Problems with Samsung u700? Let’s fix its flex flat cable!

I own a Samsung U700. In my opinion, a part from some little problems (metallic silver edge painting flaking off and the touchscreen buttons sometimes irresponsible or too sensible), I never had something big to complain about in my 9 months with it.

The great stuff from this phone is definitely a great call quality, something which not all phones have. Also notably is its battery life which can last you 4 days of regular usage.

I also appreciate the good PC software which comes with the phone. It’s easy to use but full of features. I’m also happy that the phone also works pretty good under Linux with Kmobiletools, a must-have feature for a Linux only guy like me.

Recent issues

In the last month the phone started acting weird. The touchscreen buttons didn’t work anymore, it just seemed that the phone would hangs.

I started thinking of some software issues: I hard reseted the phone. Nothing changed. I reinstalled the firmware. Nothing changed. I upgraded the firmware. Nothing changed.

Guess what? It probably wasn’t an issue with the firmware. I started thinking that the problem could be hardware.

I started googleing around looking for people with similar issues and I finally understood that the problems could be very well related to some hardware issues.

The Flex Flat Cable

Some users on various forums suggested that my problems could have been related to a damaged Flex Flat Cable.

This is the cable which in the U700 connect the lower part of the phone to the sliding part (with the screen, speaker, camera and touchscreen buttons). All the data such as screen images, camera pictures, speaker sounds pass through this cable from the main board which is located in the lower part of the phone.

Unfortunately, each time one opens the phone, the cable slides between the two part of the phone. In the long term, as the cable is thin and soft and this movement causes frictions between the cable and the parts, the cable consumes itself. the damage of the cable could results in weird effects on the phone.

Some issues that could be related to a flex cable damaged:

  • screen: black or reverted image, disturbance
  • audio: non working speaker or ringtone
  • power button: unable to switch on the phone
  • camera: unusable or acting weird
  • touchscreen buttons: unusable or acting weird

The funny thing is that, depending on how fast you open the phone, problems can actually be hided as the cable does not break contact.

Another thing to note is that once damage starts it progressively get worst so that you’ll get more issue with time. Unfortunately the damage degenerates till a completely broken phone.

In the picture below you can see the detail of my broken flat cable. The silver colored area is where the damage occurred. You can understand how that could impact the data transmitted over the cable.

My Samsung U700 broken flex flat cable: Note the silver colored area. That’s the damage. The right connection have been accidentally cut out during the removing, that’s why it’s missing.

Fixing your Phone

Do you know the good news? Replacing the flex flat cable on your Samsung U700 is possible and actually pretty easy. I replaced the cable by myself and the phone is now working again without any problem at all!

I only tested the following procedure on my Samsung U700, but it will probably work as well on successors phones, such as the the U700 Evo. Please post a comment if you have been successful on other phones.

DISCLAIMER: The following procedure could cause damages to your phone. Opening your phone could break its warranty. Proceed only to your risk and knowing what you are doing.

Needed Tools and Replacing Parts

I suggest you to proceed only once you get all the following tools. They are pretty common tools, if you don’t have them you could ask to your friends or family. Ask to the geeky people.

You will need:

  • a precision soldering iron
  • a precision screwdriver set: you’ll mostly need a very thin crosshead screwdriver but I also advice you to have a thin flathead screwdriver. It’s pretty useful to separate composing parts joined like “puzzle pieces”.
  • two Safety pins: one little, the other normal sized. You’ll find them useful during the disassembling procedure.

Obviously you will also need a new Flexible flat cable for your Samsung U700. You shouldn’t have problems buying one on the internet. I bought mine from ebay, new and sealed, for 10 Euro including shipment. If you are going to buy on ebay just search for u700 flat cableu700 flex cable or similar.

Disassembling

The first thing you have to do is to disassemble the phone. I found a quite detailed video on youtube made by cr4ig.

You can see the video below:

I have a backup of the video so contact me if for any reason the above video disappears from Youtube.

So, just follow the video above. I haven’t got any problems just use the tools and follow the instructions. Remember to always be very gentle: it’s a sophisticated device, it can be damaged easily. Be careful in not loosing any screws, they are really little and loosing them is pretty easy.

There’s also a part 2 of the disassembling video. You won’t need that. It’s about disassembling the screen but it’s not useful for repairing the cable.

Remove the Damaged Flexible Flat Cable

Samsung U700 flex cable soldering

Once you have followed the video you’ll find yourself with the phone disassembled. The bottom part of the phone will no more be connected with the screen part.

The flat cable will be only connected to the screen part. The annoying thing is that it is not only plugged but also soldered to the chip board.

So, you will need to unsolder it out. I suggest you to put your flathead screwdriver below the connection and using the soldering iron melt the soldered zones, they are on the sides of the connection.

Then push the cable away of the connection using the flathead screwdriver while you are melting the soldering. I suggest doing one soldering, push away that side, then the other one.

Insert the new cable

Now you can insert your new cable into its connection to the board. For best results you should solder again the cable. Personally I didn’t do that because it looked just pretty stable even without soldering.

Just be sure to insert the cable with the same orientation as in the picture below.

Samsung U700 new flex flat cable: Pay attention to the orientation of the cable. The new cable just looks sexy to me.. seems that it’s saying I’ll work great! 🙂

Insert the bottom chassis

It’s now time to add the bottom chassis. The flat cable needs to pass through it. You can see how from the picture below.

Samsung U700 bottom chassis

Plug the CPU circuit board

Next you have to replug the CPU board with the cable. This has to be done with the board upside down. See picture below.

Samsung U700 plugging board

Once you did that flip the CPU board and reinsert it in the plastic chassis.

Samsung U700 flipped board

Final Reassembling

Once you get to this point you are ready to reassemble everything together. It’s mostly a matter of following the disassembling video at reverse. You shouldn’t have problems.

Screw back the screws into their places, insert the battery, cross your fingers then start the phone.

Conclusions

With this quite simple procedure I’ve been able to repair a strongly broken and unusable phone. Now it’s perfectly working and I’m pretty proud of have it fixed all by myself.

Moreover doing this by myself saved probably quite a good amount of money and saved days (months ?) of service time.

Did it worked? Problems? Let me know!

Then please post a comment below. I’m always glad when people find my posts useful.

If you find any problem following the procedure or you have suggestions to improve it I also suggest you to post a comment below and I’ll try to help you.

Scroll to Top