820-3023 - 3 beeps / Freezes with Graphical glitches / Power cycling

smiba

New member
Hi everyone!

I have a macbook air here, history unknown but I think someone tried to do something on it before. It looks like someone tried to reflow the memory modules but used a way too low temperature and no flux (The plastic around the modules are slightly molten but not enough to say they used more then 200C). Other then that nothing else seems to be touched

The system sometimes shows the 3 beeps and doesn't boot, sometimes it crashes while playing the chime sound (Which makes for some really loud and scary audio glitches!) or sometimes it just works for 2 to 10 minutes before the video glitches and the system freezes. The freezes do not appear to be temperature related and its just luck if it will keep on working. The system always crashes after a while and crashes faster if the memory is being loaded (memory testing etc.)

The voltage of the memory modules is at a stable 1.500V

I tried reflowing the modules with flux and waited until they floated on the solder before I moved on to the next chip. This only seemed to have made the issues worse and now it crashes way more often, I can usually only get up to 3 minutes or it shows 3 beeps at POST.

My bet is on a bad module somewhere. I currently don't have a lot of devices to work on so I'm alright with replacing the modules if that's what's needed.

So What modules should I buy? I prefer pre-balled or new ones as it would save me on time it takes to ball them.

EDIT: Here are a couple of pictures of when the device froze
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smiba

New member
Yeah I was thinking about the PCH/CPU, but if there are random I/O screw ups the patterns woudn't stay the same.

If video memory gets corrupted in the transfer I'd assume more glitchy-ness but the patterns are always these blocky kind of glitches. Also the video is still and not moving around with random patterns (As more common with I/O disruptions)

Also I've managed to make the issue worse by pointing my hot air at the memory ICs which could show the issue is with one of the chips.
Since the system detects this as "two memory banks", would it be possible to remove one half and see if that does something?

Obviously it says nothing if the CPU is still screwing up the memory, but memtest is able to find issues just in a couple of seconds
Click image for larger version  Name:	IMG_20171001_225934.jpg Views:	1 Size:	151.6 KB ID:	26206

EDIT: Started memtest another time and it failed on exactly the same second, percentage in the same region of memory.
Is there a way of finding out what module is part of this region?
IMG_20171001_231023.jpg
 
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Alan.L

Member
thats a actually good idea, i never thought of removing one of the memory banks permanently.... i'll try on my faulty board. hope this is possible
memtest is passed on my board tho.
 

smiba

New member
Let me know how that works for you!

If memtest passes even after hours your memory is most likely OK though and the PCH is most definitely to blame. But if the board is trashed anyways, it can be a neat experiment :)
 

Alan.L

Member
damn, doesnt work. now full beep all the time. do i need to remove something else
 
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smiba

New member
Did you remove Channel A or Channel B?

I'm not even sure if it supports running with one bank though, maybe apple's programming does not allow this. I think the CPU on its own should be able to POST with only one bank though...
 

smiba

New member
I dont think you can remove the A side, since the system always expects that slot to be loaded.
atleast that's how it used to be on some windows machines so I assume it's a CPU thing
 

smiba

New member
dukefawks Any input or no idea/could be anything? Really sorry to bother but could I in theory remove the B side of the memory?

Much appreciated

EDIT:

Just looked up it and both the 2nd and 3rd generation Intel mobile processors can work in Single Channel mode and this happens when either Slot A or Slot B is populated. So I was wrong earlier and removing Bank A should've done something. So unless apple did something in the firmware to prevent running the system without both banks populated I'm not sure whats up. (Also I think the 3 beeps is too low-level to be easy to re-program by apple? Might even be hardwired)

Alan.L You sure you removed the right modules? Maybe Bank B contains the messed up part?
 
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dukefawks

Administrator
My input is that if you want to change all RAM chips then it will probably work. In my eyes this board is therefor junk.
 

smiba

New member
Alright, I'll put it all the way down on the list in case I have time for it.
Just gotta put on some good music and time will fly :)
 

Alan.L

Member
Alan.L You sure you removed the right modules? Maybe Bank B contains the messed up part?[/QUOTE]

not 100% sure,,.. but OMG i dont want to change 16 rams. 8 is already enough.

i'am waiting for the DDR3-2 stencil to arrive.
 
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