Why the 821-1480 and 821-2049 Hard Drive Cables Die

[iambehr]

Hello,

I know there has been a lot of speculation about the frequent failures of these hard drive cables. I have heard from a couple of sources that the machined finish of the macbook interior abrades the cable and causes shorts that can be insulated with electrical or kapton tape.

I'd like to put forward my theory:

I have dissected several of these, and I can't see any visible signs of abrasion or piercing of the insulation. Instead, what I have seen is, after scraping the insulation in several points ( before, after, and between the sections of the flex cable that are bent) I can probe with the multimeter and there is a disconnect. After carefully melting the insulation off on the bends, I can see that there are often breaks or stress fractures where the cable is close to a 90 degree bend.

My theory is that because of the bends pre stressing the copper traces, when the cable is flexed under normal movement (the bottom case pushing in, especially around the bottom of the dvd drive)and extreme movement (dropping it) the copper "work hardens" and may begin to crack.

My solution when installing a new hard drive cable is this: taping or otherwise securing the cable where it is loose to avoid excess movement, "padding" the sharp bends where the cable is in close proximity to the case with kapton or other tape, and very carefully bending new cables so that they are not bent at a sharp right angle, but still fit normally.

Let me know what you think,

Thanks,

Stefan

 

[dukefawks]

The copper traces are cold deformed and stretched making them prone to cracking. I just slap in a new one and whatever they never return usually. Heat treating them to relieve the stress in the copper may also help.

 

[iambehr]

Yeah,

I was thinking something along those lines. Copper gets very brittle. I rarely have HD cables return.

I have noticed that failure rates for (presumably) old part # 821-1480 are much higher than the 821-2049 (suspected newer part number to correct issue). Maybe apple attempted to correct the issue.

 

[Joesipaq]

I am going to bump this topic back alive. I might have missed another post similar - but I wanted to know, what is the best replacement cable to use when swapping a dead 821-1480 out. I remember once Luis mentioning the "so and so year model cables never have an issue and can replace these" in a YT video, but which video - no idea.

 

[dukefawks]

821-2049 is the revised/improved version but it still dies. I just slap in there whatever I have in the pile.

 

[Inwerp]

vibration + sandpaper-like aluminum case + pressure from HDD + 40-50°С = short circuit, slowly burns dataline or +5v.
i repaired 4 devices with this issue a few years ago, no one returned.
you either install SSD or put insulation tape under the cable, that's it.
there are thousands of different notebooks with more than 90 degrees bends. almost every PC laptop has full 180 bends on keyboard cable and it usually works much longer than Apple SATA snowflake. bending simply does not compute.

 

[Inwerp]

No Title

So i finally got my hands on this shitty SATA cable. I removed the insulation tape with a heat gun and well... it looks like the whole cable is made from pure copper which probably half-breaks the moment apple bends it for the very first time.

 

[Inwerp]

i was completely wrong, this post is a complete BS, See photos just below )

 

[dukefawks]

No it is a metallurgical problem. Copper that is cold deformed has internal stress in it and without annealing it it will in some cases start to crack to releive the stresses. Copper/brass are very prone to this problem and it is known. It is also referred to as stress-corrosion, common anywhere where copper is bend without annealing it.

 

[Inwerp]

Do you think it makes sense to heat the cable before bending? I guess PVC can handle 100-120°C, but would it be enough to make it more ductile?

 

[dukefawks]

Heat it after bending to anneal it. But whatever just put a new cable in it and just be happy. Change it again after a year and make money again