I just updated my solidoodle 3 printers firmware tonight. It has the Printboard Rev E, my operating system is Windows 7 64bit

These instructions I compiled after talking with Adrian, and reading the existing wiki (http://wiki.solidoodle.com/update-firmware)
A: Download the Arduino IDE (www.arduino.cc)
B: Download Teensyduino (http://pjrc.com/teensy/td_download.html)
C: Download the firmware  (https://github.com/ozadr1an/Solidoodle- … in_v1_beta)
D: Download the upload BootloaderHID (http://blog.lincomatic.com/wp-content/u … derHID.zip)

1.    Install Arduiono IDE
2.    By default it installed in C:/program files/Arduino (or program files C:/program files(x86)/Arduino)
3.    Install Teenyduino
4.    It will ask you where the arduino install is, point it to the above folder
5.    Unzip the firmware file to a folder you will remember
6.    Open the Arduino.exe (shortcut put on your desktop after the Arduino IDE installed
7.    Click Tools, Board (might say Board:Arduino Uno) and select the Teensy ++2.0
8.    Click Tools, Serial Port, and change it to the port of your printer
(If you are unsure, and using windows, click the start button, right click computer, click properties, click device manager, and click on ports. Your printer will be the one listed as “USB serial port (Com X) write down whatever the x is, and put it in step 8)
9.    Click File – Open
10.    Browse to the folder you extracted in step 5, select the file (in the marlin folder) named Configureation.H , double click it or select it and click open
11.    You will notice that there are several tabs across the top: Marlin, Configuration.H, ConfigurationStore.cpp etc, select the Configuration.H tab
12.    Scroll down until you see (in black as the grey is comments and effects nothing)
#define SOLIDOODLE_VERSION 2 (line 22 on mine) Change to #define SOLIDOODLE_VERSION 3                 
13.    #define MOTHERBOARD  62 (line #76 on mine…you can tell the line by clicking the code, and looking at the bottom left, a number will be there, this is the line of code)
Change it to read #define MOTHERBOARD 81
14.    find #define TEMP_SENSOR_0 1 (line 120 ) and change to #define TEMP_SENSOR_0 5
15.    find #define HEATER_0_MAXTEMP 225 (line145)  change to #define HEATER_0_MAXTEMP 290
16.    350C is the max the thermister can is good for, the hotend can go higher, but you’ll need a thermocouple instead of the thermister
17.    In the top arduino menu, click Sketch, then Verify/compile
18.    If you installed Teensyduino, it will pop up a window, just close it
19.    If your sketch does not report errors and simply gives you the Binary sketch size and memory use, it is safe to upload. If it reports errors, you have made a syntax error, and should recheck those lines you changed.
20.    Before doing the final compile, click file – save (if you do not, it will not upload the changes)
21.    Hold down SHIFT and click Compile
22.    There has been a .hex file created. Marlin.cpp.hex, in my case (windows 7) it is under C:/users/whateverYourProfileNameIs/AppData/Local/Temp….it will be in the folder
named build-xxxxxxxxx.tmp (the x’s are a string of numbers) created today. You must have view hidden or system files enabled in folder options (control panel. Have view folders by icon instead of category enabled, folder options,view, check Show hidden files and folders)
23.    Unzip the BootloaderHID.Zip (step D) to a folder
24.    Copy the Marlin.cpp.hex file, and past it in the folder above (the bootloaderHID folder
25.    Make sure your computer is connected to the printer via usb cable
26.    Add a jumper to the BOOT pins on the printboard (back of the printer) or bend the 2 pins so they are touching , then press the RESET button
27.    Open a new command window (click the windows start button, and in the search programs field (windows vista or newer) type CMD.
28.    Within the CMD window, navigate to the folder you unzipped the BootleaderHID to in step 23
29.     Type “hid_bootloader_cli -mmcu=at90usb1286 -w -v Marlin.cpp.hex” (no quotations)
30.    It should say something like “read Marlin.cpp.hex xx bytes, xx% usage, found halfkay bootloader, programming…………………..Booting
31.    Remove the jumper, or unbend the boot pins on the printboard (back of the printer)
32.    Press reset
33.    Verify that you have updated them, start up Repetier Host.
34.    Click Connect
35.    Look at the bottom of the screen, you will see a greeting msg when you connect it should now read
02:09:14.238 : echo:Unknown command: ""
02:09:14.405 : FIRMWARE_NAME:Marlin V1; Sprinter/grbl mashup for gen6 FIRMWARE_URL:http://github.com/mlaws/solidoodle2-marlin/ PROTOCOL_VERSION:1.0 MACHINE_TYPE:Solidoodle EXTRUDER_COUNT:1
02:09:14.405 : echo:Active Extruder: 0
If you see the address changed to github.com instead of solidoodle, you know you're golden