P750DM and P870DM Troubleshooting

Hi all,

Long time since I've been on the forums - good to see the community is still alive and well.

I have a P750DM and P870DM, both with issues, and I am trying to resurrect at least one of them.

P750DM issues:
Does not boot without wall power connected.
After ~20 seconds, fans ramp to 100% (with or without battery connected) on both CPU and GPU (980m), with a single beep every 3 seconds or so, until the computer shuts off. Can't find beep codes anywhere...
Bios is not factory, but it's been years since I flashed it, and I didn't have issues since then so I don't remember the exact source of the bios that I flashed. It is not a mod - I got it from a reseller if I am remembering correctly.
Can boot into windows, but shuts off right afterwards.

P870DM issues:
Two horizontal lines on the top left of the screen (4k screen, 980 desktop gpu). Lines are not stuck to one color, and only intrude 25-40% (fading to the correct color) from the left edge towards the center. Each line is 1 pixel in width, and the two lines are about 9 or 10 pixels apart (guessing). System otherwise boots fine and thermals are not an issue.
Lots of unknown devices in device manager, no drivers via obsidian utility... not sure where to update drivers (or which drivers are important to update).


The same 6700k and wall power was used to test both systems.

Any thoughts on the issues in play here?

It would be incredibly helpful to be able to salvage one of these systems...

thanks in advance,
bob

 

P750DM sounds like it's overheating - I had the same problem on a similar model, it wasn't recognizing the MXM card's sensor and assuming the worst.

 

+2 rep for temp sensor idea.

Looking at the motherboard schematic, the only thing I can find that might be serviced is "Thermal Sensor RT1" on EC SMBUS, TH05-3H103FR... a thermistor.

If I had the board layout for the V3.1 PCB, that would be easy to check for failure, but it's not immediately obvious where I would find the thermistor. Maybe it's not even the issue... since it's apparently for the CPU, not the GPU.

Do you have an idea where on the 980m pcb I might find the thermal sensor? Are there any schematics floating around for this?

 

Checked RT1 to ground, and I'm getting 5.57kOhm instead of 10kOhm, no parasitic capacitance messing with the measurement. R588 is impossible to find on the board to check, but I'll keep this in mind for later.

Checking R508 and R509 if possible now.

 

Do you have a spare MXM card to test with? You can also read some thermal data in the BIOS.

 

Unfortunately, the p750dm is running a non-Prema potato bios that has zero thermal data.

System also crashes out of bios for what it's worth.

I've checked all of the resistors associated with the VGA thermal alert, overtemp, and SDA/SCL lines, and everything looks okay.

Unfortunately, there isn't a very doable way to check the mosfet functionality for the 3.3v/5v I2C bus conversion needed from the GPU.

However, I shouldn't have too much trouble tapping into the I2C via the speaker amp (which I have windows dev tools for...) and maybe I'll at least be able to see what the thermal data looks like. Gotta figure out the addresses....

At this point, I am beginning to suspect that the person I sold the chassis to may have flashed the EC/Bios incorrectly (not that I know the correct method myself).

 

The important drivers would be Intel chipset and Nvidia display drivers.