Ricoh Aficio SP 420dn shows SC545 error code after

sc545 means fusing section over heat. try 7-807 to reset

As NALDZ said, sometimes when the power drops out the thermistor will play up a little. Sometimes this can be caused by toner being caked up on the thermistor. But in most cases it can be reset easy enough.

if you walk up to the machine in COPY mode.
simply press.

(yellow clear), 1 , 0 , 7 (hold red stop button)
The screen will change, if you hold '#' on the keypad and press 'copy sp' on the touch screen you will be into ricoh service modes.

All you will have to do now to reset your error is simply switch the machine off at the main red switch below the plastic flap toward the bottom of the machine.

problem solved =]

ta!
Willi
Service Engineer