First, you need to know you have use a PC to update your PS3 JB King firmware. and this guide is for updating to V2.4, if new firmware releases in future, just use the latest firmware and same method to do the update, ok, let's get it started.
Step1, At first, you should download some files. Including: PS3 JB king firmware V2.4 PS3 JB King Update Tool and PS3 JB King Driver, you will get three Rar format files.Including "Driver.rar", "JBK Upgrade Tools.rar" and "jbking 2.4.rar"
Step2, Installing the PS3 JB King driver in your PC.
Step3. After you install the driver, press the button which attached in the back of the PS3 JB King, press it tight and then insert the PS3 JB King to one of your PC USB interfaces.Do not loose your hand until you see "STM Device in DFU Mode" in the bottom right corner of your PC screen. And you will see "STM Device in DFU Mode" in your PC Device Manager. Which means the PS3 JB King has been connected successfully with your PC.
Step4. Extract the "JBK Upgrade Tools.rar" and "jbking 2.4.rar" you will get fold named "JBK Upgrade Tools" and open the folder, you will see five files below.
Step5. Extract the "jbking 2.4.rar", you will get folder named "jbking 2.4", then you will see two files below
Step6. Start Updating the PS3 JB King
Step7. After step6, you have updated your PS3 JB King with "upgrade2.4.dfu", then unplug your PS3 JB King from the PC, Wait 8 seconds, notice, you should wait about 8 seconds, then insert the PS3 JB King to the PC USB interface again,
Step8. This time you will do the step6 again, but choose the other update file "spi 2.4_upgrade.dfu" and then click "Upgrade", it will start updating and wait until you see "Update successfully" This update will take a little longer, about 5 mins, please be patient. dont unplug your PS3 JB King until you see "Update successfully" .
Step9. Unplug your PS3 JB King, If your PS3 has installed the PS3 True Blue or PS3 JB King V3.55 CFW, power on, check the system info, if you see the pic below, congratulations, your PS3 JB King is in the latest firmware,