I suppose that your problem is that the 3.5 mm jacks (TRS) got damaged and you have connectivity problems (some speakers don't have sound, or there are interruptions while moving the jack/wire)
Most good audio systems are modular, in the way that the other end of the input audio cable is not hard-mounted in the speaker or amplifier enclosure, but have another TRS or RCA jack. If you're lucky to have this kind of system, the problem is easy to solve - just take a ride to the closest electronics / multimedia store (or even some PC equipment stores) and buy a replacement cable having the same connector types - ones having metal outer jack casing tend to be better - and appropriate length to the other cables.
If your audio system doesn't have such modularity in it's wiring, there are two ways to solve the issue, but require some electronics experience. If you don't have such experience, it's best not to try out yourself - either return it to warranty repair (if it's still in warranty), either call your technician friend to sort that out.
If you do have experience in electronics, the two ways to solve that (done that myself many times over) are:
- cut cable near the defunct jack and install a new one (requires soldering skills and some tools), using a new 3.5 mm TRS jack (can be found at most electronics stores) [Recommended]
- or, if the problem is in the wire, and replacing the jack doesn't solve the problem, dismantle the speaker or amplifier enclosure and find the corresponding PCB output point corresponding to the problematic audio channel; desolder the existing 3 wires (don't forget to use a soldering pump to extract the remaining alloy and be careful at heat-sensitive components) and replace the entire cable with a new one having a pre-installed jack at the other end. Don't forget to use a cable of the same length as the other audio input cables
Warning / disclaimer: tools used in this process can cause injuries and/or burns if not handled correctly. Do not attempt to do the operations previously described unless you're a qualified electrician / technician / engineer. Me or TH cannot be held responsible of any injuries / mishaps / malfunctions encountered in the described process.
Also, there are plenty of articles on the web detailing how to install jacks, Google it
Don't forget to test your new cables using an Ohm-meter so that there are no short-circuits or disconnections.
For aesthetic and impedance reasons, it may be nice to replace all the jacks or wires if you replace one. Not only that the cables may look different, but they may also have different impedance compared with the other jacks / wires. For most multimedia applications this is unnoticeable, but I prefer having the same type and impedance of cables from the mixer to the DAW / multi-track recorder / other equipment.