You can dismantle the dehumidifying unit and bring it to Tagore Lane (if it's DigiCabi) and let them check. Mine stopped working in the beginning of this year, I think, but the guy said it's not the dehumidifier unit that's spoilt... it's just the power adaptor. And he offered me a new adaptor for $15. Cheap cheap!
Or if you want even cheaper (which is what I did), you can head down to Sim Lim Tower and hunt for an adaptor unit that gives the same current and voltage, and you gotta make sure the plug head is the same too. Abit more work, if u ask me, but I got mine for $8... definitely worth the $7 saved, to me... =)