If you are still having this error (78xx and 79xx) all you have to do is unplug the machine from power and keep it unplug for 2min - while it's unplug take fuser (R8 - behind door A, left side of the machine) out shake and install, plug and power on the machine
Please explain what Repair or Diagnostic is served by shaking the fuser ??
If you have not had any luck you can try a software reset, this can get the machine going temporarily. How to video attatched.
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