Not a konica Minolta tech. this machine came to my territory, user said it was working fine until he replaced CMY image units. Machine fires up fine, starts initializing and then control panel goes black like it has a short. Have checked all on/off and interlock switches OK. I have reinstalled old image units back with same result. Can some one give an idea? Thank you very much. ML.

It is never a good idea to have users installing the Imaging Units. I use to work on the C-350s & C-351s when I worked for a KonicaMinolta company and never encountered this when replacing the IUs. Had to make sure that the IU is properly shaken to loosen up the preloaded toner/developer mix. If this doesn't happen the copier will usually code out with some type of developer motor lock code, it maybe that if they didn't shake up the IUs well enough that the motors could have drawn enough of a load to burn out some component on one of the boards. Good luck with it.

Do you get the hour glass on the screen or anything at all or does it stay black the whole time?? I have never seen changing the IU's cause something like this you can also take the panel off it's very easy and there is only one ribbon connector to the panel in the past I have had to take panel apart to clean(works sometimes) I have replaced the panel and if you follow the ribbon cable it connects to a PWB under the glass behind the CCD assy .. sometimes this can be caused by a bad NVRAM or firmware ..

thank you for your support, there's a bulletin to correct this problem, image processor board needs to be replaced. thanks everybody ML.

Well as the bulletin said replacing the image processor board would fix it, but it didn't. Now what any suggestions please reply. Thanks. ML

Do you get anything on the display? Hourglass, logo? Any lights? Give us more details on what does happen.

If you haven't make sure to give it a good 5 minutes to do something after you power on both switches.

Try turning it on with the sub switch on first then hold down the Utility/Counter button while turning on the main switch. Hold the Utility/Counter until you get a small circle off to the side of the display or until the "Trouble reset" option comes on (assuming the display will come on with this method).

Have you tried reloading firmware?

After both switches are on, hourglass appears on screen for 1 minute then screen goes black. Will reload firmware and try msp board and see what happens. thanks.