Hey bud, congrats on making the switch to vaping and welcome to the underground! I am sorry that you're having problems with your tank. If you bought it from a store and it's defective parts like it sounds like and they guy won't take it back then I would definitely take your business elsewhere...and if you bought it off another vapor...again I would take your business elsewhere. I can give you a list of recommended places to shop if you'd like as well as several other members of the forum.
Now, as to your problem....I don't know if you're getting metal pieces coming off the copper plate...but maybe you're getting intermintent "soft" shorts coming off your coil from the copper plate you're using to make the connection causing your resistance to jump around making your coil misfire and that can be dangerous and as a result...as your resistance drops you're getting a quick spike in wattage as your mod is trying to compensate for the changes in resistance. I am not sure if this is the problem but I know when I accidently push the button and turn my wattage up way higher than my coil can handle it can have a metallic taste as well as a dry hit taste. I've done it with both my Kayfuns and my stock OCC coils. are you using the the prewound one's that come with the tank or are you using your own homemade coils?
Do you have an ohms meter you can screw your base into? If you do...then screw your base in with your copper plate modification you've done and poke around the rda deck with at toothpick as well as wiggle it with your fingers...if the coil is properly secured in the base and you wiggle the rda deck screwed against your copper plate you put in it to make it work and the resistance starts jumping around than stop using it that way. it's not making a good connection and is more than likely the cause of your problems.
Once again I am sorry you got a bad RDA deck...my friend had problems with the RDA deck that came with his Subtank mini...it had the wrong size screws in it and one of the screws to trap the leads...the hole for it was threaded out of the box and wouldn't trap the wire properly and was useless. I gave him mine since I just rebuild the OCC heads but if you're deck is bad I strongly suggest not using it and just getting an ohm's meter and some 26 gauge Kanthal and learning to rebuild the Stock OCC heads...I am not sure if Kanger just sells the RDA deck but I am sure you can google it or someone else will come along and know where to find it if they do...you can always buy another tank from a reputable store like 101vapes and have a backup and use the RDA deck off of that and if you have problems then you can switch them out and return it then till you get it right.
It always sucks and is a horrible and dissapointing feeling when vape gear doesn't work right out of the box and you have my sympathy. Maybe you could post more pictures of your fix as well like the copper piece inside the base without the RDA deck screwed in or pictures of the bottom of your RDA deck and we can see if we can come up with a better fix in the meantime. Best of luck to you and here's to hoping we get you better vaping. Oh, I would just order a 5 pack of stock OCC heads as well...it doesn't hurt to have one or two around if your RDA head wick burns out or something while you're out and about and can't rebuild and need a coil on the quickness...its always good to have a spare around
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