[myTouch 3G, Magic General] Amon_RA:
After a lot of trial and error we finally did it! Many thanks to Jrbourque for being a tester with balls (he could have bricked his phone) :) and Haykuro for all the tips and tricks :p. Please give them credit where credit is due ;)

Proceed on your own risk, you might brick your phone!!!

This method is written for the original MT3G back in 2009, DONT USE IT on the Fender/MT3G 1.2!!!

CREATE and PREPARE your GOLDCARD

Please start a new thread in the general section if you have issues creating a goldcard, this how-to assumes that you have a working Goldcard.

- Create a Goldcard according to this tutorial (Sandisk SD-cards might not work, I used a Kingston 2GB SD and it worked fine).

- Copy sappimg.zip to your goldcard.

PREPARE your spare SD

- Format a spare SD FAT32 (not your Goldcard! :D)

- Download the 1.33.2005 hboot, rename it to update.zip and copy it to the root of your spare SD.

FLASH your T-Mobile myTouch 3G

Make sure are using fastboot from the latest SDK (release 3) !

- Power-off your device

- Insert the goldcard

- Power on while holding volume down (of fastboot your device and then press volume down)

- It should pick up the sappimg.zip and you should be able to flash it.

- Once the flashing is FULLY finished power off your device.

- Remove the goldcard and insert the SD (with update.zip)

- Power on while holding back (=fastboot) and connect the USB cable

- Download my RAv1.2.0H recovery and fastboot it :

fastboot boot recovery-RAv1.2.0H.img

- Once the recovery is booted wait a while

- Apply the update.zip (you are now flashing the 1.33.2005 SPL)

- Once the SPL is flashed you have to power off your device and boot it again in fastboot mode.

- The SPL should now read 1.33.2005.

- Power off your device and pull out the SD-card

- erase the update.zip on your SD-card (via cardreader)

- Download my RAv1.1.0H 32A based ROM and rename it to update.zip and copy it to the root of your SD-card (via cardreader)

- Insert the SD into your device.

- Power on while holding back (=fastboot) and connect the USB cable

fastboot boot recovery-RAv1.2.0H.img

- Apply the update.zip located on your SD-card

Revert to 32B Radio and ROM :

- Download your favorite 32B ROM and copy it to your sdcard

- Download the Ion radio image from the HTC site.

- Extract radio.img from ota-radio-2_22_19_26I.zip using your favorite rar/zip program.

- Download my 32B RAv1.2.0G recovery.

- Fastboot your mobile and connect it via USB :

fastboot flash radio radio.img
fastboot erase system -w
fastboot erase boot
fastboot erase recovery
fastboot flash recovery recovery-RAv1.2.0G.img

- press MENU to power off! (do not reboot)

- hold HOME and POWER to boot into recovery mode

- apply update

Original T-Mobile MyTouch 3G Splash Image (Thanks Haykuro)

Download it here

fastboot flash splash1 splash.nb

Un-Root your T-mobile MyTouch 3G

(and receive back those OTA updates)

- Download this nbh and rename it to sappimg.nbh (MD5 33D958062CC02BB2CEC157F68621D2FF)

- Copy sappimg.nbh to your goldcard (a normal SD might also work if you are using an engineerings SPL, give it a try and let us know :D ).

- Power-off your device

- Insert the goldcard (or SD)

- Power on while holding volume down (of fastboot your device and then press volume down)

- It should pick up the sappimg.zip and you should be able to flash it.

- Once the flashing is FULLY finished reboot your phone.