WD U12 swap - my experiment

[Nick_CT]

I've only become interested in DR in the last few months and have been doing lots of reading and research. I've since been collecting spare HDDs to practice on and upskill. I've been in IT support my whole life.

I got 2 WD 40GB drives in working condition, both with matching/identical PCB versions. I wanted to try and swap PCBs to see first hand how it wouldn't work without swapping the U12 as well. I swapped the PCBS and as predicted it didn't work, they picked up as weird models, wouldn't initialise etc.

In theory I should have been able to swap the U12 chips and both drives should both start working again with each others PCBs. I got out the heat gun and carefully removed the U12's on each PCB and swapped them over. I powered up the first drive and bingo, worked like a charm. All the data was there, perfect.

Powered up the second drive and it made some noises that I never knew a drive could make - horrific noises. I quickly powered it down seeing that it was obviously not very happy. I could only think that I had either damaged the donor U12 or something on the PCB. I heated it up, removed it and placed it again, taking care to make sure it was spot on. Powered up the drive and bingo - worked like a dream. I obviously did a poor resoldering job first time around.

I set the heat gun so that it was just hot enough to melt the solder. I was wondering if anyone had experiences where the heat had damaged the components on the PCB? It's obvious that the components can take a lot of heat, but how much until you cause damage? Hopefully I won't have to figure that out first hand.

Either way I'm chuffed that my first U12 swap actually worked. It's a step in the right direction.

[drc]

Sure, take a spare/dead PCB and hit it with the heat gun... shouldn't take too long before the PCB layers start splitting

[ppumkin]

PCB surface not only problem. Many pcbs are multi layered- Heating up can cause unwanted effects inside the PCB itself.
You can buy heat resistant adhesive tape and mask off the areas around the place you want to do it.

But in a previous post - I said heat guns are old school and they do head in.
Then somebody posted something about a oven with grill method "and pizza left overs haha"

I recommend you use quickChip!
http://www.youtube.com/watch?v=jaarYY2Lxiw

I have no idea who sells it in SA- but if you need some pm me.

[drc]

Chipquik is good for desoldering but not for resoldering... unless you like chips falling off your PCB at 135 deg F

[ppumkin]

drc makes a valid point.

I did not state that because its obvious to me not to use chip quick to resolder.
Please watch this.

http://www.youtube.com/watch?v=erb6-i54tbo

Notice that the pcb area where he is "sodering" is flooded with liquid flux. This prevents joints between pins. It needs some practice to get to that level. He is also using a higher temperature resistant solder like drc mentioned.

Good Luck

[HDD Spaz]

my old trusty heat gun has never let me down.

[Nick_CT]

I had a look at the Chipquick videoes etc, looks like interesting and useful stuff. I can see how the solution can become a problem though, as in it's great for desoldering but if your chips are going to fall off later on at such a low temperature that's not great. I've had a look and it doesn't seem to be available in SA - would like to try some though. Will PM you pumkin.

So far the heat gun has worked ok on a few jobs and got the drives back up and running. I'll have to experiment to see at what point it does more harm than good.

[Nick_CT]

Just did another U12 swap with the heat gun. Worked without any problems - seems to be working for me so far.