Fuser Control - Epson EPL-5500 Service Manual

Operating Principles

2.1.2.3 Fuser Control

The heater lamp, powered by AC voltage, heats the fuser. When the power supply board receives
a FUSER signal from the main board (C169 MAIN-B), the power supply board (PWB-E) supplies
the AC voltage to the heater lamp. This AC voltage is cut by an interlock switch when the case is
open.
Thermistor TH1 detects the surface temperature of the upper fusing roller and inputs that analog
voltage to the 77-pin chip, IC201. Based on this temperature data, the heater lamp on/off signal (the
FUSER signal) is output from the 54-pin chip, IC201, causing heater lamp H1 to turn on or off to
control the fusing temperature. When the heater lamp is not turned off even if the thermistor detects
a high temperature malfunction (which occurs if the surface temperature of the upper fusing roller
exceeds 200º C), the signal from the 75-pin chip, IC201, changes from H to L to turn off the heater
lamp forcibly.
C169 MAIN-B
IC201
77
54
L
IC202B
75 5
6
H
The following figure shows the fuser temperature control procedure.
Temperature
(Degrees C)
Figure 2-15. Temperature for Fuser Control Procedure
1. Warm up: After printer initialization, printer warm up starts, and the heater lamp turns on until
the upper fusing roller's temperature reaches approximately 172º C.
2. Standby: In standby mode, the upper fusing roller's temperature is controlled to maintain 156º C.
When this condition continues for 3 minutes, the printer goes into standby mode at low
temperature.
3. Print cycle: When the printer receives the printing command from the controller, the upper
fusing roller is controlled to maintain 172º C.
4. Standby at low temperature: The upper fusing roller is controlled to maintain 112º C.
2-10
5 VDC
IC202A
H
2
3
4
1
3
L
H
H
4
L
Figure 2-14. Fuser Control Circuit
172
156
112
Powe r On
Warm up Standby
EPL-5500 Service Manual
Analog Voltage Detected by the
Thermistor (TH1)
CN202
1
2
CN207
1
1
PWB-E
5 5
CN1E
Heater Lamp
ON/OFF Signal
L H1:ON
H H1:OFF
When a print is made immediately after warm up
Time
Standby with Low
Temperature
TH1
Thermistor
Heater Lamp
CN3E
1
H1
2
3
TF1
Thermal Fuse
Rev. B