Opening Ribbon Cable Connectors

[obiwanjacobi]

I have a Behringer mixer where the input jack board is connected with two 8 channel strip boards via 2x2 40-pin flat cable connections. The problem is that the contact for some channel's inputs has gone bad. Signal is weak and when moving (exiting) the flat cable the signal fluctuates. On the channel-strip board the flat cables are soldered on the PCB and terminate in a normal connector.

Something like:


You can just make out those connectors at the top (left on the photo):


Question is:
Is there a trick to fixing these connection problems?

If I do have to replace the cables, is there a trick to open the PCB (through-hole) connectors so I don't have to resolder 4x40 pin connectors?

Thanx, Marc

[mikeselectricstuff]

If it's intermittent at the connector then you really need to replace the connector - reterminating us unlikely to be reliable.

[Shock]

You can redo them, but if it's corrosion that won't help. You should make sure it's not bad joints on the PCB.

If there is slack in the cable you might find the breaks are close enough to reuse the old one, desolder it first from the PCB.

You can use a female socket (old PC IDE cable?) if it fits to to make it easier to recrimp. I push the cable on till it starts to bite then use a vice carefully to apply a slow even pressure.

I have soldered a few directly into the PCB before as well but this is painful, more so than re-crimping it and then has it's own issues.

[SeanB]

You can release them by popping the clips on the ends, but from experience you will be better off just buying new ones. If yours are soldered into the board then buy a female connector and a 40 pin solder pin post section if height allows, or put the pins on the rear of the board and terminate the cable to it there. Most common cause of intermittent joints is the IDC section on top of the unit losing tension, so you will be needing to replace it in any case.

[obiwanjacobi]

Bah, i dread desoldering 4x 40 pins 

Yeah, I figured replacing the soldered connectors with headers because my supplier (farnel) does not carry them anymore. This will make swapping out the cables in the future a lot easier.

I did check the solder connections of the headers on the input board and they look okay (loosening a gazillion 1/4 inch jack screws and then putting them back!  ).

Any tips on the desoldering job are welcome (I only have a tin sucker and wick)...

[SeanB]

Chipquick will work here, as it will allow you to flood the whole connector at a single unit then simply pull it out in a single pass.  A hot air unit also works well, just get some sacrificial aluminium foil shields held down with Kapton tape to protect the rest of the board. A broad chisel tip on the iron as well helps, then after the connector is out clean the pads with braid then you can put the new pin header in the holes and solder it down. for those I have a soldering handle for my unit that has a flatpack tip on it, a broad Weller tip that does a good job of melting around 15mm of solder at once.

[mikeselectricstuff]

Bah, i dread desoldering 4x 40 pins 

Yeah, I figured replacing the soldered connectors with headers because my supplier (farnel) does not carry them anymore. This will make swapping out the cables in the future a lot easier.

I did check the solder connections of the headers on the input board and they look okay (loosening a gazillion 1/4 inch jack screws and then putting them back!  ).

Any tips on the desoldering job are welcome (I only have a tin sucker and wick)...

For through-plated PCBs, a good sucker is usually better than wick.
For something like this, where you only care about minimising PCB damage, I'd suggest cracking off the top of the connector and pulling the cable off. You can then unsolder each pin individually by pulling it out with needle-nose pliers while melting the solder.
Once you have the connector off,  fill the holes with fresh solder ( leaded of course) , then clear using  iron on one side and sucker on the other.

[obiwanjacobi]

For something like this, where you only care about minimising PCB damage, I'd suggest cracking off the top of the connector and pulling the cable off. You can then unsolder each pin individually by pulling it out with needle-nose pliers while melting the solder.
Once you have the connector off,  fill the holes with fresh solder ( leaded of course) , then clear using  iron on one side and sucker on the other.

That is an excellent suggestion, thanx Mike!

I was thinking of getting out the hot air gun but that thing is far from subtle...

[ciccio]

From my (little) experience with maintenance of Behringer mixers, I suggest you to be extremely careful with the PCB: board quality is average, and it is very easy to damage pads and tracks.
If you want to replace the soldered connectors I suggest to carefully break the plastic, remove the cable and then remove the connector's pins one at a time.
Then it will be very easy to clear the holes and pads from solder with a good sucker pump  or a desoldering tool.

Best regards

[obiwanjacobi]

Yeah, that board needs some care - those pads are tiny too. I did what you said and removed the top cover of the connector and could then desolder and pull out each pin individually. Clearing out the holes took the most time and some holes (with more thermal mass) were very stubborn.

I have one board done (2 connectors) and will wait for my parts to arrive first before taking on the other board. That way I have an original to check pin orientation against.

Thanx all.
Marc

[David_AVD]

You really don't want to reuse any kind of crimp connector like that.  It will never be reliable.

Also never crimp a new one on the same spot on the cable.  Cut the cable and use a new connector.

If the cable is going to be too short, you'll just have to suck it up and replace it entirely.

[SeanB]

If the cable is too short, and you do not want to unsolder the other end simply get a cable mounting socket and a cable mounting plug, or just use a PCB pin section and remove the plastic holder then insert the pins in the one socket, so you can make an extension cable.

If it is a 40 pin cable just get cheap PC ATA cables, they are cheaper than the connectors and if the cable length is right they are a quick fix.

[flynwill]

Bah, i dread desoldering 4x 40 pins 
Any tips on the desoldering job are welcome (I only have a tin sucker and wick)...

Once you have the top off of the connector and the ribbon cable removed you should be able to grab the pins from the top side with your needle nose pliers.  Setup the board on edge somehow (panavise?) and then heat the connections one at a time with your iron while pulling on the pin, and they will slide out.  (The soldering heat is enough to soften the plastic).  Once they are all out use your solder wick to clear the holes.

[obiwanjacobi]

Once you have the top off of the connector and the ribbon cable removed you should be able to grab the pins from the top side with your needle nose pliers.  Setup the board on edge somehow (panavise?) and then heat the connections one at a time with your iron while pulling on the pin, and they will slide out.  (The soldering heat is enough to soften the plastic).  Once they are all out use your solder wick to clear the holes.

This is exactly how I ended up doing it. 

[obiwanjacobi]

One little tip: make sure the holes are properly desoldered. Especially when the hole is just big enough to receive the connector pins and extra solder still left in the hole will push pins upward if forced. So keep at it until the connector goes in without any force.

[obiwanjacobi]

Everything worked out great. I got a working mixer again without any glitches.

Thanx everybody for their input.
Marc