Don't bother... Weller stuff is junk... that's why you're trying to
repair the the one you have... lol
Do yourself a favor and try one of these...
http://www.hexaconelectric.com/thermo.html
They ain't cheap... but man do they last.

Weller makes junk better than your junk by maybe 40-50 dB.
Thanks for your unsolicited opinion.
W4ZCB