I bought ultrafire WF-139 from buyincoins for under 8 dollars. Worked fine for about 15 minutes and then - bang/pop and all the charging lights were off. After receiving 5 dollar coupon from BIC, I opened the charger up and saw a smoke sign on inner case and a exploded resistor. I would happily replace it, but due the explosion it's hard to see the resistor code. Picture (large)
Should I attempt to repair it or just throw it away?
Someone who has that charger could tell you the number of that burned resistor. Try to change it.
AVIOD Buyincrap at all cost! They are notoriously known for counterfeit products, especially the WF-139. I bought one myself, which worked for a few days and broke, it overcharged every cell i put in it before it stopped working.
TOSS IT! unless you have home insurance. ;)
I have tried to search internal pictures of wf-139 but haven't find the same design as mine (internal design seems to vary a lot, at least 3 different designs). Maybe some BLF user has the same charger with same design and can help me 
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WF-139 chargers are great , However buy from a reputable company..(Manafont, DX..)
I have a not working Ultrafire charger (get it, do never work) and the resitor do not exist on my charger - maybe this is the reason, why it don't work. It would be nice, if someone who has a working one could open it and inform us about the resitor typ.
I've tried opening mine, but the bottom part of the back plate won't budge.
I saw photo's somewhere of it pulled apart. Sounds like a fake.
This is one of the worst soldering quality I have ever seen...
Try to use with a 12V power adapter.
dont know if this helps
It is possible that other component were damaged so, unless you can have any component free and you have some time to lose, i'll throw it away.
There is a screw under the sticker. This must be removed to open it.
Long time no update. The 12V socket does not work either. So complete junk.
Will be replaced by Xtar WP2 II (ordered) or sysmax i4 (received but not tested yet)
I purchased a Ultra Fire Wf 139 & 4*18650,the problem is the charger cuts at 3.84v, in each cells,green led status for more than +5hrs or so but still the voltage is 3.84.Can any one tell if the charger is bad or all the cells.
In the meantime I contacted Dx & they are ready for giving replacement or store credit,but I somehow feel what if the new batch of Wf-139 chargers are all undercharging or perhaps the 4*Tf Flames what I got are all defective ones,any one reads this post plz reply and give opinion whatever in ur opinion.
My WD-139 charger from BIC came with a faulty bay that did not charge, opened it up to find some components had been burnt up. Replaced the charger with the same one from DD, still works today. Though I have ordered the solarforce charger that looks similair exept it can charge 16340 cells too because the WF-139 is 0.5mm short of taking my protected 18650 batteries.
Thankx Pacbough for the reply,
2 more thing I noticed.:-
1>When there is no cell in the charger & the green leds are on,the voltage displays in the DMM is 4.96v
2>I opened the charger & can see there are several dry solder cuz the surface is pale,so can it be a reason of undercharging.
Does undercharging damages or lower the power of Lion cells ?
I thought they were a highly reputable company selling original products only.
I didn't now it had a 12v socket
Hi, everybody!
I have an Ultrafire Charger WF-139 from 5 years. I’m charging an old 18650 type batteries from laptops. The cells are unprotected. I haven’t any problems. Charger works well. 
You’d save lots of time with a better charger.
HKJ’s test concludes:
The charger does not follow the recommended charge procedure for LiIon batteries, but it does charge to 4.2 volt and then turns off. It takes a long time to charge 18650 batteries, but 16340 and 14500 are charged fast.
I believe that it is a useable charger.
Full test here: Review of Charger UltraFire WF-139