Fantastic, or not - as the case may be

Background. Some time back I spent a small number of years repairing electronic comms kit. I used to turn around UHF transceivers in less than ten minutes, repaired and ready for use. I learned a lot about diagnostics. Including the fact that if you can't find the problem within a relatively short time (proportionate to your knowledge of the kit in question), then it's more productive to put it aside and come back to it.

The problem. Some months back I noticed that my main machine was making a noise for the first few minutes on switch on. Thereafter it was quite. I'd investigated, but since it wasn't loud, irritating or obvious - I left it. Last week the noise grew progressively worse, to a point where it was annoying and potentially could/would cause secondary damage IMHO. I'd sort of concluded it was most likely a cooling fan. It had that loose bearing sound about it. My concerns related to over temperature issues. Over an hour or so I slowly disconnected all the fans readily reachable (6 in total). I concluded it was the CPU fan, by elimination. I ordered a replacement, feeling hopeful. it arrived Friday and I left the machine switched off for two days. I refuse to admit to withdrawal symptoms. Friday I fitted the new fan. Ok, I totally stripped the machine, withdrew the motherboard, unscrewed the frame, worked out how to fit the fan frame to the board frame (one of those 'easy when you know how' jobs), then fitted it all back together again. On cabling up I switched on, duly noted the fancy blue led (yippee), then sadly noted that the noise was still present. I went into critical diagnostics mode. Disconnected everything except the motherboard and listened. Yet again I started it with a screwdriver inserted into each fan to stop it. Yet again the noise was not sourced from any of the fans! I stared at the chassis for ten minutes working logically through the components. By chance I tipped the chassis up and there, nestling between the graphics card and the soundblaster (on the graphics card), was a fan! About 1.5" square, half an inch thick, and when I touched it, yes, the noise stopped. Grrrr.

I cleaned it up (absolutely filthy) but the damage was done. It now quietens down after an hour or so but can no longer be trusted to do its job. A new card on order and a salutory lesson in diagnostics, fitting heatsinks and the frightening rate of change of graphics card fitments! I'm now looking at my 4 year old system and wondering how much longer before I should replace it.