Epson FX-870 Service Manual page 135

The +5 VDC voltage-overload protection circuit cuts the +5 VDC line output ifthe voltage exceeds
The +35 VDC line has a voltage-overload protection circuit and a voltage drop protection circuit.
The +35 VDC voltage-overload protection circuit cuts the +35 VDC line output if the voltage exceeds
The voltage drop protection circuit protects the printer against a sudden voltage drop that may be
caused by a short circuit in the secondary circuitry of the +35 VDC line. Ifa voltage drop is detected,
it stops the operation of the switching circuit and then the output of the +35 VDC voltage.
An external switch is used to turn printer power on or off. When the power switch is turned off,
the switching circuit is de-energized and the output of the +35 VDC voltage is stopped. However,
since the switch is in the secondary circuitry, current continues to flow in the primary circuitry as
long as the printer remains plugged into an external AC power source. For this reason, you must
disconnect the printer fi-om the external AC power source. Unplug the power cable from the AC
power outlet before you perform any maintenance work.
6-20 Epson FX-870/1170