Editing Atari 400 Capacitor Replacement Guide (section)

== Voltage & Ripple Check ==

After recapping and reassembly, verify the power rails at the mainboard edge connector or test points:

{| class="wikitable styled-table" style="width:70%; text-align:center;"
|+'''Atari 400 Power Rails (No Cartridge, BASIC READY)'''
! Test Point !! Expected Voltage !! Max Ripple (p-p)
|-
| +5 V (logic) || 4.90 – 5.10 V || < 50 mV
|-
| +12 V (video/audio) || 11.5 – 12.5 V || < 100 mV
|}

* Use an oscilloscope (20 MHz bandwidth) to check ripple if available.
* Excessive ripple or unstable voltages may indicate a faulty power supply or incorrect capacitor installation.