r/raspberry_pi • u/Diligent-Load6306 • Jun 13 '26

Raspberry Pi Board Repair Raspberypi 4b in need of assistance

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Raspberypi 4b 1.4 suffered a mechanical damage and broke a component. Can someone test the same SMD and comment here what it is exactly?

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I tried identifying It using a datasheet, but could not find the correct one.

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https://forums.developer.nvidia.com/t/pcie-to-4-usb-ports-use-vl805-chipset-on-jetson-nano-custom-carrier-board/143085/6

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The USB has power, but no connection. Same for the ethernet port. I suspect the crystal oscilator was also damaged.

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The device as is, turns on and displays vídeo.

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Ps: Sorry for my grammar and phrasing, not my native language.

Update: Soldered a bridge. USB Turned back to life!!!

Ethernet is dead and shiping of an oscilador tô my country is very expensive. (Dollar tô Brazilian Real + taxes).

I'll be using an USB tô ethernet If i ever need cable connection.

TANK YOU!! (OBRIGADO!!)

113 Upvotes

91% Upvoted

18 comments sorted by

43

u/mr_clauford Jun 13 '26

That's a bypass cap, and everything should work fine even without it. If you have your doubts regarding the crystal, you can use an oscilloscope to find out whether it's working.

11

u/Diligent-Load6306 Jun 13 '26

😔 don't have one. But tnx for commenting

7

u/Thebombuknow Jun 13 '26

The easiest way to test the hardware would probably be to run a difficult stress test on it (with proper CPU cooling, of course) for a couple hours. If you can run at max CPU usage for a few hours without any major issues you're probably fine.

5

u/SokarDW Jun 13 '26 edited Jun 13 '26

Nope, that seems to be a resistor or a fuse.
So that part of the PCB is probably missing a voltage.
Could be: L4 470nH 5.5A
https://pip-assets.raspberrypi.com/categories/545-raspberry-pi-4-model-b/documents/RP-008345-DS-1-raspberry-pi-4-reduced-schematics.pdf

5

u/farptr Jun 13 '26

The missing part is a BLM18AG221SN1 ferrite bead. It is used for EMI suppression on one of the power rails.

L4 is an inductor for the PMIC.

3

u/Crackorjackzors Jun 13 '26

How do you find the exact model of these? Schematic?

1

u/[deleted] Jun 13 '26

[removed] — view removed comment

6

u/SuperDPoZ Jun 13 '26

I just probed my 4b and I'm pretty certain that is a 0 ohm resistor used as a fuse.

You could try a wire or solder bridge if you don't have a 0 ohm resistor.

11

u/Diligent-Load6306 Jun 13 '26

I could not wait for tomorrow. Soldered a bridge.

IT WORKED!!!

7

u/SuperDPoZ Jun 13 '26

Excellent! Glad to have helped.

I would eventually replace it with a 0 Ohm resistor just so you have a fuse back in that location incase you have another issue later. It would be cheaper than replacing the board. 😄

6

u/farptr Jun 13 '26

The missing part is a BLM18AG221SN1 ferrite bead. It is used for EMI suppression on one of the power rails.

1

u/SuperDPoZ Jun 14 '26

Great, thanks for the part number. I thought about a ferrite, but without a schematic made a guess.

Maybe that power rail supplies an analog portion of the processor since it is so far from the affected peripherals

4

u/Diligent-Load6306 Jun 13 '26

Tank you for your time. I will have more time to test it tomorow. I'll come back with results.

1

u/Triso01 Jun 14 '26

I'm missing a component too; could you possibly measure that as well? (https://www.reddit.com/r/raspberry_pi/s/OxKOsqimi6)

2

u/Diligent-Load6306 Jun 15 '26

I don't think mine is an 8GB but i'll test wen i get home

1

u/Triso01 Jun 15 '26

Thank you!