[Podmore pottery wheel electrical drawing needed]

'Controller' is perhaps too generous. Check the bridge rectifier and the capacitors. When the smoothing cap across the mains blew in my podmore the wheel didn't even turn. Replacement from Farnell cost a few quid including postage.

Question is really what's pulling the 6 amps?

Hope this helps. 

Podmore Pottery Wheel circuit diagram.pdf

[Podmore pottery wheel electrical drawing needed]

There is nothing too elaborate in the electrics, just have to be very careful as it is mains AC and high voltage DC. Also it is worth mentioning that it is a variac (variable AC transformer) that drives the DC motor through an AC to DC bridge rectifier, not a rheostat as some people seem to think. I have a circuit diagram for reference for my own wheel only, others may be different. In the P67.06 I have there are no resistors, just three smoothing capacitors, one on the AC in and one on each of the Field and ARM feeds for the motor.  The Normand DC shunt motor is rated 0-200VDC and 1.9A max. There is a mechanical limiter on the foot pedal which limits the output from the variac, probably by design, a wheel that is too fast is no use for throwing and also bad for safety.

From what you say it sounds like you have power but just not for "large" loads. I don't know what specified Kg load limit is for this wheel but this wheel is only rated 0.33HP. My wheel happily handles 6Kg. Haven't had a reason to do anything larger.

You might need a wheel with a bit more HP.