IH power supply failure

I was having lunch at the office when a call came in for a Bizhub 552 that had stopped working and was displaying an error code. The customer was good enough to read us the code which was C-3B07. I knew from memory that codes starting with 3B are problems with the inductive heating system in the fuser. These codes have stuck in my memory as I have had a couple of difficult jobs that started with these codes.

We had a look at the service manual and confirmed that C-3B07 is the IH power supply reading a low input voltage. While the service manual tells us to check the supply voltage, fuser and heating coils first we know from experience to skip all these and go straight for the IH power supply board itself. 

Do we have the part? A look in the parts manual for the part number and then a check of the inventory shows us that we don't. What we do have is a couple of C552 colour copiers that I can pull parts off. While the 552 is the same as a C552 except for the lack of colour imaging units I wanted to check that the power supply was the same but my boss said not to worry about it. "Of course it will be the same". So I grabbed the board and headed out.

First I reset the error and then restarted the machine and as soon as it tried to print the error came up again. That's good because I hate intermittent faults.

It only took me 15 minutes to change the power supply and start the machine up again but then another error comes up! C-3B02 this time. A look in the manual says that this error occurs if an incorrect IH power supply board has been installed in the machine or by a general CPU error.

The first thing that comes to mind is that I have the wrong board. I am thinking that no, a C552 IH power supply does not fit a 552. I am about to call my boss and let him know that he has stuffed up but decide to compare the part manuals for the two machines first. Interestingly my boss was right and the board is the same  for both machines.

 So why the error? I know the IH power supply worked in the C552 at the office so why won't it work now? It is the right part for this machine so the first part of the error description in the service manual is wrong. That leaves the general IH power supply CPU error. The printer control board in the back of the machine cannot talk to the control chip on the IH power supply board. 

Since I know the board worked before I touched it then my next thought is that I caused this fault. How? The obvious answer is that I forgot to plug a connector in.

I pull the covers off and have a look. The connector for the wiring that runs from the printer control board to the IH power supply looks good as do the coil terminals. But the input power connector? I forgot that completely. My only excuse is that it is at the bottom of the board while all the others are close to the top. However the connector I missed is three times the size of the others and has some heavy gauge wire so it is normally hard to miss. 

Once that is fixed I check the other connectors again, put the covers on and power up the machine. It works great.