MK114 Problems with LOW VOLTAGE LIGHT ORGAN

After I connected LOW VOLTAGE LIGHT ORGAN to supply (12Vdc) and speaker input, the light (12V, 5W) is constantly on (even if potentiometer is in low position). Now I am trying to figure out what is wrong. It would be very helpful, if I had schematics. Is it possible to get it?

Thanks and best regards,

Diagram has been mailed to you address.
Keep us informed.