USH board it in the M6700 owner's thread:
http://forum.notebookreview.com/del...sion-m6700-owners-thread-272.html#post9800330

 

Not sure what USH board exactly is, but there is a very small board like that on M4800 connects express card slot into the IO board. The ribbon cable out of the 3 buttons connect into the touchpad (under) and touchpad will connect to the IO board, which is in return connected to the motherboard via a hard plastic bracket, not a ribbon cable. And there is no other board board on the palmrest besides the touchpad.

Regards to keyboard ribbon cable, I literally quadruple checked under the keyboard, etc. Physically everything is perfect..

Thanks again for the ideas!

 

That’s how I understand it too. Precisely as it is extremely unlikely that two separate failures occurred at the same time, affecting both the trackpoint and its buttons, is it likely that one single fault somewhere tricks the computer into not recognizing both parts.

It is a situation likely unforeseen in the computer’s design; perhaps if something doesn’t find the buttons it stops looking for the trackpoint, or the other way around, or something similar.

Now what are the possible points of failure? I see four major: the touchpad board, the keyboard assembly, the I/O board, and the mainboard.

Apparently, there is quite some logic of its own in the touchpad board, as it controls how the button clicks are interpreted. There could be a bit of logic in the keyboard assembly, adjusting trackpoint sensitivity and such, and both parts probably have to communicate with each other through somewhere, but it is open for debate what and where controls both of them and makes them appear as one device.

My take is that it is quite unlikely that any such ‘control chip’ would be placed on the mainboard, as it would unnecessarily add another point of failure to a rather costly part (I assume), with a rather high work-cost of replacement.
The only thing on the mainboard that should have anything to do with these built-in pointing devices should be the QM87 chip itself (its integrated LPC controller).

If you are desperate to repair your computer, I suggest you try to get hold of another touchpad assembly and try to replace that, and if it doesn’t work, then try replacing the keyboard. Only then would I try the I/O board and the mainboard.

I haven’t really looked how much what costs. Hopefully, once you get your trackpoint working again, you might sell the surplus parts, except the one found faulty, of course.

Maybe it would be practical to walk up to some Dell service center, if there are such shops in your area, have them try this, and be ready to pay for whatever part will solve the problem. Of course, I cannot know if this is an option for you…

 

Great recommendation and logical deduction MJS! These are what I tried and what I think. (New lead as well).

1. I tried swapping the keyboard with that of M4600. M4600's ribbon cable was not making keyboard be recognized, so I had to swap and use M4800's keyboard ribbon cable to test it. And there is a small PCB board with a few chips that I think definitely is related with regulating and controlling trackpoint. When I swapped with M4600, I double checked that ribbon cable was perfect and etc. With M4600 keyboard, exact same issue. Keyboard works fine, but not trackpoint. Does not get recognized on the Touchpad settings on Windows for the trackpoint (same issue as M4800's keyboard).

2. The top 3 buttons designated for the trackpoint WORK ON BIOS. With M4800 original keyboard, it now WORK ON BIOS. (So my previous reply saying it didn't, I am not sure what changed. My memory is now going blurry..) Trackpoint nipple itself however does not work on bios. These 3 buttons still do not work if I boot to Windows. But the left click (only click anyways that bio can recognize) works so I can rule out bad connection of buttons into touchpad board and touchpad board into IO board. I think the entire IO board and palmrest assembly (Touchpad) at this point is green light because at least it works electronically.

3. With the keyboard from M4600 not working, I must say I am afraid it may be the motherboard? Keyboard is connected straight to the motherboard, unlike the touchpad (into IO board). Right where keyboard is connected, I think there is a chip on motherboard that regulates keyboard/trackpoint (Speculation, but looks similar to the one in keyboard's own PBC board).


With M4600's keyboard also having issue being recognized in settings as well and 3 buttons work on BIOS, I can:

1. Rule out Keyboard as failure.
2. Rule out bad touchpad/palmrest assembly including ribbon cables
3. Rule out bad IO board (Does its job connecting 3 buttons for the trackpoint and have it work on bios, at least electronically)

Only thing I could not rule out technically was the motherboard. Oh boy..

I really appreciated your feedback. Is there something you think I can now try with these new leads? (Besides getting a new mobo haha..)

Thanks again guys I super appreciate all replies. It's gotten real progression haha..

 

Before implicating the motherboard, you can yet focus on the keyboard cable one more time. It’s the one part you had to use with both keyboards. I know you wrote many times that you checked all cables. No offense, I wonder if that only means inspecting that they look okay. At this point, you might get a hold of an instrument that can measure and prove that all wires in the cable can actually lead current without any loss, especially when you fold the cable as it is folded inside the computer. (Or try another cable for M4800?)

I hope this helps.

 

MJS, thank you again for the quick reply.

Funny thing is.. keyboard cable on M4600 and M4800 should be the same. They look same and M4800's work on M4600.. So why cant I use M4600's cable on my M4800?

Actually this is what I should try to figure out...

 

This is a tough one.

By the way, did your M4800 keyboard work on the M4600 including the trackpoint?

 

Here’s a thought…

There are two cables. Apparently identical. A keyboard works with one of them but without its trackpoint. The same keyboard does not work with the other cable at all.
This makes me believe there is a ‘marginal state’ somewhere. Over the newer cable, the keyboard still works, albeit without the trackpoint, while over the older cable, nothing works.

Where’s the marginal state and what is it?

What if the cause of the problem were the very power supply into the keyboard assembly? The keyboard and the trackpoint need some amount of power to work—not very much, I’d say, but what if they would get less than needed? Could it be that the keyboard might still work but the trackpoint would not?

It would still point to the motherboard, by the way. Even if it were some marginal failure in the connector or something similarly stupidly simple somewhere nearby.

 

MJS. Thank you 1000% again for this.

It really looks like cable for keyboard for M4600 and M4800 are different. There is 0 vs.1 revision on their part number (Diff part number). Does not work if I swap for both machines.

I confirmed that my M4800 keyboard trackpoint works on M4600. So keyboard was not issue.

When I hooked up M4600's keyboard that fully works, I still got no trackpoint settings under M4800.

Without trackpoint SETTINGS in the first place, I feel like something is wrong with some kind of a controller chip on the motherboard.

This is what I have so far:

1. Two ribbon cables are different
2. Keyboard works
3. Palmrest buttons work

So yeah.. looks like motherboard at this point..

Now that I really narrowed this down, would there be ANYTHING else I can try? Like resetting, some kind of deeper than bios settings?

Thanks again fellas!

 

I am not yet sure if the M4800 ribbon cable can be greenlighted.

Can you please clarify how both cables behaved when you tried your M4800 keyboard on M4600?
Do I understand you correctly that you had to hook up the M4800 keyboard through the M4600 ribbon cable for the keyboard to work on M4600?
This would still leave the M4800 cable unconfirmed to not be the cause of everything.

If that’s the case, I think you might still want to check the cable electrically—before thinking about motherboard replacement.