Measuring Turntable Speed
My prefered method of checking turntable speed is to use a test disc, like this one from Analogue Productions.
You can then either record the signal into a pc, and using the analyise spectrum tool in Audacity plot where signal peaks.
The best tool I have found is PlatterSpeed which works on iphone/ipod/ipad/android. Here is the result from my Diy Turntable.