SERVICE MODE DOWNGRADING - 3.55 [OUTDATED]
CONFIRMED NOW WORKING! INSTRUCTIONS BELOW :
3.55 Downgrade has been confirmed on both FAT and SLIM consoles.
Please note you CANNOT use these files if you bought a PS3 that came stock with FW 3.50. DO NOT DO IT. STOP NOW.
THE SAME WARNINGS AND RULES APPLY:
You may want to download geo's 3.55-jb and install that and blackb0x ftp if you have not, it will be very useful for the next bit.
blackb0x FTP server 1.2:
If you have a fat PS3 with 256MB NAND you will need to back up your dev_flash folders, as you WILL LOSE BLURAY PLAYBACK. Please see one of the many threads here at PSX-SCENE detailing how to get your bluray playback re-enabled if you forfeit this step. (on my FAT model i restored the DRL1 and DRL2 files in del_flash(2?) I did get to however keep all of my signed 3.55-jb homebrew, and it all works in retail mode except of course backup managers)
If you have a Small NAND SLIM or FAT console it would be a good idea to do one or both of the following:
In the XMB perform a system backup to save installed Homebrew you may have and gamesaves etc.. to an external device (i did this with my slim and it worked perfectly, all my installed signed homebrew from 3.55-jb works in retail 3.41 now)
make a COMPLETE backup of your HDD on your ps3 using ftp, although i dont think installed packages can be moved back over simply by ftp. i only tested the first method.
And now to downgrade:
3.55 Downgrade Files
Multiupload.com - upload your files to multiple file hosting sites!
you will need a downgrader dongle, search the forums for a DIY or buy one, or get an android/iphone, or an ipod nano, etc...
1) Unplug or switch off your console and then switch back on or plug back in.
2) While still OFF connect your Jailbreak/Downgrade device and press POWER then quickly Eject, you PS3 console should turn itself off automatically
3) OPTIONAL - Turn your PS3 on to verify you are in Service Mode (you will see a big red box, you can't miss it) then turn your PS3 back OFF
4) Place the lv2diag.self (FILE 1) from the archive and the PS3UPDAT.PUP (3.41 FW) from the archive on the root of a usb device and plug into the rightmost port on your console (dev_usb0)
5) Power on your PS3 with the usb device in and have a coffee, it can take a few moments for the PUP to install, your PS3 will turn off automatically
NOTE: if your system seems unresponsive and the light just stays green for ten minutes or more you need to use a different usb stick. i've had sporadic results with several different sticks.
6) Power your ps3 back on, you should still be in service mode, check your FW version now to verify you have downgraded successfully. Turn Off
7) Remove previous archive files from usb stick and now place lv2diag.self (FILE 2) on the root of your usb stick
8) Place usb stick in rightmost port of your PS3 (dev_usb0)
9) Turn PS3 back on with usb in place, it should turn itself off very shortly after.
10) Turn your PS3 back on and go through the configuration again.
Once you have completed the above process you will be on a modified 3.41 that has it's vsh changed to 3.56 (was needed in order to downgrade from 3.55). If you plan to stay on 3.41 you can stay on this firmware. If you ever plan on upgrading to a higher firmware you will need to go through the downgrade process again, but this time have a OFW on your thumbdrive that is less then 3.41 (Ex 3.40, 3.20, 3.15) but higher then the version that came on your console. You can use the same files from this post, but your PS3UPDAT.PUP must follow the rules above.
5C3B09C7FB0655D3F8852D3AAD778025 PS3UPDAT.PUP (3.41 FW)
099F33A7967F99E91C07E870FD78B3DB Lv2diag.self (FILE 1)
7A20BFDAE65EEFB47A4425DB1B52DCDE Lv2diag.self (FILE 2)
Thanks mathieulh, solidpsycho, and everyone else.