BGman wrote:
Hi Old Tech,
Take my advice - don't touch the PCBA! The problem is not there. There are 3 posibilities:
1. A broken head
2. Defective commutator/preamp (inside the HDA)
3. Critical module of SA is not readable
You can do nothing about the first two of them. A specialist can help you in the third case, but for you it will be wasting of too much time.
Good like.
Hi...and thanks for responding. Your suggestions gave me something to think about.
Please don't take anything I say as a personal attack on you because it certainly is not intended as such. But I'm getting a bit frustrated with this "don't touch' the innards of the hard drive.
I pointed out that I'm an electronics tech with many years experience in electronics and computers. That's what techs do, we repair things. I used to take hard drives apart on customer premises, change the heads and/or platters, and they worked fine. I also pointed out that things have changed. Todays drives have a much higher density of cylinders per inch.
A similar fetish developed around static electricity. I have never worn an anti-static strap and I have never blown a device. I don't trust anti-static devices because they have a high resistance built into them that supposedly limits static current. It doesn't work that way. You'd need copper wire wrapped around your wrist and I'm not about to do that. I have found it is enough to ground yourself to grounded metal 'each' time you move around.
There is a folklore developing in the hard drive community about dust. It has gotten to be a fetish. It's not new to me, however, since I've been hearing about the mysterious dangers of dust most of my life. What the heck is that stuff anyway? We should be using it as a secret weapon.
A quick story. I took a hard drive to pieces on a customer's premises many years ago. I exposed the platter and heads to flour and general grain dust, because the customer's business was bakery goods. I did the same on another customer's premises who used a very clean room with air filters and everything else. Guess whose drive failed?
Do you want to know why? The computer operator in the clean room was a smoker. She smoked while entering data, right in the clean room. The particles from the cigarette is dust, with lots of sticky stuff in it like tar and the metal products the cigarette manufacturers add to affect the taste of the cigarette. Even though the hard drive had it's own filters, the goo from the cigarette had gotten through them and stuck to the heads.
Dust is not composed of one thing. If it has an organic base, say from cigarette smoke, or dandruff and skin matter, then it 'might' pose a risk. There is an article on this site by Stanislav Korb. It's an excellent article on how to change the entire head stack. I followed the article with great interest because it's the first article I've read that tackles modern hard drives. It also confirmed my suspicion that nothing has changed, even though modern drives are much more intricate. If you're careful, use 99% isopropyl alcohol (it 'must' be 99%) to clean up, use lint-free swabs of some kind, and work in a relatively clean atmosphere, it can be done.
Consider the aerodynamics of a flying HDD head. It is held above the disk surface only by the air pressure under it created by the high speed of the drive. That's why Stanislav suggest rotating the platters as you remove the heads, because there is so much relative pressure on them that dragging them forceably across the platters will scratch the surface. I think Stanislav even suggested wedging the heads apart slightly to ease them out.
Anyway, with the disk turning at 7200 RPM, which is double the speed they turned in my day, the heads maintain a relative distance above the surface. I say relative because the heads are prone to vibration and they will wobble up and down as they fly. If they hit a piece of organic matter, they will fly right through it, but the jolt will cause the head to oscillate in it's path. "If' it hits the surface, it's probably game over. The greatest danger there is that the smear caused by the collision will affect the heads ability to read and write. I'm sure that a lot of the problems attributed to opening the head chamber is contamination of the heads themselves by matter. You need to find a way to clean them.
With tars like those from cigarettes, the tar will actually stick to the heads. I've seen the trail left by such a head and the smearing on the head surface. It doesn't take much to ground the head. With other types of dust, like lint, it's hard to say what will happen. I'm trying to say that heads and platters are a lot tougher than people seem to think. In my case, I'm not aiming to put the drive back into use, I just want to recover some data and chuck it. I feel strongly that I have a decent chance of accomplishing that.
You mentioned there was nothing to be done about changing the preamp. Why? The problem I'm having is locating parts. Surface mount technology is admittedly tougher to work on, but there are techniques available to all of us to change even that preamp. The first thing you need is a high powered magnifier. I have terminated lots of fibre optic cable which is a lot smaller than the preamp. I used a 100 times magnifier to see the end of the fibre because it needs to be perpendicular to the length.
The next thing you need is a really good soldering station, with a very fine tip, and high quality, fine tweezers. I can see from the ribbon cable attached to the heads that heat will be a problem. That means careful control of tip temperature and heat sinking. I am not pretending it will be easy, but I can't accept your advice that nothing can be done. At the same time, you have helped a lot by prompting me to consider looking elsewhere first. In my still-primitive approach, I am considering ways to bypass the manufacturer's control over the voice coil mechanism. I have a lot more reading to do.
With respect to the experts you mentioned, the only way to gain expertise is to research, ask questions, and 'do it'. If you fail, big deal, at least you tried.