DNA 75 - HCIGAR VT75 nano/Resistance problem

[Loxias]

Hi all!

I've got a HCIGAR VT75 nano almost two months ago.
I use two RDTAs, AVOCADO 22 and Fodi F2 and vape on TC using SS316L of 0.32mm (28AWG) making single resistance between 1 and 1,3 Ohm. Watt 11 to 13. Temp 200 C (392 F).
Few days now, I face the below problem.

The resistance made on a 3mm axon with 10 coils (spirals) and it should be 1,17 ohm according to Steam Engine. My DNA reads it at 1,21 ohm. It's OK. If we take in account the mod/atomizer internal resistance, it's OK.
After a short time of vaping, DNA reads it at 1,18 and after a while at 1,12 ohm, then at 1.0 ohms and then malfunction is starting. The temperature indication is going mad showing a series of craze indications, i.e. OFF, 33554, OFF, 84, 125 (these are temp), OFF, 33554, 80, 121, OFF, 33554 and so on, until Temp protection is taking over, even if i set it on 290 C. Vaping is impossible.
I suppose this is a kind of short-circuit but I cannot guess more. Especially the 33554 indication is a mystery for me. Please note that it happens to both AVOCADO and FODI atomizers!

Putting both atomizers on a Joyetec vtc mini, everything is OK.
The readings are correct and the vaping is normal.

May I have your help/suggestion please?

Thank you!

[Daddi89]

Got this kind of problem in the past few days while using a kf5 clone, sorted them by just unscrewing, cleaning and screw back again the top part of the hybrid 510.

[yoseff]

That VT75 nano has also that screw in the bottom? (Think they call it cathode or some thing like that)

I remember VT75 had some weird problems with that

Also what is the value you have in "Mod Resistance"? (escribe)

I would clean everything very well, and would use a "shortcircuiter" tool in order to get the right mod resistance.

You can look around in forum in how to get something like that, or you can DIY. Did mine with a plume veil base and a brass screw to have that good short circuit and discover each device's resistance.

Hope you find solution for that

[gidzol]

I had the same problem.

I took the VT75 Nano apart and found that the grounding screw felt out (see picture). I screwed it back and since it is working fine.

          

[Francisco Garcia]

Good morning, I got a lostvape DNA75. I only use steel resistors (316L of 24 or 28).
Sometimes it does temperature control, or not. Sometimes you are doing CT, and change tank and stop doing it and it only works in WW.

Anyone know if it's normal if it's broken?

Thank you

[steamer861]

So just encountered the very same issue, I tried a chip swap, cleaning all my ground points in side the mod, all with no results.
I then tried unscrewing the top cap of the 510, cleaned the threads real good & replaced it nice & tight, voila it works fine again

[Wayneo]

Francisco Garcia said:

... Sometimes you are doing CT, and change tank and stop doing it and it only works in WW.

The majority of these problems are boiled down to a connection issue. Either faulty or loose wiring, a dirty connection, or a loose connection within the build itself. 

[Daddi89]

So, last week im back having issues with the ohms reading, decided to take it apart and found that one of the mounting screws was broken, the top left one, replaced it with a new m 1.4 x 5mm and tightened the other two, cleaned again the top 510 negative cap and is back working flawlessly.
Must to admit now, this mod has a very great look, but the engineering is crap.

[orome]

Not sure if this is a good topic to post my question but here goes nothing. I owned Joyetech VTwo 75W mini and an eLeaf PICO 75W TC. Now I own two Hcigar VT75 nano with na evolve DN75 chip.

 I was used to making SS316L ga28, 2.5mm, coils in the range 0.7-1.5 ohms and using them in TC. The resistance did not jump while vaping. With Hcigar I uploaded the SS316L profile from steamengine and in this instance used Kayfun v5 atomizer. The resistance of the atty is about 0,77 ohms in the morning when I wake up. The mod is set to SS315L material, 14W, 250C. I take a vape and the resistance jumps to 0,93 ohms after a second or two. If I leave the mod alone and let it cool down the resistance eventually gets back to around 0,77 ohms, and when I take another vape the same thing happens. Is that normal behavior for a DNA mod in TC mode or am I missing something?

[VapingBad]

No, I would check your connections and that the outer of the 510 is clean and tight, also I would use a coil under 0.5 ohm on the 75 or you may hit the voltage limit and not get full power.

[Loxias]

I found out that I've got the same mechanical issues which faced by gidzol and daddi89.
The VT75 nano started to behave like a mad. I took it apart and voila!
An internal screw was completely unscrewed and two others were loose.

In conclusion: That said by daddi89: "this mod has a very great look, but the engineering is crap"

[FairCold]

Any one got any idea how to permanently fix this. From my experience, all this problem is due to non-solder connection. This non-solder connection will formed oxidised layer over the time and cause unstable resistance. Hope someone creative can come up with good idea. Or may be a new C frame that is pre-installed with 510 plate.

[dl12345]

To add another report about this issue, I had the same problem with my VT75 nano. I disassembled it and all of the screws mounting the board were loose - both ground screw and mount screws. Additionally, the 510 plate and the battery plate threads were still very dirty with machining residue. I cleaned both the plates and receptacle threads with isopropyl alcohol.

I'm tempted to wire the ground directly to the 510 base plate to avoid this nasty non-solder connection that FairCold rightly criticized, although that's going to require a little surgery.

On a side note, the 510 connector is a poor quality part - the 510 positive is a simple metal plate on a spring (and it's not copper either) housed inside a plastic holder. Unfortunately, the profile of the plastic housing is quite thin and the battery positive is directly underneath the 510 positive, separated by a plastic insulator. As a result, it doesn't support replacing the 510 with a better quality part such as a FDV v4 as the 510 positive wire comes out at right angles to the positive plate and there's no clearance.

