Broken Ribbon Repair

[Time2Retire]

I have a ExoPC tablet that I got cheap on fleabay. There were problems with the battery charging (which I fixed), but I had to open it up to fix it. I read through the ExoPC forums, and found warnings to be careful of the touchscreen ribbon when opening the tablet. I was VERY careful, but still managed to tear the ribbon off of where it was attached to. I did not realize just how fragile this connection was.

I found one How-To on repairing a ribbon on an Apple mouse, using conductive epoxy:

http://stcwk.blogspot.com/2010/03/ho...bon-cable.html

I thought that I could do the same procedure with this ribbon. I have bared both sides of the connection, but have yet to finish the job. The ribbon is very tiny, so the possibility of bridging the traces is very real, even with using conductive epoxy.

My plan was to do this:

1) Tape the connections in place using clear packing tape on the backside.
2) Use an X-acto knive to cut spaces between the traces, leaving gaps between traces.
3) Then apply the conductive epoxy to the traces, fixing the severed connections. The gaps I cut would prevent the epoxy from bridging the traces accidentally.
4) Use more packing tape, on both sides, to reinforced the fixed cable.

Anyone see any problems with this solution? I was wondering if the packing tape may be conductive, and not a good choice. Opinions would be greatly appreciated.

[sofTest]

Re: Broken Ribbon Repair

Might work. I would probably try soldering, and use liquid tape to insulate and strengthening the work.

[Time2Retire]

Re: Broken Ribbon Repair

Soldering plastic??

It would melt before the solder even got to a flowable state.

[sofTest]

Re: Broken Ribbon Repair

The traces is not plastic. It's delicate work, but like repairing traces on a circuit board.

[Time2Retire]

Re: Broken Ribbon Repair

You cannot heat up the traces without the heat transferring to the plastic. I don't want to make things worse, I want to fix it. Have you done similar repairs? Not on circuit board, as that is a different animal.

[Time2Retire]

Re: Broken Ribbon Repair

I see there is something called "kapton tape" that may work to hold the two pieces together. When I googled it, I see some is just film, with no adhesive. Anyone have any recommendations on a good kapton tape to use?

[larrymoencurly]

Re: Broken Ribbon Repair

I see there is something called "kapton tape" that may work to hold the two pieces together. When I googled it, I see some is just film, with no adhesive. Anyone have any recommendations on a good kapton tape to use?

I don't know if it's good, but DealExtreme.com sells kapton tape with adhesive on it:

http://dx.com/s/kapton+tape

If you don't need heat resistant tape but can apply it after doing any soldering, ordinary Scotch tape or plastic packaging tape ("poly" tape -- polypropylene) is just as good.

[Time2Retire]

Re: Broken Ribbon Repair

I don't know if it's good, but DealExtreme.com sells kapton tape with adhesive on it:

http://dx.com/s/kapton+tape

If you don't need heat resistant tape but can apply it after doing any soldering, ordinary Scotch tape or plastic packaging tape ("poly" tape -- polypropylene) is just as good.

Thanks for the info, and looks like good prices too. I just ordered some from DigiKey, but at three times the price! Is DealExtreme a good place to get stuff from? I have never heard of them before.

[larrymoencurly]

Re: Broken Ribbon Repair

Thanks for the info, and looks like good prices too. I just ordered some from DigiKey, but at three times the price! Is DealExtreme a good place to get stuff from? I have never heard of them before.

I wouldn't expect high quality for no-name stuff (circuit boards for products can be incredibly bad) or even branded stuff (counterfeit, as mentioned in some threads here about caps, like the Teapos disguised as Sanyos), but the service is really good, and they're the place to go if you want to buy a Rigol oscilloscope, underwear, violin rosin, fish food, and NSW products all from a single source.

[Time2Retire]

Re: Broken Ribbon Repair

What are NSW products?

[larrymoencurly]

Re: Broken Ribbon Repair

What are NSW products?

NSW = Not Safe for Work, or items of an adult nature. Deal Extreme really does sell everything.

[ratdude747]

Re: Broken Ribbon Repair

What are NSW products?

Blow up dolls, pron, dill rods, adult toys, etc. Anything you can find at the XXX store and half of what is found at Spencer Gifts.

[Time2Retire]

Re: Broken Ribbon Repair

NSW = Not Safe for Work, or items of an adult nature. Deal Extreme really does sell everything.

I always saw this as NWS, but same meaning.

[Duncanbest]

Re: Broken Ribbon Repair

FYR
http://www.youtube.com/watch?v=E49tv...eature=related

[Time2Retire]

Re: Broken Ribbon Repair

FYR
http://www.youtube.com/watch?v=E49tv...eature=related

Thanks, that looks interesting. I guess I could just bare both ends of the ribbom and just stick them on top of each other.

I found a USA seller, with the shortest/cheapest piece:

http://www.ebay.com/itm/3M-9703-Cond...item337a048045

[sofTest]

Re: Broken Ribbon Repair

You cannot heat up the traces without the heat transferring to the plastic. I don't want to make things worse, I want to fix it. Have you done similar repairs? Not on circuit board, as that is a different animal.

This is not my work, but you'll get the basic idea and technique.
http://www.youtube.com/watch?v=n1Lve6lHeOw

[soramarforever]

Re: Broken Ribbon Repair

Time2retire. How did you fix the problem with your battery not charging? can yiu share that information? thank you.

[Time2Retire]

Re: Broken Ribbon Repair

Time2retire. How did you fix the problem with your battery not charging? can yiu share that information? thank you.

I found the spec sheet for my battery, and it said that there was a low voltage threshold. If any of the cells dropped below this voltage, charging would be prevented on all the cells. One of my tablets cells had dropped below this voltage

I had a battery from netbook that had a bad charging board. I soldered leads onto these cells and piggybacked them onto a good netbook battery and charged them. I then took one of the charged cells and hooked it onto the low-voltage tablet cell. The effect was that they tried to equal each other in voltage. The low-voltage cell sucked the power from the charged cell. It increased the voltage enough that I could then charge it normally.

The two batteries were of different size. One was a flat Li-ion for the tablet, the other was a cylindrical Li-ion common in laptops and netbooks. But, they both were Li-ion rated at 3.7 volts. Still, I did it outside behind a sheet of plywood. I have heard of Li-ion batteries exploding!!

EDIT:

I found my posting of this on the ExoPC forums. In case I left anything out, here it is:

I purchased an ExoPC off of eBay for only $176 total. It has a bad battery, in fact it doesn't even recognise that it had a battery in it.

I opened the unit and removed the battery pack. I then peeled back the covering surrounding the battery pack. Inside is a circuit board and two Lithium-ion polymer batteries 3.7V (see the previous post for the attached pdf file for details). When I checked the cells, one was 3.12 volts, and one was 2.76 volts. According to the battery document, there is a circuit cut-off, if a cell goes below 3.0V, it will not charge it.

I looked all over on-line, and could not find a cell that would work for a replacement. So I decided to see if I could somehow charge the battery I have.

I have some standard Lithium-ion laptop cells (cylindrical), also 3.7V. I decided to try connecting one to the tabs of the low-voltage cell, and see if I could trick it to begin the charge cycle. I did this with alligator clips, and with the battery still disconnected from the tablet, I decided to check voltage once again. I found that the good/bad cell was now reading 3.25V. I disconnected the alligator clips, and found that the bad cell was now reading 3.12V!

I reconnected the battery, and was able to charge it!