Perhaps you could help a fellow technician out , So the school I work for has about 4 faulty HP 22 All-in-one computers.
Whenever power is plugged in and machine is turned on I get four beeps and it does not even show POST screen.
I have looked up the fault code of 4 beeps which points to thermal problems however I have taken this computer completely apart , cleaned all components and fans furthermore went to the trouble of replacing the thermal compound yet I still get 4 beep codes with a red light.
Thank you for posting on HP Support Forums. It is a great place to find the help you need, from other users, HP experts, and other support personnel. I see from the post that your computer is not booting into the windows anymore,
First off, Hats off to you for a job well done as you have tried the basic troubleshooting steps and checked settings on the unit, before posting the query in the HP forums. It is amazing to see how technically competent you are. It is always a privilege to work with tech-savvy customers like you.
As I understand you have already tried cleaning the components as well as replacing the thermal compound. I would suggest this could be a hardware failure. Before you could contact our HP Phone support for available service options. I would suggest you try these steps here:
Step 1: Performing a power reset if your computer does not start
If your computer does not start, first reset all power to the device. Hopefully, the problem is temporary and can be fixed by performing the following steps:
Disconnect all peripheral devices such as printers, USB storage devices, and media cards.
Disconnect the power cord from the computer.
Press and hold the power button for at least 15 seconds until the power LED on the power supply is off.
Reconnect the power cord, and press the Power button.
If you have followed the steps suggested and still having the issue, I would suggest you contact our HP phone support for available service options. If your product is out of warranty, please choose paid options to get the tech support number.
Please use the following link to create yourself a case number, then call and it may help speed up the call process: