Did you get a manual with the unit? Is it set up correctly?
When you initiate a start do you hear the motor startturning (somewhere underneath the platter)? It would be real quiet and vibration-free or it would not be very good for use on a turntable. Is the drive belt attached? See the picture in the link.
What do you mean by the STOP mechanism? What do you mean by ON position?
How many pops? How long?
Manual Motor STOP occurs when the tonearm is swung to the right onto its rest.
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As with any turntable the following advice for this one will apply:
The tonearm setup is critical for proper tracking. Do it again with extreme care if mistracking is your problem.
I found one model online and a review with some sample of music. Quite interesting...
http://www.everythingusb.com/ion_ttusb10_usb_turntable_13231.html
The author complained about some things that clearly mark him as a stranger to finer turntables. Complaining about having to assemble and position the 'rubber band', aka the drivebelt, and the tonearm counterweight shows that he underestimates the precision required for a mechanism to rotate at a constant precise speed while properly tracking the microscopic undulations of the groove without skipping into the air or gouging it to death.
Some basics when recording from a turntable...
1) Place the turntable as far from speakers as possible on a solid surface that you will not touch during the recording
2) Keep the volume low enough that airborne sounds don't cause mistracking of the stylus *
3) Avoid anything that will cause vibration or movement of the turntable. (Tip toe)
* If you have a subwoofer, turn it off.
Some advice after reading the article: don't try to save recording time by playing the discs at 45rpm. The best tracking of the disc and recording of the minute details in the grooves will be at the nativespeed of the recording. Digital manipulation later only gloms up the accuracy you probably want.
In general, the fewer the conversions steps in the analog domain, the better; and the fewer the bit rate conversions in the digital domain, the better.