Editing Atari 400 Troubleshooting Guide (section)

== Audio & I/O Failures ==

=== Audio Issues ===
* No sound in games or Memo Pad:  
** Suspect '''POKEY''' chip (C012294); swap with known-good if socketed.
** Check speaker wiring and TV volume.
** Inspect for cold solder joints at the modulator and audio output.
=== Keyboard & Joystick Problems ===
* No key response:  
** Reseat keyboard ribbon; clean contacts.
** Test with another keyboard if available.
** Inspect for broken traces on the keyboard PCB.

* Joystick not detected:  
** Clean joystick port; check for broken solder joints.
** Faulty POKEY or 4050 buffer IC may cause input failures.