Service manual

Principles of Operation
Vx voltage supply circuit
When the +24 V power supply line reaches 18.6 V (18 V + 0.6 V), transistors Q25
and Q26 go on and Vx (+5 v) is output. If the +24 V power supply line drops
below 18.6 V, Q25 and Q26 go off and the Vx voltage is extinguished.
The Vx voltage prevents abnormal operation when you turn the printer on or off.
When you turn the printer on or off:
l
The Vx voltage circuitry is reset and does not drive the printer until the power
supply stabilizes.
l
Full-ups for the printhead signal lines prevent printhead malfunctions.
l
Pull-ups for the paper feed motor signal lines prevent paper feed motor
malfunctions.
Figure 2-24. Vx Voltage Circuit
2-24
LQ-200/AP3000