Problem with a K4003

I have soldered a K4003 kit and it does’nt work. There is a mistake between page 6 and page 10 of the notice. In page 10 a strap is made for the mute system and not in page 6. I have put this strap and the amplifier does’nt work. With a 50 VA transformer the power supply is +18,5 V and -18,5 V. If I cut the strap, with a little input voltage I can see a sine wave at the output, but with a higher voltage I get a square wave. The diagram in page 11 is not correct and does’nt match with the block diagram of the manufacturer.
Have you a solution for this problem?
Thank you for your answer

If you mount the strap, the amp will be muted, so it is normal that it does not work. It is normal that the amp produces square waves if the input is overdriven. Input sensitivity is 300mV for max. output.
Remove strap and test with music signal.