CPU Bypass capacitors knocked over

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Lenovo Legion 5 15ACH6H

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Tushie @tushie

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Postado: 14 de out de 2023

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CPU Bypass capacitors knocked over

Whilst replacing my thermal paste, I accidentally knocked over (and lost) 3 bypass capacitors, the pads are still in place (thankfully) how difficult are they to replace and what is the name of the component?

I’m debating whether or not to replace them myself or let a technician do it if it’s not prohibitively expensive and how safe it is to temporarily use the laptop without replacing them

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Chris Green @chrisgreen

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Postado: 15 de out de 2023

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You won't find these capacitors in the schematic for the laptop / its motherboard because they are part of the CPU package. These capacitors are there to provide filtering for the power going into the CPU die, and generally that power needs to be very "clean". However, I'm not fully convinced you knocked them off unless you were really rough cleaning the old paste. Like Bill mentioned, they could be unpopulated from the factory.

There's relatively low risk to testing out the laptop in its current state, it may not want to boot up, but you won't do any long term damage to the machine / its CPU if those capacitors are actually necessary.

Also, this may not be the same exact CPU, but note that some capacitors are missing in this similar AMD SoC:

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Yes, seeing some teardowns , the CPU has caps missing in the exact spots as me as seen in the updated pictures!

15 de out de 2023 por Tushie

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Yes, seeing some teardowns , the CPU has caps missing in the exact spots as me as seen in the updated pictures! — Tushie

jayeff @jayeff Rep: 449,3 mil 11 366 1,4 mil · Answer 1 · 2023-10-14T23:51:15-07:00

jayeff @jayeff

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Postado: 14 de out de 2023

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Hi @tushie

Manufacturers usually don't tend to put in components unnecessarily. They are there for a reason. Even more so when located near a CPU. Personally, I wouldn't risk turning it on until it was fixed, but it is your laptop so your decision.

To find the value and type of components you would need to have the schematics.

You would also need to have a boardview file of the motherboard, which shows the component layout of the motherboard and more importantly the component's board designation which is needed to find the component in the schematic to get the information you need.

Once you know the value, search on places such as mouser.com, digikey.com, element14.com etc to find the part

The best that I can find out is that the motherboard is an LCFC NM-D562.

I couldn't find a free download for the boardview, so you will have to purchase it. (This is the cheapest that I could find) You will also need to find the appropriate software to open the boardview file to view it as well

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The board view in the picture is the one for the laptop, I managed to find schematics, but a technician told me Bypass caps won’t be listed in there

15 de out de 2023 por Tushie

@tushie

I won't argue with a tech but you might want to check out the capacitors shown on p.18 (on the left side) as some are hooked up to a "CPU" voltage supply.

Did the tech mention how they knew what the value/type is, of the missing components?

15 de out de 2023 por jayeff

I can’t post images in replies so I can’t ask for confirmation if what I’m seeing is right

15 de out de 2023 por Tushie

@tushie

You can "edit" your question (click on Options > Edit) and post in that or post in a new answer below

15 de out de 2023 por jayeff

Updated / Added a new answer

15 de out de 2023 por Tushie

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bill @ruggb Rep: 4 mil 3 2 · Answer 2 · 2023-10-15T05:48:05-07:00

bill @ruggb

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Postado: 15 de out de 2023

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Many times, the mfg will not place all the components that the PCB provides for. The picture does not appear to have solder on those pads, so I doubt that there was any component there. It is not unsafe to operate without them if they were there. However, the computer might be unstable.

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There was almost surely something there, there probably isn’t any solder because I wiped the area with IPA and some cotton swabs

15 de out de 2023 por Tushie

Wiping with IPA isn't going to remove solder. If the computer runs OK, don't worry about it.

15 de out de 2023 por bill

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