[Upgrading, Modifying and Unlocking] twrock:
JIAYU G2S

The Jiayu G2S was released on January 1, 2013. It was a significant upgrade to the G2 with a lot of hardware changes. For the price, it had an impressive list of specifications:

MTK MT6577T ARMv7 Cortex-A9 Dual-core 1.2GHz processor

GPU: PowerVR SGX531

4 inch QHD IPS screen, 960x540 pixel display, OGS (One Glass Screen)

Dual SIM cards supporting GSM 850/900/1800/1900mhz & WCDMA 3G 2100mhz network (only one 3G slot)

1GB RAM / 4GB ROM

Supports up to 32gb class 12 microSD card (TF card)

8MP rear camera, 2MP front camera

Supports WiFi a/b/g & WiFi hotspot, Bluetooth with EDR & A2DP, GPS & AGPS

Android 4.1 OS (Jelly Bean), multi-language

FM Radio

Gravity Sensor, Proximity Sensor, Light Sensor, Magnetic Sensor, Gyroscopic Sensor

2200mah battery

Size: 125 x 61x 9.9mm

Weight: 145g with battery

Overall, I really like the look and feel of the phone. Except for the ear speaker hole, the front is one solid piece of glass, wrapped around with a very solid metal frame. The metal frame is not just a thin piece of sheet metal, but is cast metal, provides for complete rigidity for the whole phone, and should do a good job of protecting that large piece of screen glass. This also means that the phone has a bit of weight, but that feels good in my hand. Additionally, I like the more rectangular design of the phone and the more square edge down the sides that the flat metal frame provides. It is very easy to hold onto.

Call quality is very good for me. Reception seems on par with other phones I've used. The wifi might be a bit weaker than my Huawei G300, but it is fine. The screen is very nice to look at and very sensitive, but you should read below about the "jump screen" problem. You should also read below about potential problems with GPS connection issues. I've now owned two of these phones. The first had the jump screen problem, and was replaced under warranty. The replacement has terrible GPS pickup, but no jump screen problem.

The large battery means that I have no problem getting through a day of use, and I probably could use it for two days without a charge most of the time. (But I do not use the phone for gaming.) The phone runs most of the time at 1001mhz or 250mhz when on, and will only jump to 1200mhz in extreme conditions. "Deep sleep" mode is for when the screen is off, but the phone will run at 1001mhz when charging no matter if it is on and being used or not. That is an issue for phones based on this MTK chipset and not exclusive to the JY G2S.

Jiayu includes a few apps targeting the Chinese market for this phone, but other than that, the OS is mostly "vanilla" Android Jelly Bean (AOSP). The phone comes already rooted, so freezing or deleting unwanted apps is a simple solution for what you don't want. There are a number of modified roms available already, including the Lewa rom (http://www.needrom.com/phone-roms/jiayu/g2s/). But you should note that later hardware versions of this phone have different components. You should make a note of what the rom version is that came installed on your phone so that you know what hardware version you are using.

"Jump Screen" Problem Solved?:

Many of the first batch of phones were plagued with screen problems. Commonly referred to as the "jump screen" problem, the result is that when scrolling through screens of data, the screen just "jumps" to a different location without any apparent reason. The screen also "quivers" when touching it, even if you aren't moving your finger. Jiayu promptly acknowledged the problem and tried to correct it with a quick ROM update released on January 9, 2013. (The build number of the ROM is: G2S 20130108-104044.) This ROM update did seem to work for some, but for others the problem persisted.

At this point, I personally don't know if the problem has been completely solved in the manufacturing of subsequent batches of the phone. My phone had the problem, and flashing the new ROM did not solve it. I returned the phone for replacement under warranty and did receive a replacement phone that does not have the problem. So whether or not there still is a manufacturing problem, Jiayu can replace the phone with one that works. However, see below for the GPS connection problem that I now have. :mad:

GPS Connection Problems:

There are also a number of users here who are reporting difficulty with weak GPS fix. My GPS fix on my first phone was excellent, but my replacement phone is not good at all. It has been suggested to install "Faster GPS" from the Play Store, which will let you set your location. Also, you can look at this post from later in this thread for more information: http://xdaforums.com/showpost.php?p=39975417&postcount=209. (Please post any solutions you discover in this thread.)

ROM Flashing:

One of my initial struggles was getting the official rom flashing tool to work. I finally got things going, and I hope I can help others who "just don't get it". :) So if you want some detailed instructions in English for how to flashing a new official ROM onto the Jiayu G2S, have a look at the second post. (If you are flashing a third-party rom, follow the rom builder's instructions.)

ClockworkMod Recovery:

"Thingbreaker" has provided us with a working CWM Recovery. Here's his post link: http://xdaforums.com/showpost.php?p=37521066&postcount=28

There are two ways to flash the CWM Recovery image: using the ROM flashing tool (harder) or using Mobileuncle Tools (easier).

To use Mobileuncle Tools, install it from the Play Store (free). Copy the CWM Recovery image file to the root of your SD card, making sure there are no spaces in the filename. Run Mobileuncle Tools and choose Recovery Update. Choose the recovery image file that Thingbreaker provided.

To use the ROM flashing tool, you first you need to understand how to flash a complete rom as explained in the second post of this thread directly below. After you know how to do that, then look at this post to learn what is different about only flashing the recovery image: http://xdaforums.com/showpost.php?p=37499848&postcount=23

Conclusion:

I do not recommend purchasing this phone. Period. Until Jiayu can do a better job of quality control, I don't recommend their products. There are other companies out there who's phones are only slightly more expensive, but who have a much better reputation for quality control.

Jiayu, if you are reading this, you need to do better! And you really need to improve your repair department as well. Sending me a replacement phone with a GPS problem causes me to wonder if you are using the "shuffle" method of passing around bad phones instead of repairing them. I'm NOT a satisfied customer.