Il semblerait qu'après seulement quelques jours de developpé Monsieur mph, un français, nous ait pondu un downgrader fonctionnel. Voilà une copie de son post :

Citation:
Download at :

http://rapidshare.de/files/5607151/MPHDowngrader.zip.html


-> This is has been tested by me Wink I AM NOT RESPONSABLE FOR EVENTUALS DAMAGES 1.50 method
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Requires :
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- PSP 2.00 (if you have an 1.51 or 1.52, update to 2.00)
- The 1.50 EBOOT.PBP update (http://shockzone.free.fr/PSP/Tool/EBOOT_1.50.zip)
- MPHDowngrader (http://rapidshare.de/files/5607151/MPHDowngrader.zip.html)



Installation :
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- Create a UPDATE folder in PSP/GAME/ folder of your memory stick
- Copy EBOOT.PBP (update 1.50) in UPDATE folder
- Unpack MPHDowngrader.zip
- Copy overflow.tif in your PSP/PHOTO/ folder of your memory stick
- Copy h.bin in root of your memory stick
- Copy index.dat in root of your memory stick
- Plug the AC adaptor


Then, enter in VSHELL PHOTO MENU, this will launch Version Changer.

Create an USB connection and if the Version Changer has been installed, a new file is created in your root of your memory stick (ms0:/index.dat.bak).

Then go to VSHELL GAME MENU and launch 1.50 update.

Follow the instructions ...


The installation will stop at 99% but it's normal, continue follow the instruction

MPH

Edit :
Source : http://www.psphacks.net/forums/viewtopic.php?t=6963&start=0&postdays=0&postorder=asc&highlight=