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31 December 1992
10.3 FUSING TEMPERATURE CONTROL
Overheat Protection
+5
+24
1K
IC107
6
_
1.3K
5
+
C
P
U
10.3.1 Fusing Circuit Operation
The fusing lamp is powered by AC controller 1 and controlled by the main
board.
AC controller 1 receives direct wall voltage ac power (not stepped down) at
T304 and T306. It also receives +24 volts at CN301-5. The ac power is
applied to the drive circuit, the fusing lamp (L3), and the triac (TR). The dc
power drives PC301 and RA301.
To turn on the fusing lamp, the main board drops CN107-A15 to LOW. This
activates the photocoupler (PC301) which in turn energizes the drive circuit.
The drive circuit turns on the triac to complete the lamp circuit, thus turning
on the lamp.
RA301 guards against a failure of the +24 volt power supply. When +24 volts
is applied at CN301-5, RA301 is energized and its ac contacts stay open. If
the +24 volts power stops, the ac contacts of RA301 close, stopping the drive
circuit and turning off the fusing lamp (U.S.A. version only).
+24
7
Q101
CN107-A25
24
CN107-A15
A.GND
CN107-B25
CN110-12
+5
CN110-11
CN110-9
CN110-10
AC Controller 1
CN301
-5
PC301
-6
RA
301
-3
T309
RA301: U.S.A. version only
2-43
FUSING AND PAPER EXIT
AC115,220,240
T304 T306
Drive Circuit
RA301
T310
T308
T307 T305
G
TR
L3
TH1
TH2
TF1
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