Epson LQ-2550 Technical Manual page 90

Vx
2.3.1.1 (Drive System Pull-up) Voltage Supply Circuit
Figure 2-37 shows the Vx voltage supply circuit.
The Vx voltage is used to pull up the bus for the control signals transmitted to the power on reset on
reset circuit, and drive circuits. It is also used to pull up the output of the buzzer drive IC (66).
"R21
After the printer power is turned on, the + 5V line reaches about 4.7V, and a potential of about 0.6V
When the + 5V line drops to about 4.7V or less, Q2 and Q 1 turn off so that the Vx line drops to OV.
Therefore, each IC is reset, and the control circuits stop operating.
R2
ZD
4 . I v
R20
R21
Figure 2-37. Vx Voltage Supply Circuit
PT SOLENOID DRIVE CIRCUIT
RESET of E05A02LA
OUTPUT
2-43
(2A)
of
IC (6B)