Could you tell me how many beeps you are hearing during the power up sequence?
In addition, did something specific happen before this issue first started? Or did it just seem random?
The beeps indicate that your iMac is failing the Power-On Self-Test (POST)
This test checks the Mac’s hardware and RAM (random access memory). It resides in the Mac’s ROM (read-only memory) and runs at startup (though only from a currently shut-down Mac; it won’t run if you simply restart a running Mac). If POST detects a problem, the startup sequence will probably halt almost instantly. In addition, you’ll hear one of the following sounds:
- One beep. Indicates that no RAM is installed or detected.
- Two beeps. Indicates that an incompatible RAM type is installed.
- Three beeps. Indicates that no RAM banks passed memory testing.
- Four beeps. Indicates there’s a bad checksum for the remainder of the Boot ROM. (Checksum refers to a method of determining whether data is corrupt.)
- Five beeps. This means there’s a bad checksum for the ROM boot block.
This information would help further diagnose the issue.