Thinkpads Forum

Today I used my P51s and after half an hour I pressed the start button to wake it up - nothing happened except from getting in to a loop; the start button and keyboard lit up, then went out, after a while it lit up again - just over and over.
I have encountered similar problems om other Thinkpads and have solved it quickly with the discharge trick - press the power button for 30 seconds and also pressing it repeatedly. Googled and many suggested to remove the CMOS battery but also the internal battery and RAM sticks. Didn't help.

I removed RAM's, one at a time and could get it to start. After trying different combinations I came to the conclusion one RAM slot is defective. I have never opened up it previously so it couldn't be caused by physical damage.

So any suggestions? Is it doomed to be scrap?

Have you actually run a memory test like memtest86+? IMO one of the RAM sticks going bad is more likely.

No, I mentioned I tried different combinations - and both memories work in one slot but not in the other.

Looked for bad solderings under a microscope and cleaned contacts with isopropyl alcohol. So it's gone....

axur-delmeria wrote: ↑

Tue Apr 15, 2025 8:40 am

Have you actually run a memory test like memtest86+? IMO one of the RAM sticks going bad is more likely.

IMHO you're skipping steps and jumping to the "bad RAM slot" conclusion. I'm not saying that the RAM slot is OK, but it's better to be thorough.

Only after completing a few passes of memtest86+ on each RAM stick (only 1 stick installed at any given time), and confirming that both are good, can we start exploring other possible causes.

Yes, of course I would prefer to do a memtest but it doesn't boot with a RAM in place in the bad slot. So I can start a memtest with a RAM in the working slot but...

I don't know about the P51s but on my P52 there's a hardware test and then it perhaps will tell if there's something wrong with the motherboard.

axur-delmeria wrote: ↑

Tue Apr 15, 2025 9:51 am

IMHO you're skipping steps and jumping to the "bad RAM slot" conclusion. I'm not saying that the RAM slot is OK, but it's better to be thorough.

Only after completing a few passes of memtest86+ on each RAM stick (only 1 stick installed at any given time), and confirming that both are good, can we start exploring other possible causes.

dynaflux wrote: ↑

Tue Apr 15, 2025 10:27 am

Yes, of course I would prefer to do a memtest but it doesn't boot with a RAM in place in the bad slot. So I can start a memtest with a RAM in the working slot but...

I wrote only 1 stick installed at any given time). This means

1. Install RAM stick #1 on the "good RAM slot"

2. Run memtest86+ to test if it's good. Complete maybe 3 passes.

3. Turn off laptop, disconnect charger and battery, remove RAM stick #1, install RAM stick #2 on "good RAM slot"

4. Rum memtest86+ again, Finish 3 passes.

5. Now, if both RAM sticks pass, then we start considering other possible causes, the bad RAM slot included.
If one or both RAM sticks fail, well.... there's your problem.

Simply put, RAM stick failure is much more common than the slot itself malfunctioning, that's why we should eliminate that one first before investigating more exotic failure modes.

What is Memtest86+? From its website: https://memtest.org/

Memtest86+ is a stand-alone memory tester for x86 and x86-64 architecture computers. It provides a more thorough memory check than that provided by BIOS memory tests. Memtest86+ can be loaded and run either directly by a PC BIOS (legacy or UEFI) or via an intermediate bootloader that supports the Linux 16-bit, 32-bit, 64-bit, or EFI handover boot protocol. It should work on any Pentium class or later 32-bit or 64-bit x86 CPU.

Download the USB installer on their website, grab an empty USB flash disk and run the installer.
NOTE it will erase the contents of the USB flash disk, so if it contains any files, back them up first.
Memtest86+ is small, only a few megabytes, so even an ancient 256MB USB flash drive is OK.

Configure the BIOS/UEFI to boot from that USB drive, and it will start automatically.