Power Supply - Radio Shack TRS-80 Service Manual

2.8.2
-12VDC
REGULATOR
(Figure 2-8)
The
voltage
generated by the
35VAC
center-tapped secondary winding
of
the transformer
is
used as
input
to
the -1
2VDC
regulator. This input
is
rectified, filtered,
and then regulated
to
maintain
a constant
-12VDC
output.
17 5
J002
P002
T
'
13
VAC
35
VAC
F
ov
15 17.5
VAC
ELECTRONICS
BOARD
HALF
WAVE
DIODE
RECTIFIER
FUSE
12V
REGULATOR
-12VDC
TO
CIRCUITS
±OV
Figure 2-8.
-12
VDC POWER
SUPPLY
2.8.3
+35VDC
POWER
SUPPLY
(Figure 2-9)
The 27.5VAC
output
from
the transformer
is
rectified
by
a
full-wave diode bridge and
filtered
by
C1
to
generate the
+35VDC
unregulated
voltage applied
through fuse
5ASB
to
the
driver circuits
and paper motion
solenoid.
J002ITJ
+
C1
*
—
\/W—
*•
I
R1
I
CAVIT Y
-±OV
T
,
27.5
J002 P002
16
VAC
27.5
VAC
17
RET.
10
10
-P002-
4
FULL
WAVE
DIODE
BRIDGE
RECTIFIER
TO
CIRCUITS
+35
VDC
1
FUSE
5ASB
•
+
OV
ELECTRONICS BOARD
•1005
T
„
0TO
PAPER
MOTION
SOLENOID
Figure 2-9.
+35
VDC POWER
SUPPLY
2-8