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Help repairing a ribbon cable

sacentre

Sep 27, 2014
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Can anyone suggest what solvent I might use to remove the shellac or varnish or whatever the coating is, from this busted ribbon cable? It's out of an HP Elite x2 1012 G2 tablet and is the "touch cable" which enables the touch screen. The main display cable is fine and I can continue to use the tablet with a mouse and keyboard.

But I'd like to try to repair it if I can. As can be seen from the photo, I managed to bridge the first two tracks but had little success with the 4 thinner ones. The soldering iron kept melting the coating which contaminated the joint. I figured I'd have better luck if I could clean the coating off more effectively with a solvent (rather than trying to scrape it off with a blade). I might need to cut the broken ends back a bit and try to bridge the gap with bits of fine insulated copper wire. I have a good bench microscope for SMT work so it shouldn't be impossible as long as I can get a few mm or so of clean copper on each track.

Needless to say, if anyone can suggest a better alternative method for a repair like this, I'm all ears.

In case anyone is wondering, my first thought was to try to buy a replacement cable which is listed as p/n 924453-001, Cable Kit in the Maintenance and Service manual which I assume means both cables. My local HP can't or won't sell me the cable(s) saying I have to pay them to replace the entire LCD display screen with the cables. This would cost the best part of a $1000/-. I've searched all over for a supplier and can see the Cable Kit listed on many web sites with the price but so far haven't found one either with the part in stock or who can ship to Singapore.
Thanks for reading
Trevor
 

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Martaine2005

May 12, 2015
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Hi Trevor, I would patiently keep scraping.
Have you tried a flame quickly over the area?
Once you do it, don't forget some solder mask or varnish over the area.

Martin
 

sacentre

Sep 27, 2014
29
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Hi Trevor, I would patiently keep scraping.
Have you tried a flame quickly over the area?
Once you do it, don't forget some solder mask or varnish over the area.

Martin

Thanks, Martin. You're probably right: gentle scraping is the way to go. The problem isn't so much cleaning the top surface of the copper tracks. It's preventing the varnish between them from melting and contaminating the soldering. If I could find a suitable solvent that would cleans the stuff off, that would be ideal. I wonder if regular paint stripper or nail varnish remover (acetone?) would work.
 

sacentre

Sep 27, 2014
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And I would order it in a heartbeat but despite quoting the HP p/n it looks absolutely nothing like the original. It could be an electrical equivalent but there's no way to be sure.

HP Partsurfer has the original and quoted me SGD98/- but has no stock right now. I've emailed to ask when they expect stock to come in and confirm they will ship to me.

Incidentally, I had another call from my local HP trying to persuade me that this item IS NOT a separate part and must be ordered with the complete LCD assy!
 
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Harald Kapp

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I see. You sure have the right part number?
 

sacentre

Sep 27, 2014
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I see. You sure have the right part number?

Pretty sure. Page 31 of the Maintenance and Service Guide show the cables as "2 display cable" and "3 touch cable" and above on page 30 they are listed as "Cable Kit, p/n 924453-001"

It was my local HP that sent me a copy of this manual in the first place and even when I'd referred them to the same pages, they still wanted me to buy the entire LCD panel!
 

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73's de Edd

Aug 21, 2015
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Sir sacentre . . . . .

HERESHOWYOUCANDOITTOITANDREPAIRTHATBROKENRIBBONCABLETOTALLYSUCCESSFULLY . . .!

First, in the supplied illustration, seems that you have the LARGER 1 and 2 . . .Brown and Red foils already repaired.
Then we use the annotated 3rd . . .Orange . . . . mark-up to see that you distance down from the damaged foil break, far enough to have ample working room.
You use a SHARP rounded surgical scalpel or like X-acto knife blade to side scrape / clean the ORANGE slash area down to bare copper foil.
Same way with the other side, at the other ORANGE slash..

Scrape off its insulation coating and prep up an end of a piece of enamel / Formvar insulated copper magnet wire at one end to mate up with the length of the ORANGE slash. Rosin flux and tin both and then . . . ever so efffortlessly . . .solder tack an overlapping splice in place with the two PRE tinned surfaces.
Measure the length of magnet wire needed to make that curved path and cut the magnet wire for the end length of that splice to the end of that other ORANGE slash. Again, rosin flux and tin both and solder tack a splice in place.

Move down to the distance of the YELLOW dot area and repicate the two splices for that foil run.

The same then goes for the GREEN, BLUE and VIOLET traces.
Add a conformal coating or use spaced out micro-dots of adhesive to hold down your free space magnet wires between their solder splice terminations.

Considering that being the very worst case . . . . you might also be able to make the VIOLET trace jumper in place such as you have already done with the Brown and Red wire jumpers .
Then use the magnet wire procedure for the BLUE run and that resultant acquired distancing, THEN, might let you do another direct splice across the GREEN foil . . . you get the idea . . .

Thaaaaaaaaaaaaaassit . . .

PHOTO REFERENCING . . . . . . .
upload_2021-5-21_6-6-14.png

73's de Edd . . . . .

upload_2021-5-21_6-2-51.png

 
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sacentre

Sep 27, 2014
29
Joined
Sep 27, 2014
Messages
29
Sir sacentre . . . . .

HERESHOWYOUCANDOITTOITANDREPAIRTHATBROKENRIBBONCABLETOTALLYSUCCESSFULLY . . .!

First, in the supplied illustration, seems that you have the LARGER 1 and 2 . . .Brown and Red foils already repaired.
Then we use the annotated 3rd . . .Orange . . . . mark-up to see that you distance down from the damaged foil break, far enough to have ample working room.
You use a SHARP rounded surgical scalpel or like X-acto knife blade to side scrape / clean the ORANGE slash area down to bare copper foil.
Same way with the other side, at the other ORANGE slash..

Scrape off its insulation coating and prep up an end of a piece of enamel / Formvar insulated copper magnet wire at one end to mate up with the length of the ORANGE slash. Rosin flux and tin both and then . . . ever so efffortlessly . . .solder tack an overlapping splice in place with the two PRE tinned surfaces.
Measure the length of magnet wire needed to make that curved path and cut the magnet wire for the end length of that splice to the end of that other ORANGE slash. Again, rosin flux and tin both and solder tack a splice in place.

Move down to the distance of the YELLOW dot area and repicate the two splices for that foil run.

The same then goes for the GREEN, BLUE and VIOLET traces.
Add a conformal coating or use spaced out micro-dots of adhesive to hold down your free space magnet wires between their solder splice terminations.

Considering that being the very worst case . . . . you might also be able to make the VIOLET trace jumper in place such as you have already done with the Brown and Red wire jumpers .
Then use the magnet wire procedure for the BLUE run and that resultant acquired distancing, THEN, might let you do another direct splice across the GREEN foil . . . you get the idea . . .

Thaaaaaaaaaaaaaassit . . .

PHOTO REFERENCING . . . . . . .
View attachment 51841

73's de Edd . . . . .

View attachment 51839
Thanks Edd
You went to a lot of trouble creating those instructions. Thank you. They are pretty much the method I would follow but my first concern is to get as much of the lacquer off to prevent it constantly melting and flooding over the soldered joint. I keep having to clean it off again and again and this is just causing more damage to those thin tracks. I need to find a solvent that can thoroughly remove the coating from at least an 1" either side of the break. Only then can I concentrate on soldering. I got lucky with the two large tracks probably just because of the size. I'm going to try acetone nail varnish remover if I can find some.

I'm still hoping to find an HP parts supplier to buy the cable from but will most likely have to have it sent to a US address.
Trevor
 
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