CYRUS AV5 TECHNICAL DESCRIPTION
July 2000
5
Microprocessor
The microprocessor forms the interface between the user controls to the various circuit blocks. At power up
and power down the processor is reset by IC1105. The amount of output lines is boosted by IC’s
IC1205/6 adding an extra 16 control lines.
Power Supply
The power supply is linear and regulates to:
+5V for miscellaneous digital circuits
+5V for the CODEC
+3.3V for the DSP
+/-12V for the analogue circuits
+/-6V for the volume controls circuits.
All regulators are 78XX series except for the 3.3V design which uses an LM317 adjustable regulator. The
transformer includes a re-settable thermal fuse which will trip under short circuit conditions. A separate
supply C113 has been included for the muting circuit to prevent power off thumps.
Display
Display contrast is set by R1313/1314. The back light is turned on/off by T1301/2/3.