Loss of power in an HP M4555 MFP


A few days ago I was called out to work on a HP M4555 MFP machine that didn’t have any power—no lights on the control panel or formatter board, no fans, no anything. The call was through a National Service Provider (NSP) so a customer service technician had diagnosed the machine over the phone and a low voltage power supply (LVPS) was sent to the customer’s office to be replaced.

When I arrived onsite I tried a few quick troubleshooting steps and decided to go ahead and take a look at the LVPS and noticed that one of the two fuses on it had blown. Since the NSP had sent out a replacement power supply, and I already had this one out, I decided to install the new LVPS.

Typically, when you have a blown fuse, simply replacing the fuse or the board fixes the problem. Unfortunately, once I replaced the LVPS, put the machine back together, and turned it on I heard a loud popping noise and the nice smell of electrical components burning.   Continue reading