turntable problem--???????need help

I am running a SOTA Saphire/MC Gold/PT-6 arm. Whenever I turn turntable off using the on/off switch I get static through the speakers- I have replaced the switch, no differnce-I have used 2 different pre-amps--no change--I have turned off the amp and hooked up headphones to the preamp--no change--still get static when I shut machine off. I have the turntable groung wire connected to the ground in the wall and the PT-6 arm ground connected to the ground terminal on the EAR Phono pre-amp.
I have sent the unit to SOTA--they have "extensively tested" the motor/assembly/power supply and can't duplicate the problem.
If they can't duplicate it, they can't fix it.
Any ideas as to what could be wrong?

That's the only problem w/system, everything else works fine-no hum, no static when turned on or any other knobs/dials activated.

I'm wondering if the problem is on my end and not the turntable.
Have you tried to put all the grounds in one place? 'Star' grounding is often the answer to such gremlins. Give all grounds only one potential path ... perhaps the static is not the table, but your preamp's phono section losing it's link to the ground THROUGH the turntable. Try it. Let me know if I'm right or not.
Try installing a .01uF 200V cap across the AC switch contacts, to snub those nasty counter emf switching transients.
the advise from Bob Bundus worked. I soldered a .01uF, non-polarized capacitor in series witha 1 ohm 1/4 watt resistor. I hooked this across the 2 contacts on my on/off switch and the problem was solved. the resistor is required to counter any efects that the cap might induce,ie, too much discharge of energy.