TM
11-6625-3041-30/TO
33A1-8-908-12
1-27. MULTI VDC (A1) DC SUPPLIES
General
There are five DC Supplies. The four main ones (+12, +5, -5.
and -12V) supply power primarily for use by external-circuitry.
One (+12V Run Ref) supplies power to the start circuitry on the
Multi VDC card (refer to para 1-24, Start Supply). All operate
in the same manner.
Energy at 20 kHz is supplied by the Switcher to the primary of
Operation
flyback transformer T1. This energy is transformed to the
proper voltage level at the secondary, rectified by a diode,
and filtered by one or more capacitors.
Internal
Each supply incorporates an internal load to protect the supply
Loads
against possible damage by overvoltages in the absence of an
external load. The +12V and -12V supplies use a 511-ohm resis-
tor at the output. The +5V supply uses a 56 ohm resistor at
the output. The -5V supply uses a 20.5-kilohm resistor located
in the fault sensing reference circuit. The +12V Run Ref uses
two 511-ohm resistors located in the Ref Sel circuit.
Dual
The secondary windings for the +12V and -12V DC Supplies include
Voltages
a tap so that these supplies can be used to supply either 12 or
10V.