A possible solution would be to machine a 22mm threaded cylindrical housing on a lathe (with a lip on the top end to bolt on the 510) that will raise the connector and allow clearance, but I don't have access to a lathe. 

[FairCold]

I have managed to solve unstable resistance value on my vt75 nano without soldering. What i did was remove the pointy tip on top of positive 510 connector using a file. This can be done by disassemble the 510 connector. Once pointy tip was removed, i tighten the 510 plate(negative terminal) to C frame. Tested with escribe device monitor, the graph is even smooth compared to before the changes. So far the resistance value is stable.

[dl12345]

FairCold said:

I have managed to solve unstable resistance value on my vt75 nano without soldering. What i did was remove the pointy tip on top of positive 510 connector using a file. This can be done by disassemble the 510 connector. Once pointy tip was removed, i tighten the 510 plate(negative terminal) to C frame. Tested with escribe device monitor, the graph is even smooth compared to before the changes. So far the resistance value is stable.

This fix also stabilised my resistance readings. It's almost like the 510 positive has been extruded and leaves behind a little raised part when the extrusion process is complete. I used 600 grit paper, although it's a very soft alloy, so you can use finer paper. Smoothing it and flattening it makes a superior contact surface.

[dl12345]

As a followup to the last post, I find I still need to remove the 510 plate regularly and clean the threads on the plate as well as the threads on the case. It appears that (possibly) oxidation builds up in the threads over time and messes with resistance. If it's not oxidation I'm not quite sure what it is (it's not liquid I don't think because my attys don't leak). Cleaning it with a cotton bud and isopropyl alcohol works

[Daddi89]

I was just going to ask if you find any improvement overtime...

We should try with some noalox and see if it will keep up longer.

[Kostant]

Look at this link

http://www.esigarettaportal.it/forum/156-battery-box/61324-ufficiale-hcigar-vt75-nano-dna75/page53

post 525 and 526

This may be a definitive solution

I made the fix and it works

Bye

[Daddi89]

grazie compare, dopo vedo di farlo pure io appena torno a casa a Londra, non entravo piu su esigarettaportal da anni...

Ops, sorry guys...

[Kostant]

@Daddy89 Ciao paesano

[FairCold]

Kostant said:

Look at this link

http://www.esigarettaportal.it/forum/156-battery-box/61324-ufficiale-hcigar-vt75-nano-dna75/page53

post 525 and 526

This may be a definitive solution

I made the fix and it works

Bye

can some explain it in english, i can't understand from google translate. how is the washer is connected to the 510 plate? soldered or just a touch connection?

[Kostant]

@FairCold

The washer is connected to the 510 plate by the compressed mechanics connection that is created when you screw the 510 plate to the box case .

 

[Daddi89]

So ATM there are two possible way to fix this damn mod, the issue is caused by the not so proper connection between the atty gnd and the board ground (caused by a silly engineering by hcigar) overtime the 510 plate will oxidise and fucks up the gnd connection (crated by the 510 top plate, the black plate just down this one and mostly the entire body)

First way to fix her (and easiest to do) is by remove a thin layer of the 510 black plate (just under the removable 510 hybrid plate) with some sand paper (i used 180) then wrap with an aluminium foil the outer part of the battery box (not the board part) till the inside, including the 510 (so in this way youre going to create a new conductive layer between the two parts of the body and between the two 510 plates) and then remove the excess over the positive 510 pin (just the center ofc) and battery.

Second way (not so difficult but not so dumbproof like the first one) is to solder an electrical wire to the other ground connection on the board itself, peel the cable and leave it between the two 510 plates. plus if you want, add another one at the bottom of the board and leave it between the battery cap and the battery itself. (following this procedure you will have 4 wires in total soldered to the board instead of the original 2)

For now i did the aluminium foil trick, will update in the next days/hours and see if there are still any resistance fluctuation overtime.

[FairCold]

Daddi89 said:

So ATM there are two possible way to fix this damn mod, the issue is caused by the not so proper connection between the atty gnd and the board ground (caused by a silly engineering by hcigar) overtime the 510 plate will oxidise and fucks up the gnd connection (crated by the 510 top plate, the black plate just down this one and mostly the entire body)

First way to fix her (and easiest to do) is by remove a thin layer of the 510 black plate (just under the removable 510 hybrid plate) with some sand paper (i used 180) then wrap with an aluminium foil the outer part of the battery box (not the board part) till the inside, including the 510 (so in this way youre going to create a new conductive layer between the two parts of the body and between the two 510 plates) and then remove the excess over the positive 510 pin (just the center ofc) and battery.

Second way (not so difficult but not so dumbproof like the first one) is to solder an electrical wire to the other ground connection on the board itself, peel the cable and leave it between the two 510 plates. plus if you want, add another one at the bottom of the board and leave it between the battery cap and the battery itself. (following this procedure you will have 4 wires in total soldered to the board instead of the original 2)

For now i did the aluminium foil trick, will update in the next days/hours and see if there are still any resistance fluctuation overtime.

Can u share picture of the modification that u have done. I didn't really get the idea of it. I meant for the first method Thanks..

[Daddi89]

FairCold said:

Can u share picture of the modification that u have done. I didn't really get the idea of it. I meant for the first method Thanks..

http://www.esigarettaportal.it/forum/156-battery-box/61324-ufficiale-hcigar-vt75-nano-dna75?p=936693&ampviewfull=1#post936693

my phones battery died and i couldnt take any, i just did like him edit: after 3 hours of standby ohms cold ohms are rock solid (usually i was having a 0.01 ohm increase every hour of standby)