Hi guys - I can understand how frustrating the optical drive failing for no specific reason is. Earlier this year the laser failed on me - took one game out after it playing flawlessly, put another in and nothing. After a bit of research on the net I decided it was the laser and not an issue with the drive controller board or motor etc.
It's surprisingly easy to switch out the laser, even more so if you switch out the laser already fitted to a brand new mounting block (the metal chassis thing which i can't remember the name of). It's basically undo some screws on the ps3 case, undo a clip, pull out the blu ray drive, undo a few more screws, unclip a couple more cables pull out the old metal chassis with the laser in it, put in the new one and then reverse the process. Getting the drive back together can be a bit of a pain but i figured it was difficult to truly break it.
20 mins later i've got a blu ray drive that's working perfectly again for all dvd, dvd games, cds, blu ray movies and ps3 games and it's been fine for months now.
the unit cost me about £55 including shipping from China - that was fora kes/kem 400 unit - the ones that go in the 60gb and 20gb versions. The ones for the 40gb and 80gb which have 2 laser diodes in them can be picked up for a bit cheaper.
I would say that you're probably better off getting from a UK source and if you can buy from someone which gives you at least a months warranty. I had one from China which had a 'white ribbon clip' (google it for more info) and it lasted all of 5 seconds reading a cd then it died. It was a long wait for the return / replacement.
here's some links from ebay
20gb/60gb laser with the metal chassis - single diode - uk seller - 2 months warranty:
New SONY PS3 LASER KEM-400AAA /KES-400AAA with DECK UK on eBay (end time 26-Nov-09 16:35:20 GMT)
20gb/60gb laser - no metal chassis - single diode - uk seller - 2 months warranty
Playstation 3 - PS3 - KES-400AAA LASER NEW UK SELLER! on eBay (end time 28-Nov-09 16:30:40 GMT)
Whilst it's a £10 difference i'd reccomend getting the metal chassis if you've not swapped out lasers before since it saves you having to get the grease for the guides the laser runs across - it's also just a little bit less fiddly.
for 40gb / 80gb - laser with metal chassis - uk seller - 2 months warranty
SONY PS3 Laser Lens KEM-410ACA with Carriage NEW UK on eBay (end time 26-Nov-09 16:49:00 GMT)
Strangely - back at the beginning of the year when i was needing a new laser, 20/60gb single diode ones were in short supply and UK sellers were charging around £75 for a laser alone - also ebay was flooded with 410's which were around £40.
If you've replaced any previous console lasers e.g. ps2, xbox, gamecube then this should be a piece of cake for you and hopefully save you a bit of money. Of course only do this after contacting Sony and ensuring they won't give you a refurbished console - the last thing you want is to replace a laser at £50 and then get YLOD - I didn't have much choice since mine's a JPN machine.
anyway - i hope it helps, - BTW the links above that i've posted isn't a link to a personal business or anything - just seems that there's only 1 guy on ebay right now offering a warranty - there was another company from london earlier this year that was offering a 90day warranty or something so if you're not desperate maybe keep an eye out for that and see if it pops up with a better price.