FAURE-HERMAN
COMPONENT MAINTENANCE MANUAL
744-082 / 744-082-3
28-49-91
PAGE 9
MAR 31/07
(b)
+ 13 V control
The filtered 28 V mains voltage is applied to regulator T4 which delivers a 13 V
voltage regulated by a resistance bridge which references this regulator to 1 V. Once
filtered, this 13 V voltage supplies the signal shaping circuits and the display
brightness adjustment circuits.
(c)
5 V voltage
The + 13 V voltage is divided by a resistor network and applied to the input of
amplifier IC1, which delivers a + 5 V output voltage. Once filtered, this voltage
supplies the temperature control circuit.
(d)
D 5 V voltage
The filtered 28 V mains voltage supplies two cascaded transistors T2 and T3
controlled by pulse modulator circuit IC3, which delivers a rectangular signal. The
transistor output voltage is filtered and applied to the modulator circuit for feedback
purposes. The d 5 V voltage supplies the digital function circuits.
(2)
Command and control logic circuit (See sheet 3)
The main component of this logic circuit is microprocessor IC3 which uses a program stored
in EPROM MN203 to command and control the other components via :
-
RAM IC5 for data storage,
-
a data bus,
-
an address bus,
-
a function selector (multiplexer IC1 and NAND gate IC4),
-
various commands (VMA, IRQ, Reset...).
Control signals for the components are generated by the function selector and are used by the
microprocessor to read from or write in the selected circuit. These control signals are
generated according to the following addresses :
-
8000 : Programme run monitoring (IC11),
-
9000 : Temperature control validation (CNV1),
-
A000 : Address decoder (IC10),
The document reference is online, please check the correspondence between the online documentation and the printed version.
