My computer is used every day
and I was pretty sure it was taking longer and longer to boot
up. Other ominous signs were also cropping up. When I bothered
to check the Windows logs I usually found red marks. These were
always uninformative although the type of error was often repeated.
Typical was an iastor error.Searching the Internet for explanations
of the error number, the phrase that kept appearing or a file
name was never definitive and far from clear.
What else happened? Just once or twice
a fortnight the computer jammed up. The desktop was present and
the mouse moved around, but opening a program often resulted
in "not responding" being appended to the information
on the screen.
Back to the latest problem. A drive
had been lost and Intel provided me with its identity. It was
the drive connected to Port 1 and its serial number was S1D8HA5T.
What should I do? Well, ideally I'd have got a spare drive, either
running inside the computer or tucked away in a handy box. I
didn't have either so I perused the catalogues and promptly ordered
a new drive. At this point I considered a switch from mechanical
drives to solid state, but there are good reasons for not taking
that option. Primarily, the computer is at risk now that it's
lost its mirror, so venturing into a totally different setup
was risky. Maybe later when things are back to normal?
A note about selecting a new hard drive in a RAID setup. A replacement hard drive has to have a capacity equal or greater than the remaining good drive. There is a way round this. So, for example if I wished to fit a pair of solid state drives having a capacity of say 240GB I would first need to reduce Drive C active partition to this figure or slightly less in practice. The requirement is to determine exactly what the 240GB capacity really is, then to use the Windows shrink feature to turn my 1T hard drive into a 240GB hard drive. The mirror can then be removed and a new 240GB SSD added. This is then used to mirror the shrunk 1T Drive C. When the rebuild has finished the shrunk 1T drive is unplugged and a second 240GB drive is fitted and set to mirror the first SSD. To do all this you need a clear head and to not make any mistakes!
A friend brought me a pair of external hard drives. They are 500GByte and 1.5TByte and carry zillions of backup pictures and files from now defunct computers so are pretty important to him.
He said he'd mislaid the power supplies for the pair of external hard drives so used an alternative power supply instead and failed to get either working. Now, if the drives have an internally stabilized supply he'll be OK, but if they need a 12 volt stabilized supply he might be in trouble. I opened the first case and removed the SATA drive then plugged it into my computer. Oops.. I shouldn't have done that as the computer just coughed and died. I unplugged the offending drive and found the computer wouldn't boot up. After switching the mains lead for another it suddenly came back on. I turned it off and tried the original lead again. This time it worked OK. Very odd.
I checked the hard drive and found the 12 volt pins were shorted to the ground pins. A protection diode had failed short-circuit. I removed the diode and the drive worked OK. This one is made by Seagate and the diode was quite visible, but there's no fuse so the design is not so good. I removed the second drive from its housing and measured the resistance across the 12 volt input to ground. No short so I plugged it into my test computer. It went unrecognised but it was spinning. As this Samsung drive has a featureless circuit board the components are hidden underneath so I removed six torx screws and looked underneath.
A layer of padding was stuck to the components. It was stuck because a protection diode had got very hot and melted the plastic padding which had stuck to it.
It looked a sorry state. Lots of soot and vaporised copper. However, not altogether bad news as the protection diode had failed short circuit and blown some tracks which I guess were designed to fuse open. After cleaning up the soot I removed the diode and added a short length of wire to replace the missing tracks. I screwed back the circuit board and tried out the drive. Success, we now have two working drives.
The diodes are coded with "LG" and "KVP", both of which mean they are TVS protection diodes rated at 13 volts. These can tolerate lots of power and clamp too high a voltage on the 12 volt input, but not indefinitely. The power supplies are rated at around 2 Amps which generally means their output voltage will be 12 volts at the rated output current. Because the output circuit will have some inherent resistance, lets say 6 ohms, the output at 1 Amp might be as high as 14 volts, hence the failure of the diodes.