T12 iron head does not absorb tin, generally there are two reasons:
A. The head of solder tip is severe oxidation can not absorb tin.
B. Temperature can not rise up then can not tin.
C. The head is oxidized and can not the tin, you can use the soldering iron to clean the ball gently, then use the wet sponge rub and then heat the tin.
D. serious oxidation of tin, you can use more than 900 mesh sandpaper gently rub, with a small wooden board,
in the board to dig a small hole, put the rosin and tin in the hole, put the head of solder tip insert the hole, while heating and putting the tin,If you can prepare a tin stove, use scaling powder into tin stove put the tin to repair!
E. If T12 temperature can not rise up, the multimeter transferred to 20Ω stalls, test T12 solder tip positive and negative ring resistance. 8-10Ω belongs to the normal range, the factory standard is 8.4Ω, after using the resistance will be slightly changed!