Hello everyone.
I have come here with a rather specific question. I was given a Dell Latitude 7420 laptop with a busted screen, and wanted to see if I could refurbish it into my daily driver. I wanted to experiment and see if a 2-in-1 display would work as the chassis of the laptop and 2-in-1 7420 looked identical. I threw in the display and my hypothesis was correct, however, I was greeted with a locked BIOS and since I didn't know the password, I figured I'd try to unlock it somehow. I bought one of those POGO pin probe things for my CH341A programmer so I could read and make a backup from what I'm pretty certain was the BIOS chip. I backed up the BIOS and saved it somewhere safe.
Here's where I think I began to make mistakes. I had the idea that the POGO probe was supposed to stay in place when pressed down, because it technically did the first time I did a read of the BIOS. I tried making it stay on the BIOS chip after I took it off, and kept trying and trying but I thought I was doing something wrong. Turns out I'm just supposed to hold the thing in place by hand. I thought it was a great idea to bring my soldering iron to the chip and just reflow the solder joints as I had poked the crap out of them. I did so and I believe I damaged a neighboring surface-mount capacitor. After I was done with the iron, I went back to the programmer. I used NeoProgrammer and selected the W25Q256BV as my 25R256JVEN wasn't listed. I did a dump of my BIOS and I found an unlock script from another member here and gave it a try with my dump file. It seemed to work fine (my dump was originally 32MB), so I flashed the modified .bin file to my Latitude.
It turned on, CPU and SSD got warm, but the system kept bootlooping and the fan ramped up to maximum speed. I was pretty bummed, so I tried another BIOS image that was cleaned on a different thread, and still no avail. I tried messing with my iron to see if reflowing the chip would do anything, but that seemed to make things worse again, as the system would turn on with the keyboard illuminated, then turn off. At this point I just flashed the original dump to eliminate any extra variables.
I took it into my job the next day to play around with the microscope and see if there was anything visually wrong. I really didn't see anything out of the ordinary, the only thing is, I sort of ate some of the chip off with the probe I was using, so in the pictures you'll see, some of the chip looks rough. At any rate, I got some fresh solder onto the joints, and made sure there was no bridging. For some reason I got bored and thought it would be a good idea to try and desolder the chip entirely and visually inspect it, but that was the final nail in the coffin. As of now, the power button only lights up, and when I press it, I do observe that some voltage comes out of the USB ports, but otherwise, nothing else happens.
Basically, I know very well that I probably shouldn't have touched anything with a heat gun, let alone soldering iron, but in my defense normally this wouldn't have caused any kind of issue. I'm almost positive my issues lie with the BIOS chip and/or the SMD I knocked up. The traces are maybe a little scuffed up, but I've never casually messed up a trace so I'm sure that aspect of the board is fine. It kinda looks like I have a glob of solder on that SMD, but a second eye would be nice as I don't know for sure. The idea I had would be to just buy the exact same flash chip, desolder the old chip and solder the new one, and program it with my backup.
I'm trying to avoid buying a new board entirely, so any insight as to what I should do would be greatly appreciated!
Thanks in advance!
I have come here with a rather specific question. I was given a Dell Latitude 7420 laptop with a busted screen, and wanted to see if I could refurbish it into my daily driver. I wanted to experiment and see if a 2-in-1 display would work as the chassis of the laptop and 2-in-1 7420 looked identical. I threw in the display and my hypothesis was correct, however, I was greeted with a locked BIOS and since I didn't know the password, I figured I'd try to unlock it somehow. I bought one of those POGO pin probe things for my CH341A programmer so I could read and make a backup from what I'm pretty certain was the BIOS chip. I backed up the BIOS and saved it somewhere safe.
Here's where I think I began to make mistakes. I had the idea that the POGO probe was supposed to stay in place when pressed down, because it technically did the first time I did a read of the BIOS. I tried making it stay on the BIOS chip after I took it off, and kept trying and trying but I thought I was doing something wrong. Turns out I'm just supposed to hold the thing in place by hand. I thought it was a great idea to bring my soldering iron to the chip and just reflow the solder joints as I had poked the crap out of them. I did so and I believe I damaged a neighboring surface-mount capacitor. After I was done with the iron, I went back to the programmer. I used NeoProgrammer and selected the W25Q256BV as my 25R256JVEN wasn't listed. I did a dump of my BIOS and I found an unlock script from another member here and gave it a try with my dump file. It seemed to work fine (my dump was originally 32MB), so I flashed the modified .bin file to my Latitude.
It turned on, CPU and SSD got warm, but the system kept bootlooping and the fan ramped up to maximum speed. I was pretty bummed, so I tried another BIOS image that was cleaned on a different thread, and still no avail. I tried messing with my iron to see if reflowing the chip would do anything, but that seemed to make things worse again, as the system would turn on with the keyboard illuminated, then turn off. At this point I just flashed the original dump to eliminate any extra variables.
I took it into my job the next day to play around with the microscope and see if there was anything visually wrong. I really didn't see anything out of the ordinary, the only thing is, I sort of ate some of the chip off with the probe I was using, so in the pictures you'll see, some of the chip looks rough. At any rate, I got some fresh solder onto the joints, and made sure there was no bridging. For some reason I got bored and thought it would be a good idea to try and desolder the chip entirely and visually inspect it, but that was the final nail in the coffin. As of now, the power button only lights up, and when I press it, I do observe that some voltage comes out of the USB ports, but otherwise, nothing else happens.
Basically, I know very well that I probably shouldn't have touched anything with a heat gun, let alone soldering iron, but in my defense normally this wouldn't have caused any kind of issue. I'm almost positive my issues lie with the BIOS chip and/or the SMD I knocked up. The traces are maybe a little scuffed up, but I've never casually messed up a trace so I'm sure that aspect of the board is fine. It kinda looks like I have a glob of solder on that SMD, but a second eye would be nice as I don't know for sure. The idea I had would be to just buy the exact same flash chip, desolder the old chip and solder the new one, and program it with my backup.
I'm trying to avoid buying a new board entirely, so any insight as to what I should do would be greatly appreciated!
Thanks in advance!
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