Do you only have one table? Have you only been troubleshooting through the same channel every time?
- try a different channel on your Vestax
- try a different needle if you have one for your Technics
- try a different phono cable with ground to the same channel
- try a different cable from your Vestax to your soundcard
- try a different mixer (if you have one) or get a phono/line box and go straight from the table to the soundcard
I'm not suggesting that you BUY something new for the above mentioned troubleshooting methods, just if you have another of something, try it to rule that exact thing out. If you go to channel 2 and it's fine, then it's channel 1 on your mixer that's the trouble. But try these methods out as well:
1) Check your needle. Remove the cartridge and lick the 4 points where they screw into the arm, then rub it off on your shirt. Wipe off any dust on your actual needle.
2) Unplug/plug your cables and ground.
3) Unplug/plug your cable to your soundcard.
4) If none of those methods work, check your faders on your Vestax mixer. If you have a removable crossfader, sometimes you need to remove dust from that, or replace it.
Hope this helped.