Project information

Title : Repairing a HP AIO with no power

Date : 01/04/2026

Description : Repairing a HP AIO desktop by diagnosing a faulty capacitor and then replacing it

Problem : The HP AIO was not showing any signs of power and would not turn on.

Overview

- System had no power at all (no LEDs, no response)
- Tested power adapter → confirmed working
- Measured voltage on motherboard → little to no voltage present
- Initially unsure if probing correct points
- Noticed slight heating near IC by power input → suspected possible short
- Reconnected power → spark/pop occurred
- Found damaged SMD capacitor in parallel capacitor bank near input rail
- Used bench power supply (19.5V, current limited)
- Voltage initially wouldn’t rise properly → indicated load/short behaviour
- Increased current limit gradually
- Board began responding:
Power LED came on
Power button LED active
- Beep codes present (adapter-related)
- Switched to original adapter after confirming stable behaviour on bench supply
- System booted successfully
- Removed damaged capacitor
- Measured out of circuit → low resistance (shorted)
- Re-tested board:
Normal voltage present
System powers and boots correctly

Verdict:
Fault caused by shorted input decoupling capacitor
Removing faulty capacitor restored normal operation