Electronics > Repair
Replacing DDR3 memory chips
(1/1)
ealex:
Hello

I'm trying to fix an asus ux31e ultrabook that shows a lot of RAM errors.
The fault happens exactly after the 2GB mark, and then the faulting addresses follow a base-2 pattern.

By the looks of it either one or more of the DRAM chips have broken solder balls, or at leas one of them is faulty.
Worst case - the CPU itself has a bad solder joint, and that's way out of my expertise and available tools.
I assume it's a mechanical problem because the keyboard is very unresponsive and requires quite a lot of pressure to register any key press.
I've got it for free, so worst case I still get a very nice LCD for witch I can find external driver board, a good SSD and some LiPo cells.

The plan is to first try and reflow all 8 of the ram chips: apply some good flux and re-melt the solder.
If that fails I might try getting a new set of RAM chips - or maybe I can try it "rossman style" and rebuild the balls with leaded solder and a lot of flux.
I can play with it as long as I don't damage the board.

The motherboard uses 8 Elpida EDJ4216BASE-DJ-F chips: https://www.alldatasheet.com/datasheet-pdf/view/458060/ELPIDA/EDJ4216BASE-DJ-F.html
Those are no longer available at mouser / farnell (only on aliexpress and at a high price).
I think the closest ones are AS4C256M16D3C-12BCN available at mouser: https://ro.mouser.com/datasheet/2/12/AllianceMemory_4G_DDR3_AS4C256M16D3C_May2020_Rev1_-2301319.pdf
The main difference seems to be the DQUx / DQLx pins placement - all other signals seems to match.
Are there any other parameters I should be aware of ? the replacement chip seems faster than the original one : DDR3-1666 versus DDR3-1333

(I think I should add an extra layer of aluminium foil on the side with the cpu / chipset to protect it as much as possible)

Thanks,
Alexandru

Navigation
Message Index
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod