Late 2013 27" iMac Not Turning on ~ Just one single beep every five seconds

[nambuccaheadsau]

Installed Trim Enabler on old backup late 2013 i7. Asked to restart to finalise install, rebooterd and illuminated Apple icon came up,no loading bar. Left for an hour or so, no improvement, so powered off using on/off switch, restarted and screen stays black on single beep every five seconds. No joy with powering off and disconnecting from mains overnight.

No recovery or boot from back up external drives, all memory removed, replaced original modules, and then additional sticks with no change. What next one wonders?

 

[steve1960]

Well 5 bleeps does indicate memory not found. If you have changed the memory with known good ones and seated them properly it may point to a logic board fault.

 

[glenthompson]

Did you try with just the original memory and nothing else connected?

 

[nambuccaheadsau]

Thanks guys.

Yes I did. On/off switch works and starts off single beep every five seconds which would be doubtful if logic board?

 

[DeltaMac]

Just to test - remove ALL memory. Try to power up.
Still the same "one beep every 5 seconds"?
Put one (1) memory stick in any slot - try power again.
If no change, move that stick to another slot - try again.
Try each slot with that same stick.
Try again with another memory stick (still only one stick)
If you get no response (always the same beep every 5 seconds), then no memory is recognized.

I think it is a bit strange that you were only installing some software, and not doing anything with hardware when this started (?) -- but, it really sounds like the memory slots have failed, the memory controller died, I expect.

Just one suggestion - a dead backup battery CAN cause unusual symptoms. I don't know if that would include the loss of all memory slots - but might be worth the try to replace the button battery inside your iMac.
After that, repair gets expensive (logic board)

 

[nambuccaheadsau]

Strange to me also but will follow your suggestion and advise in due course.

 

[kinghuang]

Installed Trim Enabler on old backup late 2013 i7. Asked to restart to finalise install, rebooterd and illuminated Apple icon came up,no loading bar. Left for an hour or so, no improvement, so powered off using on/off switch, restarted and screen stays black on single beep every five seconds. No joy with powering off and disconnecting from mains overnight.

No recovery or boot from back up external drives, all memory removed, replaced original modules, and then additional sticks with no change. What next one wonders?

According to https://support.apple.com/en-us/HT202768, one beep every five seconds means “Your Mac isn't detecting any memory (RAM).”

 

[nambuccaheadsau]

Thanks guys. Boot up, no memory installed, blak screen one single beep every five seconds. One module in one slot. boot, same. Other three modules one at a time in each slot, reboot, same each and every time so I agree with the failed memory controller on the logic board.

Have packed it up and will consider coin battery 2032 replacement later. My local Apple Reseller advised iMac repairs cost $69 for a diagnosis only and one can rely on a grand for logic board, graphics etc. Did want the old girl to last until M1's are released but I have a MBP to see me through fortunately.