Hello guys,
Few months ago, i bought a VOX AD100VT and I bought some cheap footswitch(Soundking) for that.

And here comes the problem.

With higher output from guitar, gain or master volume if the FS is connected, amp just starts switching channels like crazy, sometimes its like 5 times per second.
Our second guitarist has same amp and FS, but his amp is ok. I tried my FS on his amp, everything was ok too. His footswitch on my amp and it did the same switching as with mine.

I sent my amp back to guitarshop for repair, and got it back last week. They said everything is ok. Brought it home, put the FS in, and it does the same thing.

So, I'm asking, does anyone know where is the problem? Could it be the ****ty Footswitch just damaging my amp and my friends one not? Or they just fixed it badly in guitarshop? I was thinking about getting a original VFS2, but it's quite expensive for me right now.

Please, give me some advice.
Thank you, and sorry for my english, I'm not a native speaker.
If it works fine with his and not yours then no its not the footswitch. Its gonna be something internal doing it. As its pretty much a SS amp diagnosis can be a serious and expensive problem. If the footswitch isnt connected does it do it. You said in your post you sent it to get fixed but the way you said it you didnt send the foot switch to. If its the switching part of the amp you may just have to do without a footswitch.
Hey, the Valvetronix are notorious for electronic problems. I have now had two different Valvetronix series amps. They both are the older series before they switched the color scheme. The first one I had was the AD120VT 2X12 combo amp and the electronics were so quarky but I love the sounds I could get out of it, so later I found the ADH120 which is the head only, and a matching cab and that thing hasn't had any problems. I have read everywhere about electronic problems with these. If you can get passed the weird nitches I swear by em. I also looked into sending my AD120VT in to get fixed but for what I payed for it, it wasn't worth. I'd also say try a different cable from your footswitch to your amp. I heard if those things get at all messed up they mess with the channels really bad. Is the connection on those newer Valvetronix series from the footswitch to the amp an ethernet/cat5 cable? Just wondering.
It sounds like it's just the footswitch.