Hi!
You have two options for this, both options will require small/micro soldering.
You can either replace the USB-Type C port, or the whole main board. The one to choose will primarily depend on which part you are able to source. For this replacement you will need some basic tools and a soldering iron.
You will need to open up the headphones, and you can follow the Marshall Major IV 컨트롤 노브 교체 guide to access the main board, up to step 5 (then the guide continues for something else).
After that you will need to remove the main board from the ear cup, remove the three screws and the ribbon cable. I do not know how the USB-C port is secured to the chassis, so you will have to figure that out. Now, take lots of pictures, especially of all the cables! You should be able to carefully lift up the main board without desoldering the cables and thereby be able to see both sides of the main board. However, you may have additional things secured to the backside of the main board, so be careful!
Now comes the hard part, finding replacement parts. As said before, you will either replace the USB-C port, or the whole main board, depending on what you can find.
For USB-Type C port:
- Now that you have access to both sides of the mother board, you can look at how the USB-C (also called USB-Type C) port is soldered to the main board. You can search online for Marshal USB-C replacement and similar to see if you can find purpose made replacement for your headphones. Or, search for general USB-C SMD (surface mounted device) components. Most resellers will publish specification sheets alongside the components by which you can check if you can find any USB-C port with the same dimensions as the ones in you headphones. Continue with any search terms that comes to mind, and you should hopefully be able to find resellers that are appropriate to your location.
For Main board:
- Search online with all the search terms that comes to mind, such as Marshall Major IV main board part. Look at all the different markings on the board and search for any that seems like a PCB ID, and check both sides of the board. E.g. whatever the stickers says, the "H020_MB_...." could also be something, e.t.c. Use varied search terms and try a few different search engines.
Next step after you've gotten the replacement component will be to desolder things. I quick tip is to use solder flux for desoldering and re-soldering! This will make the process much easier and will increase your success by a lot!
- For replacing the USB-C port, you will need to desolder the port, and the solder the new port in place. To access the both sides of the board well enough to solder the USB-C port, you may need to desolder all the other cables on the main board (once again, take lots of pictures and make sure you can tell the cables apart!).
- For replacing the main board, desolder every cable from the main board (with lots of before pictures). Put in the replacement main board, and solder everything in place.
Take you time and you will be able to succeed, and please return and tell us how this went!
Good luck,
Cheers
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