The Dev-Team has updated RedSn0w 0.9.14b2 to solve and improve the downgrade baseband 06.15 iPad iPhone 3G and iPhone 3G. MuscleNerd took the opportunity to add an option to create a custom firmware DFU Mode for those who a Home button or power off on their iPhone.
This version covers three types of iPhone: iPhone 3G, iPhone 3G and iPhone 3G Old Boot New Boot. Here's the changelogs:
Connect your iPhone in normal mode, then click "Jailbreak" redsn0w then identifies the model and the version of Baseband (you no longer need to pre-select the IPSW).
Choose the "downgrade baseband iPad".
Turn off your iPhone and follow the instructions to enter DFU mode.
If the downgrade fails, the Dev-Team application logs Redsn0w post on their blog:
Use the "Extras-> Even More-> Backup" to retrieve a copy of / var/mobile/Media/redsn0w_logs, then extract the zip files of newspaper and paste in comments on the blog of the Dev-Team.
Caution: The iPhone 3G manufactured after week 34 of 2011 or later have a NOR chip is incompatible with the baseband 06.15.00, so do try to install it if it is assured of the brig your iDevice!
NEW FEATURE WITH IPSW DFU MODE:
This feature is intended for users with a Home button or Power broken or defective. It allows you to enter DFU mode to restore it.
In redsn0w, go to "Extras-> Even More> DFU IPSW" and select an IPSW is currently signed for your iDevice. Redsn0w will create a version of "ENTER_DFU_" in the IPSW and you can restore it with custom firmware (beware, your screen will remain completely black).
0.9.14b2 redsn0w is available for Mac and Windows.