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Maintenance
DC POWER SIJPPLY
Refer to drawing 824-
109632 in section "
Drawings
. The power supply contains
a switching
power supply generating the following DC voltages: +5V
20V
and the high voltage (HV) for the
transmitter (48V).
The supply can operate from an input
voltage between 10V and 40V. The
switching frequency can be between 80 and 250 kHz and may be adjusted
within this range by potmeter R1. This makes it
possible to reduce noise
problems for the receivers by tuning the switching frequency away from the
frequency of the receiver. All of the outputs can be short-circuited or left open
without damaging the
power supply, although input fuse
Fl
may blow.
Connections
Plug PI is
connected to the backplane.
Plug P2 is connected to the DC power source.
Plug P3 is connected to the high
voltage.
LED
LED indicator: +5V
OK.
Test points
POWER SUPPLY
+5V
20V
+20V
a. a. a. a. a.
Bypass control signal
Ground
Shutdown of reg.
(active low)
co
I'-- co
1.0 ~
('I) C\/ ~
a. a. a. a. a. a. a.
I- I- I- I- I- I- I-
in (10- 40)
Sw. Freq. (80-
250 kHz)
A V dd
(typical 12V)
High voltage negative
High voltage positive
Ext. power shutdown input
(CD486)
Figure
11
Test points on the DC power supply.
P3405E/B
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