Konica Minolta 7075/FORCE 75, Service Manual

Page: 151 / 844

2 - O - 5
FIXING UNIT
PRCB
DCPS2
DCPS1
ACDB
L4 TS2
TH1
TH2
TH3
TH4
RL1
CBR2
(7075 only)
TRC1
TRC2
TS1
L2
L3
TH1 ANG 1
TH1 ANG 2
TH2 ANG 1
TH2 ANG 2
TH3 ANG 1
TH3 ANG 2
TH4 ANG 1
TH4 ANG 2
L2 CONT
L3 CONT
L2&L3 CONT
L4 CONT
5VDC
SGND
24VDC
PGND
24VDC
RL1 CONT
AC(H)
AC(C)
L4 DRIVE
L2 DRIVE
T3 DRVG
L2 TRIG
L3 DRIVE
L3 TRIG
[4] Fixing Temperature Control
METHOD
REPLACEMENT
MODEL
7075/7085
MANUAL
SERVICE HANDBOOK
REVISED EDITION
3
DATE
Jan. 2002
PAGE
2-O-5
3
The fixing upper roller is heated by L2 (fixing upper
roller heater lamp 1) and L3 (fixing upper roller heater
lamp 2) and the fixing lower roller is heated by L4 (fixing
heat roller heater lamp 3) via the fixing heat roller. The
PRCB (printer control board) detects the temperature
of the fixing rollers using TH1 (fixing unit temperature
sensor 1) and controls L2, L3, L4 via the ACDB (AC
drive board).
1. Operation
a. Temperature control
The PRCB turns ON the fixing heater lamp circuit
in ACDB as soon as the main switch is turned
ON, causing L2, L3, and L4 to go ON until the
fixing upper roller reaches the specified
temperature. Series/parallel switching control is
performed over L2 and L3 to prevent flicker
(fluorescent lamp etc.). Immediately after L2 and
L3 are turned ON, they are connected in series
to suppress rush current. Then they are
connected in parallel. TRC1 (triac 1), TRC2 (triac
2) and TRC3 (triac 3) are used for this series/
parallel switching control. The series/parallel
switching circuit is provided with CBR2 (circuit
breaker 2) to prevent short current from flowing
when a operation error or fault occurs.
Set temperature: 200°C
Warm-up time: 6 minutes or less (at room tem-
perature 20°C)
3