Yogiboy appropriately mentioned tonearm / cartridge mismatch as the most likely culprit. I agree. Your response assumes the vendor would not sell you a mismatched combination, but that may not be true.
Look up the effective mass of your tonearm as well as the rated compliance of your cartridge. Go to vinylengine.com, open a free account, and surf to their cartridge resonance evaluator. This will calculate your resonant frequency. The higher the compliance, the lower the resonant frequency on any given tonearm.
As an owner of a Technics TT with an aluminum arm, the arm mass can be pretty high. I had the same problem running a Shure V15-III. The problem resolved when I installed an Ortofon Concord, which has a lower compliance AND lowered the effective tonearm mass (no headshell or fastener mass).

