Download the manual and verify proper assembly. Correct any issues like an improperly wrapped Balun or the air variable capacitors being out of sync with the knobs. Make sure all mounting screws especially the Allen set screws are tight. Copy the tuning guide from the manual for quick refrence. Always tune up on low power and progressively increase TX power while tweaking the tuning. Properly and precisely tuning will never result in arcing even above 2500 watts.