update 3: i managed to revive the lamp, during autopsy, i noted some bad soldering on the wire that connect one led module.
now it works!  

Did you managed to make some photos of the inside?

Did you managed to make some photos of the inside?

no, bad soldering was only in led assembly and not ballast, so i didn't took all lamp apart; the photos are similar to which are on lamptech.
however, my lamp have only 3 blue leds for "leaf" instead 6 cited on the site.
During repairing, i've noted an well made lamp: strong clips to keep the leaf closed and thermal sheet to aid thermal dissipation on ceramic led assembly.

I see...

For the number of chips: From the time the lamp was introduced, new LED devices arrived being more than twice the power rating, therefore fewer of them suffice for the same power per leaf.
It seems, the industry is still searching the best optimum power per device: It started with 1W, then went up to 3W per die, then went down back to ~100mW per die, now again going uo through 200mW till 500mW per die...

I would guess all that is related to the crystal defect density on the wafers (the defects are of atomic size, but when they reach an active area of the device, that device is not working, so larger devices, higher the chance it would be affected by some defect):
They started with quite large chips, but the high defect density at that time made quite high scrap rate, so relatively few good chips had to pay the complete wafer production.
Then moving to small chips smaller parts become rejected, so the scrap rate become low. But as the individual dies were small, quite large area was wasted by their inactive perimeter structure (if the active structure reach the sawing place, it will become not working, so dedicated inactive empty space have to be kept on the wafer for the consequent sawing).
Now when the defect density became lower, it allows to use larger dies, so less space wasted for the perimeter structures, yet without too high scrap rate due to some defect affecting the die.

interesting!

however, if you need to open this lamp, first you need to remove upper cap (philips printed plastic), then you can remove remote phospor via an small screwdriver and then, you can remove led assembly by taking out the screws and pulling up the assembly.

now i'm using the lamp Philips kindly sent me as replacement, it is an small size E27 lamp and, because is more directional than master led, i prefere it, because it light my table much more than the L-prize lamp.
it get quite warm, but remain an comfortable warm.

updated with recent failures... 
and recent new lamps 

However, what do you think about this lamp?

http://www.ikea.com/it/it/catalog/products/40317139/

It's rated 20lm