I have to agree with your father that it possibly is the power supply unit (PSU).
Here is the Maintenance and Service Guide for the computer. It will give you all of the information that you need to do anything that you need to do on it. Also, here is the Troubleshoot a problem section for the computer. At the bottom of the section is the Power section. It will help you troubleshoot the PSU. You can use the Troubleshooting section to review all of the other components.
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