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I broke what looks to be either a diode, capacitor or resistor on the board of my pi 4B they are related to the hdmi output i guess and I want to try and replace the surface mounted component(all four highlited components are broken). I know the chances are pretty slim, but I cannot try without knowing what I need to get.

these are the components i broke :

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  • all four of them Dec 27, 2022 at 19:09
  • this is the picture of a healthy board i have Dec 27, 2022 at 19:14
  • in the broken one they're all ripped off Dec 27, 2022 at 19:15
  • check the schematic diagram and the mechanical drawings to determine which components are those
    – jsotola
    Dec 27, 2022 at 19:36
  • (1) You don't need to use SMDs. You can just use through hole replacements; (2) Ref: raspberrypi.stackexchange.com/questions/104596/…. Good luck.
    – tlfong01
    Dec 28, 2022 at 3:29

2 Answers 2

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Welcome! Start with the understanding that without experience it will probably never work again. Purchase some resistors, they are less then $2.00 per thousand 0805. Get a value and size you will use. While you are waiting for them to come in and the other needed parts, also get some flux and SMD soldering paste. You will need a hot air gun for SMD rework, SS tweezers, cotton sticks and isopropyl alcohol, I use 91%. I have a soft brush and normally rinse my boards with very hot water add some liquid soap and scrub, rinse and air dry, they come out nice and clean. If that does not work you probably used rosin core and the alcohol will work for that. Now get some junk/scrap boards with SMD parts on them. In your free time watch several videos on SMD repair etc so you are familiar with it. You may even find another tool or so you may want. Now remove and replace parts on the practice boards, when you are comfortable take your time and go after the real thing. Good luck and let us know how you make out.

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Yes you face some problems as there's probably less point in trying to replace those chips if you don't know what values the missing ones were (unless you have the ones that got knocked off in a bag somewhere?) Apart from the black chip resistor the rest are chip capacitors however that doesn't really help you much without their values. If you were able to obtain another pi board of the same spec and revision to get the missing values your course of action and tools required would be as follows. Tools: fine tipped (preferably temperature controlled) soldering iron. Fine gauge flux cored solder wire. (Depending on the age of your assembly I suspect the solder will be No-clean but no reason technically why you can't use tin/lead rosin cored solder wire for a repair to a lead-free assembly.) If you are going to use lead-free make sure the iron you buy is capable of reaching the higher temperature of lead-free solder and that you use the correct flux. If you use rosin flux you may want to buy a flux cleaner aerosol and stiff bristled pencil brush but not essential, and a decent pair of stainless steel tweezers. (Worth spending £20 plus for one pair tweezers. Cheap is crap is worthless) No reason at all why you can't hand solder chip components using flux cored solder wire, but unless you have a calibrated temp controlled iron it is preferable to avoid direct contact between chips (capacitors in particular) and the soldering iron tip, so tin the pads lightly before placing the chip. Melt a bit more solder onto the outer end of first pad then use tweezers to offer the chip such that the chip termination is up against or directly sitting on the bump of solder. Hold the chip there, making sure the other end remains flat on the other pad, then place the iron tip onto the solder bump away from the chip. Meaning keep a gap between iron tip and chip. As you melt the solder watch for the solder to fuse between solder on pad and tinned chip termination. Now touch the iron tip onto the outer end of the other pad and melt solder wire onto the pad and it will flow toward the still to be soldered chip termination, ensuring no direct contact between chip and iron. Ok this all sounds difficult but it isn't really and after a couple of tries with surplus chips you'll be fine. (I've done loads over many years it's no big thing, you don't have to go down the more expensive solder paste and reflow route for repairs / rework and you can still maintain IPC soldering standards.) If you can get a duplicate pi you can read the resistor value with your eyes but you need to de-solder each cap, measure it with a multimeter and re-solder.

I should add that the smaller the chips the smaller the PCB pads for those chips, which means the net adhesion between the pad (and chips soldered onto them) and the PCB laminate is not strong. So when your chips were knocked off were the pads pulled off too? Have good look as a couple of those chips look like 0603 so very vulnerable to pad delamination.

Good luck

Nick

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  • Please structure your answer into chapters, as it is now its just a BIG text blob.
    – MatsK
    Dec 30, 2022 at 15:20

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