Hi,
Does your x10 probe have a hole in the side with a screw head in it?
Does your scope have a squarewave output teminal?
It is usually a small terminal that you ca clip the probe to, sometimes it has "cal" or a squarewave icon on it, 1Vp-p or 5Vp-p.
If you are experiencing spikes on the squarewave or rounded edges, check the waveform on that terminal, if needed adjust the screw head to compensate for the spikes or rounding.
Tom... 