MPM UP2000 Lamps won't turn off completely-Help

Hi, I need help with our MPM UP2000, the stencil and the lamp boards won't turn off completely, they are both on at the same time. Turning it on would only make it brighter, turning it off will just lose the brightness but the lamps are still on. I have checked I/O3 and the SSR's are all OK. I have checked the U3 board where the lamps is connected and it is OK as well. I need to know where the control of the U3 board is coming from, I have a feeling this is where my problem is. Any advise on what could the problem be would be greatly appreciated. Has anyone had this similar problem? Thank you.

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