Irruptive Current Control Circuit - Toshiba MR-3011 Service Manual

10.2 Irruptive Current Control Circuit

CN8.1
RADF open/close switch
CN8.2
OPNSW
CN8.3
CN8.4
Jam access cover switch
CN8.5
JAMSW
CN8.6
CN1.1
CN1.2
+24V Power sourse
CN1.3
CN1.4
This circuit controls the irruptive current flowing into the current regeneration condensers (C40 and C112)
mounted on the drive circuits for the read motor and reverse motor to a certain value. The circuit consists of a
posister (PTH1) which controls the current and FET (Q14) which supplies the current in normal conditions.
Base current is not supplied to Q8 and it becomes OFF after the RADF open/close switch and jam access cover
switch are turned OFF till the cathode voltage of ZD5 reaches the zener voltage. At this time, both voltages are
set by R111 and C53. Q14 is turned OFF correspondingly to supply the current to PTH1.
When the cathode voltage of ZD5 exceeds the zener voltage after the time allowance given by R111 and C53, a
base current is supplied to Q8 to turn it ON and Q14 comes ON correspondingly. The current limitation is
canceled and the current flowing in the PTH1 starts to be supplied to Q14.
R74, R112, R127 and R128 are discharge resistors to capture charge stored in consisting C40 and C112 right
after either of the RADF open/close switch or jam access cover switch is opened. The circuit consisted of R87,
R114 and Q8 captures the charge stored in C53 right after either the RADF open/close switch or the jam access
cover switch is opened, and also controls irruptive current for instantaneous opening/closing of the cover.
October 2000 © TOSHIBA TEC
TP30
1 1
*DFOPN
2
DFOPN
3
+24V
4
DF+24V
5
CVROPN
+24V
6
*DFOPN
+24V TP26
FUSE1
1 1 2 1
+24V
2
+24V
C22
3
PGND
1
4
PGND
PGND TP25
TP41
C_OPN
R73 ZD4
1 2 2 1
DF+24V
1
R134
2
PGND
1
R87
2
R71
1
1
1
R111
2
2
1
PGND
C53
2
PGND
10-2 MR-3011/3012 DESCRIPTION OF CIRCUITS
+5V
1
R110
2
1
C 2
1
Q7
B
E 3
SGND
PTH1
2 1 TP39
3 2
1
Q14
C52
R128
1
2
R74
R72
2 1 2
C1 4
ZD5
1 3
2
B
1
B2
C2 5
R114
1 2
PM+24V
1
1 1
R112
2 2
1 1
R127
2 2
PGND
Q8
2
E
PGND