Atari 400 Field Service Manual

400 GREY BAR
TROUBLESHOOTING
(cont)
Verify
that
each of the
foUowing levels
and/or
signal wave
foras
exist before
proceeding
to
the
next step.
Use SALT
II. COLOR
BARS,
locked
into
the continuous
mode.
Is there
3.S8MHz
oeciUation
at
R158
on 'Motherboard.
Refer
Figure
iiamia
NO
Swap-out
XlOl.
Q103
and
QI04
YES
Is there
input
signal
to base
of
Q107 Refer Figure
NO
Trace
circuit back
to
previous
step
YES
Is
there
output
signal from
coilectot
on
QIO? Refer
Figure
NO
Trace circuit
back to
previous
step
YES
Is there
signal
at
J107, Pin
1 Refer
Figure
NO
Trace
circuit back to
previous
step
YES
Go
to
next page
ATARI
Home
Computer
5-16

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)