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SECTION ONE:
INTRODUCTION


1.0   OVERVIEW

The 520STE and 1040STE are designed as integrated units with keyboard, processor, memory, and I/O control in one package. The 520STE has 520 kbytes (524,280 bytes ) of RAM, and the 1040STE has 1040 kbytes (1,048,568 bytes) of RAM. The 1040STE and 520STE both have a built-in 1 megabyte floppy disk drive (unformatted). Both the 520STE and 1040STE come with a modulator for TV output. The 520STE and 1040STE both have the power supply integrated into the case.


1.1   MAIN COMPONENTS

      ∙ 524K RAM (1048K for the 1040STE)
      ∙ Main Board with modulator (except French Peritel)
      ∙ Keyboard Assembly
      ∙ RF Shield (upper and lower) and Power Supply
      ∙ Plastic Case (upper and lower)
      ∙ Mouse
      ∙ Power Supply
      ∙ Disk Drive


1.2   CASE DESIGN

The 520STE and the 1040STE are nearly identical.  The upper case has openings for the keyboard and a lens for both the power indicator LED (front left corner) and the Disk Drive Activity LED (mid right side). (see Fig. 1-1)















Figure 1-1:  520STE Upper Case

















Figure 1-2:  1040STE Upper Case


The left side panels of both machines have slots for the expansion cartridge, two MIDI ports and two game controllers.











Figure 1-3:  STE Left Side Panel


The right side panel has a slot for the floppy disk drive.











Figure 1-4:  STE Right Side Panel


The STE back panel contains (left to right) the modem (RS232) connector, printer connector, hard disk/DMA connector, external floppy disk connector, television output,
monitor connector, power switch, stereo output (right and left), AC power input, and reset button. (see Fig. 1-5)















Figure 1-5:  STE Back Panel


1.3   POWER SUPPLY

The 520STE and 1040STE have an integral switching power supply providing +5V and +12V. There is a 2A fuse. Voltage should be adjusted to 5.1V. The power supply has overcurrent protection; if the fuse is blown, a catastrophic failure is likely, such as shorted primary.


Power Supply Rating

      Current out:            3A at 5V, 0.9A at +12V
      Max. power in:          33.5W


Typical (in system) Demand:

      Typical current:        1.75A at 5V, 86 mA at +12V
      Max. current:           2.2A at +5V, 90 mA at +12 (during disk access)


1.4   NEGATIVE SUPPLIES

The STE motherboard contains two small switching voltage regulators (the TL497 or equivalent) that are used to provide additional voltages.

U204 is used to generate the positive and negative voltages for the RS232C line drivers. These voltages are normally ±12 VDC.

U205 is used to generate a -5 VDC supply for the audio subsection. This output is heavily filtered to reduce the switching noise that might otherwise appear in the audio output.