My Heng Long Tiger smoke unit worked for 2 hours and died, the displacement pump is on and can hear the noise from it. After the search on the forum and before order the replacement, I found the smoke unit for the SS tanks usually the first part to be broken and people have different reasons for the failure. I suspect it would be a design flaw, and if so, get a replacement will finally has the same result, run 2 hours and die again. Therefore, I decided to tear down the smoke unit and find out what is going on.
My smoke unit is made of clear plastic and can be see-through, I used a regulated DC power supply to juice the unit at 7.0V, (in case as others suggested the unit need a fresh charged battery, otherwise not powerful enough to heat the smoke out, but I figured the power source is not the origin of the problem) motor pump runs but still no smoke in the chamber then I used a model knife to cut open the smoke chamber (about 23mm cube), and there is a cotton pellet with aerosol at the bottom of the chamber (also contradict to some suggested, the cotton pellet is not the source of the problem since this pellet is right at the bottom of the chamber, and far away from the pumped air inlet and smoke outlet, this cotton pellet will not block or clog the smoke), a thick wick that is twisted with the heating element, the element is then soldered to a little circuit board and wired out to the power source. After careful examination, I found the heating element came off from the solder joint on the board, then I untwisted the wick and separated the heating element from it, since wire of the element was come off and only half of the length of the element can be reused (it has only 5 ohms in resistance, so the stock would be 10 ohms I guess), resoldered it and connected to the power supply, the bare element started to heat up the little aerosol residue on it and for 2 mins without burn out the element (so burn out of the element due to aerosol dry out for short time should not exist). Then I found a cotton wick only 1/3 of diameter of the stock one, put 2 drops of aerosol, put back everything and seal the chamber up, power up with the stock battery about 2/3 charged, WOW , a lot of the smoke was generated and came out from exhaust (see the YouTube video).
Since the heating element only half length so it generates more heat than the stock and gives out more smoke, therefore, a repair now become a mod.
The conclusion is the stock smoke unit is only good for like model train, but not for HL tanks. The reason is the wick is too thick and when put too much aerosol in it, it will soak up and gain a very â€śheavyâ€ť weight, (actually the even excess aerosol will go down to the cotton pellet at the bottom of the chamber as a reservoir and will not hurt the unit) however, HL tanks usually run at rough surface, doing super spins and recoil, this kind of shock, vibration and force give a great stress on the tightly twisted and soldered heating element and finally broke up and cut off from the soldered joint or the wire itself by the weight of the stock wick (the heating element works like seat belt and the wick likes an over weighted adult). Finally, the suggestion not to put too much aerosol into the stock smoke unit is right in order to prevent this happen, and if you have a broken smoke unit, you may try to do this repair by replacing with a smaller wick and resoldered the element and enjoy the mod.