What likely caused this drive to catch fire?
 

What likely caused this drive to catch fire?

http://s21.postimg.org/bgthib2sn/photo.jpg

From the photo you can see a burn mark on the case, the sata plug partially melted, and there are burn marks on the harddrive as well near the pins for the sata plug.

The box would not boot, or even post bios, assuming the PSU went bad after the fire.

There were no other burn marks, I checked the motherboard connectors, a second harddrive, and took apart the power supply.

I'm thinkings it was one of the following:
Bad Drive
Bad PSU
Power Surge
Bad Sata Adapter

Which one would be the most likely cause of this?

TIA

I'm no expert but due to the direction of the flash marks on the HD circuit board (a "V" seemingly originating from the connector) and the burn marks on the SATA power connector I'd say short circuit in said connector?

Good call, I think you're right.

I'd reckon that there was a bad connection; high resistance, should be a short circuit between each connector and pin. The high resistance,(higher than 0 ohms) we're talking only a few ohms, would cause the connector to heat up eventually causing the melting and latterly the scorch marks. I'm assuming the system was left on for long periods or did this happen pretty quickly with a bang?
Does it POST now with the drive disconnected or is it bricked?

Play Bonny!

:hattip:

The box has been powered on continously for about 10 months.

With the drive unplugged it still wouldn't boot, or post, so after the short circuit something went wrong with the power supply as well it seems. I haven't tried the motherboard with a new psu yet.

Very difficult to say. Something bad happened in the vicinity of that connector, but was it the cause or was it an effect? A high current was drawn, but that was presumably an effect of something else.

I'd guess power surge (on the electricity supply) would be unlikely, because whatever happened continued for a matter of quite a few seconds and not milliseconds or microseconds. On the other hand, if the power surge killed the power supply (should be unlikely, but some power supplies are, err, not very good) the power supply might deliver a high voltage (...should be unlikely...) for an extended period.

A power supply blow up is possible, but there might be some evidence in the power supply (but, you'd have difficulty telling cause from effect).

A bad connection in the cable, which would probably have to be a short between something like a short between one of the power supply lines and ground, and the short in either the cable side of the connector or the board-mounted side, would be possible, and should leave some evidence (ie, a fragment of copper that formed the short, or a trail of blackened material).

It is possible that an internal short in the hard drive could cause this kind of fault. It would probably have to be a short between a power supply connection and something else (eg, ground) for enough current to flow to cause this kind of damage.

I did look at the two darkened areas and wondered whether there were tracks on the other side of the board, or internal to the board, that could carry a high current, but I doubt that's right (that would probably be clear if you look at the other side of the board) - it probably is the connector itself, at those two pins, which overheated and which blew out some rubbish and it left that evidence across the board. Looking more closely at the circuit lands/connector receptacles might give you more of a clue.

For example, a screw shorting from the chassis to a power supply track could cause that kind of thing, but evidence of that ought to be very obvious. Well, there'd be that screw, for a start.

There is also some evidence in the mark on the chassis, but it is a bit difficult for us (not for you!) to work out the alignment between the chassis marks and the former alignment of the drive and the connectors.

Most times the PSU goes and takes other things with it. So check the power supply for similar symptoms. You'll likely have to replace the PSU in either case. And unfortnately the drive and the PSU were probably not the only victims of failure / degradation. Possible lightning hit? I don't know, it's hardware, I'm a software guy.

I like to break drives in on an external docking bay. This way if they give off abnormal heat or make more noise than similar drives, I know in advanced before risking it inside a computer. One of my drives gives off extra heat, and closer examination shows dinks in the case. I bought it new OTS, so I can only assume that it came from the factory that way. It still works, But I know to never install that one in a case.

Dust can be a conductor.

A build-up of dust inside the case could well account for the short. Was it dusty?

It is a good practice to inspect vents and, in the case of desktops, heat sinks for dust regularly and keep them clean.