Hi guys,
This is my first post! 🚀
I have no idea what I’m doing, but I’m learning by trial and error.
I’m currently working on a Dell Optiplex AIO 7490—one of a bunch of AIOs that mysteriously failed to POST just a few days after the warranty expired. The original issue was that the PC worked fine until it was rebooted, after which it got stuck on a black screen (no backlight), with fans spinning at normal speed and a solid white power LED. Forcing it off by holding the power button would just cause it to switch on automatically and get stuck again on the black screen.
I found that replacing the CMOS battery and waiting a few minutes would allow the system to POST and start normally. However, once shut down or restarted, it would get stuck again with the same symptoms—black screen and solid white LED.
I tried updating the BIOS using the official methods: via Windows, a WinPE USB drive, and directly from the F12 BIOS menu. It loads the firmware and appears to process it, but after restarting, it doesn’t proceed with the flashing.
So I decided to try a chip-off flash. Using my super cheap rework station, I removed the XMC 25RH256CKIQ (SOP16), backed it up successfully with my very cheap CH341a, downloaded the BIOS from Dell’s website, and extracted it using the PFS Python script (which I’m sure many of you are familiar with—it’s basically the only way to extract these newer Dell BIOS packages!). I edited the dump by replacing the BIOS section with the content of the System BIOS file from the new package, flashed it, and re-soldered the chip onto the motherboard.
Now, when I press the power button, I get a red power LED—only while pressing it. Nothing starts. I reflashed the original dump (verified multiple times), but it still only shows the red LED on press.
I’ve tested all the small components around the BIOS chip for possible damage from the rework station—they seem fine. I also checked all the pins for continuity, and they’re good. The power supply voltages are fine (compared to a working unit), and the BIOS chip is getting 3.3V. The only thing I noticed is that the chipset under the motherboard gets slightly warm when the power cable is connected.
Any suggestions on what to test next? I’m determined to fix this, but I need a little help figuring out the next steps. Any info would be greatly appreciated!
This is my first post! 🚀
I have no idea what I’m doing, but I’m learning by trial and error.
I’m currently working on a Dell Optiplex AIO 7490—one of a bunch of AIOs that mysteriously failed to POST just a few days after the warranty expired. The original issue was that the PC worked fine until it was rebooted, after which it got stuck on a black screen (no backlight), with fans spinning at normal speed and a solid white power LED. Forcing it off by holding the power button would just cause it to switch on automatically and get stuck again on the black screen.
I found that replacing the CMOS battery and waiting a few minutes would allow the system to POST and start normally. However, once shut down or restarted, it would get stuck again with the same symptoms—black screen and solid white LED.
I tried updating the BIOS using the official methods: via Windows, a WinPE USB drive, and directly from the F12 BIOS menu. It loads the firmware and appears to process it, but after restarting, it doesn’t proceed with the flashing.
So I decided to try a chip-off flash. Using my super cheap rework station, I removed the XMC 25RH256CKIQ (SOP16), backed it up successfully with my very cheap CH341a, downloaded the BIOS from Dell’s website, and extracted it using the PFS Python script (which I’m sure many of you are familiar with—it’s basically the only way to extract these newer Dell BIOS packages!). I edited the dump by replacing the BIOS section with the content of the System BIOS file from the new package, flashed it, and re-soldered the chip onto the motherboard.
Now, when I press the power button, I get a red power LED—only while pressing it. Nothing starts. I reflashed the original dump (verified multiple times), but it still only shows the red LED on press.
I’ve tested all the small components around the BIOS chip for possible damage from the rework station—they seem fine. I also checked all the pins for continuity, and they’re good. The power supply voltages are fine (compared to a working unit), and the BIOS chip is getting 3.3V. The only thing I noticed is that the chipset under the motherboard gets slightly warm when the power cable is connected.
Any suggestions on what to test next? I’m determined to fix this, but I need a little help figuring out the next steps. Any info would be greatly appreciated!
