Unable to repair damaged PCB on Lenovo T590

[jeffl1980]

Lenovo T590
Model 20N5S0W300
SN PF1BXUWM
Mobo FP531

In a poorly executed attempt to re-program BIOS, I believe I knocked off SMD resistors near the BIOS chip (MACRONIX MX25L25673G) pins 1, 2 and 5. Since the resistors were low values, I attempted to make the repairs using solder blobs. I am inexperienced and the workmanship is admittedly poor. I programmed the BIOS chip with the initial firmware read I performed. In other words, I believe the BIOS firmware currently matches what it was prior to any work I performed.

Here are my current observations.

• Board has power, orange light illuminated
• 3.3V measured at BIOS chip pin 8
• No signs of life when I press power button (power button does not illuminate, nothing on screen, no CPU fan noise)

What are appropriate next steps for troubleshooting?



Additional info that may or may not be relevant -

I opened up this laptop to clear a BIOS password. I misinterpreted the instructions on this forum as referring to CPU gen instead of Thinkpad gen. As a result of my error, I followed the DXE password bypass driver injection instructions and flashed a new BIOS created by the Lenovo Autopatcher python script. As noted above, I believe the original BIOS firmware has been restored to the chip. My goal is restore operation such that I can follow the appropriate BIOS password removal procedure.

[SMDFlea]

Bios requests go here - https://www.badcaps.net/forum/troubl...-requests-only https://www.badcaps.net/forum/troubl...before-posting

[jeffl1980]

Understood. I am not requesting a BIOS firmware. I mentioned the BIOS password for context only. I recognize that I'll have to perform the Lenovo Thinkpad EC password bypass procedure once I restore operation of the laptop.

[reformatt]

Motherboard is NM-B901 BTW. Schematic/boardview are available on the forum. Boardview is Teboview format, you can use Boardviewer (from Boardviewer.net) to view.

Affected area is R2101, R2102, R2104. Seems R2102 is missing? Hard to tell from your photo. Should be a 51 ohm 0201 resistor. Looking at your work, it doesn't look like you are using flux. Installing 0201 components takes a bit of practice and needs the right tools, which I doubt you have. You also need to be extremely careful in this area as these data lines go directly to the CPU. If you aren't taking anti-static precautions, the result could be fatal. Do a diode reading with a meter on this data line first (SPI_MISO_IO1) as you may be wasting your time if you zapped it with ESD.

To sort the physical damage, you will need a hot air station, fine tweezers (I recommend Mechanic KA-11 as these points are very fine and allow you to place components in areas where the components are very close together) and some good flux (Mechanic M35 is quite good and relatively cheap if you don't have access to Amtech etc). 51 ohm 0201 resistor (either order individually or part of a sample book). I can't do this stuff without a microscope either so you might need something in that area too.

BTW, the only clip I recommend for on-board is the Pomona 5250 clip (you can get these off Digikey/Mouser, don't buy off Aliexpress as they will be fake). But your programmer is often loaded down by the board and I usually remove the IC and put directly in a programmer.

[jeffl1980]

reformatt, thank you for taking the time to provide such a detailed answer. I will follow your guidance. The odds of success may be low given my inexperience but I definitely look forward to using this as learning opportunity.