Tuesday, February 9, 2010

Need a fried hard drive?

Did you ever fry a hard drive? I did one a few weeks ago and learnt an important lesson. It was a small issue and hardly worth noting but it did cost me a hard disk(in replacement). Here's what happened.

I do part time computer technician's job and here's something I had to deal with, a few weeks ago. I got a call for a computer repair and I went to their home to check it out. It was a case of non booting computer. It was a 6 month old Pentium 4 based computer (didn't understand why someone would buy that in the age of dual and quad cores). The problem was, it would not give any signs of life. As you must have already guessed, it was a case of power supply unit (PSU) gone bad. It's a common thing with most people who do not use UPS and use the (cheap and sub-standard) psu that comes along with a cheap cabinet. Getting a good and reliable psu is very important but we will speak about it in another post.

I checked the psu with my digital multi-meter(DMM) and confirmed that it was dead. I explained it to my customer and he asked me to replace the dead psu. I replaced it immediately and then the computer was working fine. I always carry an extra psu other than the one I use for testing purposes because problems like these are very common in this place. There were few other problems with their Windows and after a few minutes work, it was all fine and healthy. It was time for me to leave and I demanded my fee which was the psu's price + Rs 20(a little less than half a dollar). I charge less because I do this work for pleasure. The man was highly impressed with the neat work and was actually shocked when he learned about my small fee (others in the area charge around Rs 500). He paid me out and I was ready to leave when he called me back and asked me why the side fan of the cabinet was not working. I had forgotten to power the case's fans. I opened up the case, but there wasn't any free molex (power) connector available. So I removed the one connected to the (ide)hard disk(as it was the nearest) and connected it to the fans, and from there took the other one(fans usually have male and female molex in Y formation) and connected it back to the hard disk and shut the case back.

I powered on the computer and this time it gave an error while booting and won't go ahead. It said 'system disk error, press any key to restart.'  I restarted the computer but it was the problems again. I checked the BIOS settings for boot priority and they were all right. Suddenly I noticed the BIOS main screen and saw that it didn't detect the hard disk. I thought I might not have connected it to the hard disk properly after I removed the connection so I opened the case again and tightened the molex on the hard disk. Powered on the computer again but it still wasn't detecting the hard disk yet and I got worried. The man was standing beside me and seeing while I was working and he seemed to notice the worry on my face. I suddenly realised what mistake I might have (I did actually!) made.

I opened up the case again and poked my nose near the hard disk bays and sure it smelled of burnt electronics. I had fried the hard disk! I managed to make a fool out of myself in front of my customer. I acknowledged my mistake, went back to my room and got back with a replacement. I removed the molex from the bad hard disk and replaced this good one in its place. Just to check what had made the hard disk circuit to burn, I checked the power connector attached to the hard disk and there was the culprit. On closer observation, I noticed that the 4 pins of this male molex connector(coming from the Y of side fan) was crooked and therefore even though I thought I had fit the connector snugly, it didn't actually go in properly and might just be touching the other side pin which had caused a short circuiting. I finished with the replacement, loaded up Windows and left the place. I was lucky that the person did not have any important files on his computer. He used it to watch movies and listen to songs.

I went back home and analysed the situation more clearly. There could have been two reasons for the hard disk circuit to get fried. One was, as I mentioned, that it might have touched the other pin from inside when I tried to force the connector in and that may have resulted in outright short circuiting. As for the other reason, I researched a bit on it and found out the obvious but often ignored fact. As we know, all wires and connecting parts have some amount of electrical resistance to them. If the connection is loosely fit, then it creates a gap between the two connections and this results in greatly increased resistance. As the resistance increases, so does the heat and this may have spoilt the hard disk. That is why, it's important to make sure that all the connectors from the psu are set firmly and not left loose. This is the same (arguable) reason why modular power supply units are not preferred over wired ones.
So I learned from my mistake and always make it a thing to check if all the power connectors are properly fit. I hope this was some good information to you all. Will post more if I find something worth sharing.

If you face computer heating issues or face sudden shutdowns, then check this post here

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