Atari 800XL Technical Service Data

PRELIMINARY SERVICE CHECKS (Continued)
SERVICE CHECKS
SEE INTERCONNECTING DIAGRAM AND PHOTOS TO MATCH THE NUMBER IN THE
CIRCLES WITH THOSE IN THE FOLLOWING DATA FOR SERVICE CHECKS TO BE PER¬
FORMED.
(?) KEYBOARD
(A) No clicking sound when a key is pressed. Check
GTIA 1C (U17).
<B) Keyboard is dead. Check the 1C U17 and POKEY
1C (U22).
(C) One key is erratic. Clean the key.
(D) One group of keys does not work. Check 1C U22.
(E) START, SELECT or OPTION Function keys or
SHIFT, CONTROL and BREAK keys do not work.
Check 1C U17.
(F) Wrong characters appear on the Monitor Screen
when the key is pressed. Check the ANTIC 1C (U7),
and IC’s U17 and U22.
(7) SOUND
(A) No sound. Check the adjustment of the Sound Ad¬
just Coil (L202). See "Miscellaneous Ad¬
justments" and check 1C U22.
(?) CASSETTE
(A) Cassette motor will not start. Check PIA 1C (U23).
(B) Cassette save or load does not work Check
POKEY 1C (U22).
(?) JOYSTICKS
COMPUTER DEAD
(A) Unplug the Power Pack and check for 5.0V from
pin 3 to pin 1 of Plug P7. If 5.0V is missing, check
Plug P7 and the cable for possible open circuits.
If the Power Pack is bad, check for a possible
short from pin 3 to pin 1 of Jack J7 with the Power
Switch (SI) in the On position. If a short exists Do
Not plug in a new power pack until the short is
repaired.
(B) If the Power Pack is good, turn the Computer
On and check for 5.0V on the positive end of Elec¬
trolytic C2. If 5.0V is missing, check the Power
Switch (SI).
COMPUTER DOES NOT COME UP PROPERLY
(A) Check the CPU 1C (U8), GTIA 1C (U17), POKEY 1C
(U22), ANTIC 1C (U7) and RAM IC’s U9 thru U16.
VIDEO
(A) No video. If RF Modulator output is being used
check theChannel Switch (S2) for correct channel
and check the Channel Adjust Coil (L201). See
"Miscellaneous Adjustments". Also check the
ANTIC 1C (U7) and GTIA 1C (U17).
COLOR
(A) Color not correct or no color. Check the adjust¬
ment of the Color Control (R38) and the Channel
Adjust Coil (L201). See "Miscellaneous Ad¬
justments" and check the ANTIC 1C (U7) and GTIA
1C (U17).
SYNC
(A) No vertical or horizontal sync. Check GTIA 1C
<Ui7).
(A) Joystick button does not work. Check GTIA 1C
(U17).
(B) Joystick position functions do not work. Check
PIA 1C (U23).
@ PADDLES
(A) Paddle button does not work. Check PIA 1C (U23).
(B) Paddle control does not work. Check POKEY 1C
(U22).

Atari 800XL Specifications

General

Manufacturer	Atari
Type	Home computer
Release year	1983
CPU	MOS Technology 6502C
RAM	64 KB
ROM	24 KB
Operating System	Atari OS
CPU Speed	1.79 MHz (NTSC) / 1.77 MHz (PAL)
Graphics	ANTIC and GTIA chips
Display resolution	160×192 to 320×192 pixels
Sound	POKEY chip
Storage	Cassette tape, floppy disk
Ports	Serial, parallel, monitor, joystick ports