Minolta DEClaser 2200 Service Manual page 39

Safety Circuit
The safety circuit consists of a fixing heater current monitor and a timer
circuit that controls relay RL01. The current transformer monitors the
current drawn by the fixing heater and charges C153. If the fixing current
get too high, C153 turns on Q153, which opens the RL01 contact. The
FSRD
signal also causes C153 to fully charge when a fixing unit error (50
SERVICE) has occurred.
Once RL01 has opened, it is kept open until C153 discharges. C153 stays
fully charged until the ac power is turned off, then C153 slowly discharges.
About 10 minutes are required for the discharge. If you turn the power back
on before C153 discharges, C153 recharges and the 50 SERVICE message
is redisplayed.
SSR Circuit
The SSR switches the fixing heater current on and off to regulate the fixing
unit temperature. The resistance of the thermistor (TH1) varies according
to the heat of the fixing roller. The dc control board measures the resistance
of TH1 and turns SSR on to raise the temperature or off to allow the fixing
unit to cool.
• When the printer is at standby, the fixing temperature is maintained
at 165°C (329°F).
• When the printer starts to print, the fixing temperature is quickly
raised to 180°C (356°F).
The dc control board displays the 50 SERVICE error message if the fixing
unit roller temperature:
• Fails to exceed 30°C (86°F) within 18 seconds after power on
• Fails to exceed 165°C (329°F) within 90 seconds after power on
• Exceeds 230°C (446°F)
• Drops below 140°C (284°F) after the Ready indicator goes on
1–26 DEClaser 2200 Printer Service Guide