Refill instructions for Brother LC-121 with syringe

The inner ink tank of the Brother LC-121 is protected by a two-piece outer housing. To refill with ink, it is necessary to remove the outer case of the Brother LC-121.
On the back of the Brother LC-121 cartridge there are two holes per part of the outer case. The retaining lugs of the inner ink tank snap into these holes.

The front housing cap above the ink outlet and air inlet can be removed by carefully pressing in the retaining noses with a small screwdriver and pushing them to the right in accordance with the first two images. The cap can then be easily removed from the ink reservoir.

At rear half of housing, holding noses are a little bit more difficult to reach. Please be particularly careful here. Push the noses inwards and push the inner tank to the left according to the first two pictures.
Finally, the inner tank can easily be pulled out of the rear part of the housing.

Several places on the outer frame of the ink chamber are suitable for attaching the filling opening.
In Variant 1, drill a hole in the top left corner of the front of the ink tank next to the air inlet opening. As you can see in the lower left picture.
For Variant 2, drill the filling opening into the top of the tank frame on the side facing away from the air inlet. The middle, lower picture shows the position.
For your better orientation we have removed the side foils of the ink tank - this step is not necessary for filling.
The lower picture on the right shows you a closing option for variant 1 (the right stopper in the picture) as well as for variant 2 (the stopper on the upper side in the picture).

For variant 1 it is sufficient to remove the housing cap via ink outlet and air inlet. Place the filling opening in the upper left corner next to the air inlet opening. Use this hole to fill in the amount of ink required for the cartridge type. Close the filling hole with a suitable stopper or use hot melt adhesive.
Push the front cap of the housing back onto the ink tank until the retaining lugs snap into the openings provided. The stopper is pressed firmly against the frame of the tank and securely closes the filling opening.

For variant 2, please remove both the front cap and the rear part of the outer housing.
Fill the ink chamber with the appropriate amount for the cartridge type. Be careful not to damage the side foils of the tank when filling with syringe and cannula. Close the filling opening with a suitable stopper or use hot glue. Replace the rear part of the housing on the inner tank and press it firmly until the retaining lugs snap into place.
There is enough space for a flat sealing plug. The stopper is pressed firmly against the sloping part of the housing and securely closes the filling opening. Finally, push on the front cap until it also snaps into place.