Originally Posted by
dljorg
Had this problem and thought I should share the solution in my case. Machine is a C6500.
In the end C-C101 is really a 5 volt short problem that causes the power supplies not to start. The pictures above of the rear of the carriage unit are one place the short can occur (and those wires will get loose there if you look at them crooked) but of course any pinched wire will do the same. Good diagnostic for the carriage is to start the machine with the carriage pulled out. If there is a short in there the machine should start normally (if the boards aren't already fried) as the short is disconnected.
In my case the probem was a blown index sensor in the yellow write unit laser!
Customer reported the machine was running normally but just shut down with the C101 code and that was the end. By checking the indicator LED's on the Printer Control board and Image Processor board with a working unit we could see that 5 volts was missing. Got confused because we replaced just the printer control which promptly blew out again without any visible positive result. Next time by we did the Printer control and the Image Processor board at the same time with known good parts taken from another machine. Machine lit up but promptly gave C-4714 for the yellow write unit index sensor. Shut the thing off fast (which saved the printer board but not the IP) and based on some experience with shorts and lasers from way back at the start of C6500's, replaced all four write units, another printer board and another IP board.
Replacing all the lasers may seem like overkill but the last time I experienced a laser short chain of events it turned out that a single shorted laser had ruined all four lasers and the printer control board, VERY expensive fix. Multiple lasers here was a response to that bad day.
Also replaced the wire bundle running from the lasers to the Image Processing board as it appeared physically chewed up (but a lot of them do).
Observations:
Soldered on fuses are an expensive service result for a cheap engineering solution
Wish I knew more about the indicator LED's on the Printer and Image board (admit I have not yet checked on this forum for that info)
Best diagnostic move for this problem in this case was replacing Printer and Image board at the same time with known good parts (only power up after both boards are installed). Doing it one at a time just blew up the new board with no indication that anything changed.
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