Late 2012 iMac (A1418) "No RAM Installed" beep

[martinav]

Okay,

I replaced nearly everything in this imac. Logic board and CPU. I removed the RAM, and tested it. It tested good. The only thing left is the power supply. Is this even an option for these symptoms?

Thank you.

 

[krs]

How did you test the RAM?

Did this RAM ever work in this iMac?

Years ago there was the odd RAM that was not compatible with the Mac even though on the surface it met the basic required specs that is normally published.

 

[pm-r]

Gads, where to start with a reply...!!!

First off, is the RAM thoroughly seated. Pull it back out, and reinstall it and use an implement to push it into place if needed as it can take a fair bit of force. Reinserting it will also help clean off any contacts.

Were you getting three chimes/tones at boot time??? That would be an indication of bad RAM or no RAM.


BTW: What was the original problem to cause the replacement of the logic board and reinstalling Ram etc???



- Patrick
======

 

[chscag]

Welcome to our forums.

The replacement logic board and CPU..... were they exact replacements? And is the iMac doing anything at all? Screen lighting up? Fans turned on?

How about the memory modules, are they exactly what a Late 2012 iMac calls for?

*************

Built-in Memory 8 or 16 GB PC3-12800 (1600 MHz) DDR3

Maximum Memory 16 GB

Memory Slots 2 - 204-pin PC3-12800 (1600 MHz) DDR3 SO-DIMM (Non user-accessible)

*************

Take note that the memory modules on this model are not accessible unless the machine is taken apart.

And by the way, a better description would be: A Late 2012 iMac 21.5" model A1418.

 

[krs]

Gads, where to start with a reply...!!!

First off, is the RAM thoroughly seated. Pull it back out, and reinstall it and use an implement to push it into place if needed as it can take a fair bit of force. Reinserting it will also help clean off any contacts.

Very good point!
When I upgraded the RAM on my last Mini, I had to push so hard to get it to seat properly that I thought I was going to break something.

 

[pm-r]

Take note that the memory modules on this model are not accessible unless the machine is taken apart.

I forgot and didn't bother checking on that detail. Nevertheless, any RAM that has been disturbed needs to be checked and confirmed that it is solidly seated.

And with "Logic board and CPU" replacement, it sounds like it has had some serious surgery for whatever the original reason was.


- Patrick
======

 

[chscag]

I believe ifixit has or had instructions on how to upgrade the memory on that model but it's quite involved. Since he changed out the logic board and CPU it leads me to believe that something could be installed wrong or incorrect parts were substituted.

Yeah, that's a lot of surgery for a Mac that's going on 7 years old.

 

[pm-r]

Yeah, that's a lot of surgery for a Mac that's going on 7 years old.

Gee, that sounds similar to some Mac user I know that went through some serious surgeries in his 70s!!! But still surviving at 78 this year!!

I guess it's all sort of being relative.


- Patrick
======

 

[chscag]

But still surviving at 78 this year!!

You know that old saying Patrick... "Keep on trucking"

Or, maybe you're like that Timex commercial: "Takes a licking but keeps on ticking".

 

[chscag]

@martinav:

Please do not double post or start another thread of the same subject. We combined your latest post with the original thread you started.

Thanks.

 

[martinav]

Ok, let me clarify a bit.

Initial issue:

Stock Late 2012 iMac 21.5". It was working fine, then one day, I get the "No RAM Installed" beep code. (1 beep, 5 second silence, repeat)

With the screen removed, logic board lights #1 & #2 illuminate, then beep codes begin. Main cooling fan spins up. Nothing in display, apparently not even backlight.

Attempts to fix:

Phase 1:
I removed one stick of ram. Issue remained.
I removed 2nd stick, replaced it with the first stick. Issue remained.
I installed RAM into a PC, ran MemTest86+. 30 min deep test revealed no errors.

Phase 2:
I got a used logic board from ebay. Decided to replace the CPU with an i7-3770S while I was at it. May as well.
Installed the new logic board with new CPU. Surgery was not all that bad. Much easier than many ultrabooks I have replaced screens and such.
Issue remained.

Phase 3:
I installed new RAM. Crucial CT8G3S160BM. 8GB DDR3L-1600. Issue remained.
Removed one of the sticks. Issue remained.

Phase 4:
I replaced the power supply. Issue remained.
Removed Hard drive and installed a new blank one. Issue remained.

So, I have basically replaced everything but the case and screen. I'm not going any further. Either I get it working with what I have, or I bail and return most of what I have purchased.

Worthy of note, the original i5-3550s cpu was installed in a PC, and works fine.

At this point, the only thing that makes logical sense is that the logic board I purchased used was also faulty in the same manner. It also boots with only two of the indicator lights lit, and goes into the same tone code.

What I know, or am 90% sure of:

1. All the RAM I have is good. Both the original, and the New Crucial RAM.
2. The power supply must be good. Light #1 on the logic board indicates power supply is functioning. Changing it did not provide any different behavior. Plus, the issue did not put the power supply in suspect, but it was cheap(er) so I went ahead and replaced it just to rule it out.

Any other ideas?