By "wobbly" I mean I can grab the wheel head on either side & move it up & down (like a tetter-totter but not that drastic) with the rest of the wheel not moving. The wheel head is level it's just seems loose. I've been using the wheel for about 4 years & it hasn't given me any trouble, nor has it had anything fall on it or heavy dropped on it. This might just be a slow wear that has only become noticeable recently.
Mark - Where have you found replacement parts for model-a? Looking at the Amaco/Brent site I couldn't find any information about model a's but they do have two wheel head options.