Theremax Timbre Trouble?

Hi.
Hope someone can help..
I've got my tmax more or less working. With the Timbre pot turned all the way anticlockwise I get a nice clear sine wave sound.

BUT

As I turn the pot clockwise, instead of the expected square wave sound I just here the sine wave getting quieter as it's gradually replaced with a very faint squelchy distortion sound.

once turned all the way clockwise all I can hear is this quiet garbled sound. (a bit like the sound of an unturned long wave radio).

I've not got a ground plate yet (the thing is still in bits on the bench) which may explain the squiggly sounds but not the lack of a square wave?

Have I got a problem or is the effect just 'very' subtle (the tip about clipping c44 in the faq makes me wonder).

Thanks.

oh it's ok. It was a solder bridge on pin4 of ic1.
It's working fine now.
Ta anyway.