Repairing equipment with horrid IDC ribbon cables. - Page 1
Forum section: electronics / repair

author: Simon Spiers
author_rank: Regular Contributor
timestamp: March 10, 2018, 02:57:13 pm
content: I have just finished repairing what should have been a fairly straight forward repair turned into one of those nightmare jobs you wished you'd never startedI bought some years ago a Pioneer A-757 Stereo amplifier from a local hifi collector. The amp was listed as intermittent on output so I assumed it was most likely in need of the switches and pots cleaning.After getting it home and plugging it in, I used it for a few days without an issue. That was 4 years ago! Last week I dug it out and tried it again instead of my usual amp. For a while it worked fine but them the left channel became distorted and faded in an out. I could tell this was a power supply fault as the drive was clipping at very low levels. I removed the base and soldered a dry TO3 regulator feeding the preamp section once I managed to get all the wires out of the way of the PSU board thats mounted under the main amp section.Happy with the repair I played the amp in the workshop for a while without an issue. I then tried the phono stage......Dead!Now a bit frustrated I pulled the bugger apart again only to find a short to one of the regulators on the phono preamp. As I had never used the phono stage before I could not remember if this section had ever worked anyway. To cut to the point after I had removed the PSU board to fix the regulator I had removed 3 IDC type ribbon cables that feed power to various sections of the amplifier. 3 hours of head scratching eventually found the problem. There ribbon cables have a stiff conductor that is inserted into the connector mounted on the board. If all the connectors are not perfectly straight they can miss the metal connection and jam behind the connectors plastic case out of sight or worse still two wires can short as the both go into one of the holes together.I have added a link so you can see the cable i am talking about. I think i'm not the first to be caught out by this hobable design, anyone else come across this?

author: tooki
author_rank: Super Contributor
timestamp: March 10, 2018, 03:35:13 pm
content: I think I found the 15 second spot (at 27:50, for those playing along at home) in that 35 minute video where you actually show the connector on the board. It looks like it’s really just a terminal strip made for solid-core ribbon cables, using a clamp mechanism similar to what’s used on flat-flex connectors. (You did press the clamp down, right? You didn’t show in the video.)FYI, that is by definitionnotan IDC cable, because IDC stands for “insulation displacement connector”, and that’s exactly not the case here, in that a) the insulation is stripped, not displaced, and b) there’s no connector attached to the ribbon at all. (Just because something is ribbon cable doesn’t make it IDC.)

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 10, 2018, 05:34:31 pm
content: Yeah, not IDC. Don't those connector housings pop open if you pull on them? That's how they work in my ancient Kenwood. They're zero insertion force. I haven't had any fail, but that's a sample size of one (1) 1990s Kenwood receiver kept in ideal conditions...

author: tooki
author_rank: Super Contributor
timestamp: March 10, 2018, 07:07:52 pm
content: Hahahaha yes, ZIF, that’s the correct term for what my brain plopped out a meandering description of! I couldn’t think of it at the time! Thank you, Alex!

author: Simon Spiers
author_rank: Regular Contributor
timestamp: March 12, 2018, 03:20:12 pm
content: . Yes of course not IDC at all! Bloody horrid thinks though. Yes there is a pull up clip that allows the conductor to mate (similar to the clamps used on flat flex cables). I assume they are reliable once mated though?