Atari 400 Service Manual

2. Refer to Figure 5-3, for correct screen display.
• Check the V’s in the upper right of the screen to be sure they are
not inverted.
• Observe if any of the vertical bars are missing or appear in a
different sequence than Figure 5-3
Figure 5-3. Any Video Test Screen Display
G = GRAYBAR TEST
1. Enter Command Letter 'G', carriage return (or spacebar).
1. Refer to Figure 5-4 for screen display appropriate to this test.
• Screen is divided into eight equal horizontal bars.
• The shading begins with the horizontal bar at the top of the screen
being black and increments gradually to the bottom horizontal bar
being white. The top four horizontal bars can be noticeably
different in color shade than the bottom four horizontal bars.
5-10 System Service Manual

Atari 400 Specifications

General

Manufacturer	Atari
Model	400
Type	Home Computer
Release Year	1979
CPU	MOS Technology 6502
CPU Speed	1.79 MHz
ROM	10 KB
Operating System	Atari OS
Keyboard	Membrane keyboard
RAM	8 KB (expandable to 48 KB)
Graphics	ANTIC and GTIA chips
Sound	4 channels
Display	RF output for connection to TV
Storage	Optional cassette tape drive or floppy disk drive
Ports	Cartridge
Display Resolution	320x192 (16 colors)