Power Supply (PSU) Checks


An important part of any restoration project is thoroughly checking the power supply unit (PSU) of the equipment you intend to restore. A fault with a PSU could potentially render the whole units electronics dead so its critical that you ensure that the PSU is operating as designed.

Take notes/pictures before removing any cables or dismantling or removing any parts.

I tend to take the same approach with most of the items I acquire and that is:

Visual Inspection

  • Remove all PCB’s from the chassis (Take Anti-Static Precautions) and place in Anti-Static bags.
  • Remove the PSU(s) from the device and any PCB’s that may make up the PSU.
  • Clean the PSU and it’s PCB’s using compressed air.
  • Inspect the PSU components and the PCB’s for any obvious signs of failed components – bulging or vented capacitors, melted components and burnt tracks etc.
  • Inspect PCB’s for cracked connectors and all cabling for damaged wires. 

Pre-Power Up Checks 

  • Check the input resistance to ensure you don’t have a short circuit between Live and Neutral 
  • Check you have a short between Ground and the Chassis (if applicable). 
  • Identify the Gnd for the low voltage side of the PSU and check for shorts between it and all of the low voltages the PSU produces.

Power-Up Checks

  • Rebuild the PSU and return it to its chassis.
  • Reconnect any cabling required for the Input side.
  • Leave the low voltage output side disconnected or the chassis empty of any PC’s
  • Apply Input Voltage and check that you have each voltage that is expected and that they are within tolerance for the device – leave on and recheck in an hour.
  • Once you are happy the PSU is providing the correct voltages and they are stable I check for noise on the DC outputs (using an oscilloscope).

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