[General Topics] Danny_Dewet:
If like me you have installed JUI via Fastboot but you have realized that has several problems such as: CPU 1.6GHz, Infrared disabled, touch screen in some games laggy and Google Chrome crashes, today we're going to reinstall the EUI of GrossoShop with TWRP Recovery.

WARNING: I and the forum are not responsible for any damage that you will find in your device, as always i have tested this guide found on 4PDA (Russian forum similar to XDA) then translated into English. This guide has been tested on the 6GB RAM variant, I do not know if the 4GB version works perfectly.

NOTE: All files can be found at the bottom of the thread!

REQUIREMENTS:

Device with JUI ROM installed

PC

USB cable

Follow the guide carefully

STEP 1: TWRP 3.1.1.0 Installation

1) First of all we must install the Recovery TWRP then download the ZIP file containing the TWRP 3.1.1.0

2) Unpack the file where you want, and open the CMD in the folder

3) Check in the device if in the settings the OEM unlocking is activated, then go to Settings > device information and press 5 times on Number Build, now go in the Developer Options and check if the option is activated

4) Now turn off the device and restart it in Fastboot Mode, to start the device in Fastboot Mode press the power button + volume key down after connect the device to the PC

5) If you are on Windows 7 most likely the device will be recognized while if you are on Windows 10 the device will not be recognized so we have to install the drivers manually, so you have to hold down the power button until it shuts down and start the system normally. As you will see on the PC you will open a unit containing a setup to install, install the setup (the device must always be connected to the PC). Now restart the device in Fastboot Mode power button + volume key down and connect it to the PC. Now if you open the control panel and go to device management the device is not recognized, so we have to install manually the drivers, then right click on the unknown device - properties - driver - update driver - look for the driver software in the computer - browse ... now you have to go to C:\Program Files (x86) and choose the yulong folder. Well now the drivers are installed correctly.

6) Now we can install the TWRP Recovery, so let's go back to the previously opened CMD and type these commands in sequence

fastboot oem unlock-go

fastboot flash recovery recovery.img

fastboot boot recovery.img

Now the device will be restarted in Recovery Mode and you will see the TWRP 3.1.1.0 installed to change the language press the right button and make a swipe to confirm.

STEP 2: Revert to EUI (change Bootloader and EUI Installation)

7) At this point we have to do a conversion of the bootloader, but first we have to do a Factory Reset and then we will lose all the data like photos, music, etc., then save the important data in your PC and continue with the guide, now from Recovery go on Wipe, click on Format Data and type Yes to confirm, at the first attempt the recovery can give you some errors written in red, do not panic return to the home of the recovery go to Reboot and select Recovery. Once back in the Recovery we make Format Data again and this time it should work without problems. Once you've done this, let's go on Wipe again, go to Advanced Wipe and select: Dalvik / ART Cache, System, Data, Internal Storage, Cache and do a swipe to confirm.

8) Once the device is completely cleaned, download the conversion file (that you find at the bottom of the thread) and copy it to the device from recovery, after we go to Install, select the zip file and do a swipe to confirm, it will take a while of time do not worry. Once finished go on Reboot and select System, most likely the device will not start you will always see the Coolpad logo do not panic, force the shutdown by holding down the power button and restart it in recovery mode by holding down the power button + volume key up. Now we have to do an advanced cleaning so go to Wipe > Advanced Wipe, select Dalvik / ART Cache, System, Data, Cache and do a swipe to confirm. Now copy the GrossoShop ROM in your device, go to Install select the ZIP file and do a swipe to confirm, wait for the ROM to be installed, after go to Reboot and press on System.

Perfect! We brought our Cool Changer S1 back to original ROM!

DOWNLOAD SECTION:

Conversion Rom (bootloader): https://drive.google.com/file/d/1xqau8Rm-USvF33ioH2LKkWFf_D8m_faI/view

EUI GrossoShop ROM: https://mega.nz/#!YVdDHQTT!pCOA8P0eCoy9bPhiqrBdNF1Dg5tjL3CB_DV6ImlSBVI

TWRP 3.1.1.0: https://drive.google.com/file/d/1FgSIy2vpl9QkmndYCD9NMzLM5rHqLJkM/view

Original Thread (Russian): https://4pda.ru/forum/index.php?showtopic=822330&st=2920#entry70707812

Thanks To:

4PDA Forum

Androidiani Forum

GrossoShop Blog