Flat ribbon 'cable' - Page 1
Forum section: electronics / repair

author: najrao
author_rank: Regular Contributor
timestamp: September 03, 2022, 08:04:26 am
content: I need to replace one in a V7 Dyson, (and hope the problem ends there). This is some 200mm in length, and just 5mm wide. It has a conductor pitch of 0.5mm, so 9 'pin' connector at each end. (Only 6 conductors are present, three are replaced by spaces, but a fully loaded cable can be used.).I can access only wider, i.e., with larger number of conductors, and propose to slit this to gain a 5mm/9 way cable. At least one end will need to be stripped and prepared to mate with the connector. Scraping off the plastic on one side without scoring the copper seems to be near impossible. And I can at best tin the exposed copper when I get that far.I need advice from anybody who has done this. Thanks in advance.

author: jpanhalt
author_rank: Super Contributor
timestamp: September 03, 2022, 08:55:51 am
content: I use heat and a spring clip to strip PVC from multiconductor wire (picture attached). I clamp the cable in the clip, blow hot air into it until I just sense the characteristic odor and pull.One could adapt that to just one side, e.g., lay cable flat, blow hot air from one side, and use a putty knife. Others have suggested just using a soldering iron from one side.Heat is probably the easiest. However, one might consider adapting a bladeless automatic stripper to srtip only one side by supporting the back/bottom side with something like double sticky tape and a thin metal sheet. A little heat would probably help there too.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: September 03, 2022, 12:17:58 pm
content: I have used a metal ruler across the ribbon wire and then use the ruler as a straight edge to guide a soldering iron to make a nice straight line across the ribbon.The insulation usually comes off cleanly after that.

author: pcprogrammer
author_rank: Super Contributor
timestamp: September 03, 2022, 12:38:40 pm
content: Is it not a cable like these on Aliexpress?https://nl.aliexpress.com/item/1005002468369055.html?Only there is no 9 pin version.A picture of the connector it connects to could help.

author: najrao
author_rank: Regular Contributor
timestamp: September 03, 2022, 01:35:52 pm
content: It takes a lot of dismantling again to take a picture. I did attach a picture,, of a comparable.

author: tooki
author_rank: Super Contributor
timestamp: September 03, 2022, 06:02:35 pm
content: Just buy one:https://www.aliexpress.com/item/1005001754581323.html(Literally the first Google hit for “0.5mm 9p ffc”.)The key is that this stuff isn’t called ribbon cable, but flat-flex cable (FFC). “Ribbon cable” refers to the stuff jpanhalt pictured, which is multiple stranded wires stuck together. (Even though FFCs are decidedly more ribbon-like than ribbon cable, ribbon cable has existed for much longer and already had that name.)You don’t normally strip FFC yourself, but buy it already finished with the stiffener attached to each end. Note that versions exist with the exposed copper on each end both facing the same side, or on opposite sides.

author: inse
author_rank: Super Contributor
timestamp: September 04, 2022, 06:23:42 am
content: I agree to tooki, you can cut those cables in width, but never in length.Distributors like Farnell sell them in all variants.

author: Ian.M
author_rank: Super Contributor
timestamp: September 04, 2022, 07:21:58 am
content: Its a royal PITA manually terminating a laminated flat-flex cable, but it can be done by extremely careful application of heat (as described by Jpanhalt and Wallace Gasiewicz) + scraping towards the end with a curved blade scalpel to peel off the insulation layer. The problem is: you need to weaken the bond of the top insulation layer to the foil conductors enough to peel it without weakening the bond of the foil to the bottom insulation layer so much that the conductors peel off as well. Practice on a scrap FFC before trying it on the one you need to get right.I reckon I've done dozens during my time in the service trade. This was before easy ordering of parts on the internet, so taking half an hour or more to reterminate the existing cable made sense vs the hassles of closing up the job, ordering a replacement, and then having to put it back on the bench when the part came in, with the risk that one would find there was sill another fault.OTOH nowadays its not worth even attempting the above if you can buy a FFC to fit, preterminated, unless you need it yesterday and your supplier only ships on the slow boat from China!

author: wasedadoc
author_rank: Super Contributor
timestamp: September 04, 2022, 12:23:32 pm
content: If you cannot or will not waitwouldfor a replacement FFC I would investigate the possibilityorof soldering 6 wires between the relevant points.

author: Rasz
author_rank: Super Contributor
timestamp: September 04, 2022, 05:42:02 pm
content: Quote from: wasedadoc on September 04, 2022, 12:23:32 pmthis, its a one off, its not likely you will ever pull it apart again, and its only 6 cables

author: Ian.M
author_rank: Super Contributor
timestamp: September 04, 2022, 07:49:52 pm
content: Quote from: Rasz on September 04, 2022, 05:42:02 pmThat's a reasonable fallback if the remaining good part of the cable is too short or if you can't strip the end successfully.

author: najrao
author_rank: Regular Contributor
timestamp: September 05, 2022, 06:22:43 am
content: This FFC is the one connecting the motor pcb to the display at the far end. It is critically routed with rubber seals at both ends to exclude dust. It is not wise to attempt replacing it by soldered wires, however thin. Any future disassembly (inevitable!) will become void. Soldering wires to tiny pads at 0.5mm pitch is not something I fancy.Aliexpress does not post to my country.In the event, I repaired the break in the existing cable by soldering a 0.15mm wire across, and mummified the wound with Kapton tape. I have continuity between both ends on all the six tracks (and no shorts). That the display is still faulty, nor does the motor show any sign of life, is another issue. Needs atinfeverto diagnose. I may get back for more help (new thread).I thank all of you who offered help.