Chosen Solution
A service person looked at the computer and found it full of lint. His diagnosis is a burned logic board. I was given the computer and ordered from iFixit.com – a 1.8 GHz logic board, an I/O board, and a new battery–hoping to give myself a virtually new computer at half price. After cleaning the machine and replacing all three parts above I turned it on and the chime repeated itself and a blank screen presented itself the same as the original complaint. Now what? 1) “New” logic board from iFixit was used and tested, of course. Is it possible to have a repeat problem? 2) Could it be the memory board is the problem? (The only thing not replaced.) 3) I have researched the repeating chime problem from several sites and tried every suggestion all to no avail. It seems there is obviously a hardware problem, but hard for me to accept the “new” logic board that was tested is the problem. Help!
From a second Mac create a bootable OS installer thumb drive following this guide: How to create a bootable macOS Sierra installer drive. Then see if your system will boot up under it. You’ll need to hold the Option key just when you hear the Bong so you can gain access to the drive manager to select the external drive. Once their, run Disk Utility to check your drive. If you have a backup delete the partition and re-install the OS. Let us know how it goes! Update (03/27/2017) is there a pattern in the sound? Here’s a good Apple T/N writeup on the different startup sounds and the basic causes: About Mac startup tones.
Try clearing the PRAM - not once but THREE times in succession. If this doesn’t cure the fault, then I reckon you have a stuck key on the keyboard.
