2025-03-31 - More Loudspeaker Repairs ------------------------------------- One of the first repair articles in my phlog[0] dealt with old loudspeakers that I had gotten for free when they were thrown away (some of them due to broken cables or other problems). I still had some more speakers that I never got around to, so I thought I'd write a short article on my adventures with those. Some speakers only had basic problems like broken cables, but I singled out two repairs that were at least slightly more interesting. First Set of Speakers --------------------- The first set of speakers[1] (Philips SPA 1312/10) started out as a simple cable repair. The cables connecting the two speakers to the base/subwoofer were broken around the plug, so I replaced those[2]. In this case, I used a 3.5mm plug made for soldering since I bought a few of those a while ago. The cable for connecting to a playback device also was broken around the plug, so I had to replace that as well[3]. This time, I used the end of a cable I had cut off from something else (I collect all audio cables from broken equipment in case I ever need them). As you can see in the picture, the heat-shrink tubing over the connection between the cables is a bit short. That's because I only had very short pre-cut pieces of tubing at the time, but I re-did that connection later when I had longer pieces of tubing. Even though I called broken cables a "basic problem" at the beginning of the article, I still want to add a few notes on how to fix them properly. There are probably better methods, but this way works for me. First off, it's always good to have extra flux on hand. Although this isn't really necessary for basic soldering tasks like soldering wires together, I find it still is very helpful to add a bit of flux on the end of the wire before soldering it. One convenient aspect is that it allows you to add solder to the tip of the soldering iron first, then touch the wire with that instead of having to hold both the wire and the solder at the same time so the flux inside the solder doesn't burn away before it ever reaches the wire. I usually just tin both wires this way, then hold them together and briefly touch them with the soldering iron to connect them. The second part does require some sort of "third hand" to hold one wire while holding the other wire and the soldering iron in your hands. If everything goes well, the wires should have enough solder on them after tinning that they'll be firmly connected after this. One annoyance with audio cables is that they often contain enameled wire, so the insulation has to be burned off first. I find that the best way to do this is to add a big blob of solder onto the tip of the soldering iron, then move that over the wire a few times so the enamel is burned off by the hot solder. Another annoyance with audio cables is that they contain multiple wires that all need to be connected, but once one of them has been soldered, you can't move the whole cable around as easily anymore. I usually solder one wire first so the cables are connected, then use tweezers to bend the remaining wires into shape while soldering them. Afterwards, I add some tape around each connection to isolate it from the others[4] (it's probably a good idea to clean the wires with isopropyl alcohol beforehand so the flux doesn't prevent it from sticking). I use heat resistant tape, although that probably doesn't matter too much (but if you use very high heat for shrinking the heat-shrink tubing, it might be relevant). Finally, some heat-shrink tubing can be added over the connection[5][6]. Of course, the tubing needs to be slid onto the cables before soldering them together, otherwise you can't get it on anymore because the plug is in the way (I *definitely* have never had to redo connections because I forgot to add the tubing beforehand). I happen to have a hot air station, so I use that to shrink the tubing, but you can just use a match or lighter if that's all you have (just make sure not to hold the flame too close to the cable/tubing so it doesn't burn or melt). When I started these repairs, I only had standard heat-shrink tubing with a 2:1 shrink factor and without added glue. That works, but it isn't really ideal because it doesn't give a lot of strength to the connection, and it doesn't work when the two cables being connected have very different thicknesses. To solve these problems, I recently got some 3:1 and 4:1 tubing with glue on the inside that melts when the tubing is shrunk. [7] shows a piece of tubing that I cut open after it was shrunk so you can see the glue inside. When I was repairing the speakers mentioned in this article, I didn't have that fancy heat-shrink tubing yet, so these pictures (4-7) were taken later when repairing another set of speakers. Those only had cable issues, though, so I didn't want to write much about them. One final note is that this method of connecting the cables relies entirely on the strength of the solder and the heat-shrink tubing. There are methods of splicing wires that add more mechanical strength, but I never really managed to perform any of those properly because the wires in audio cables are so small and I was only working with very short lengths of exposed wire. Considering how thin most of the wires are, the solder joint is probably stronger than the wire anyways, so it makes more sense to use good heat-shrink tubing with glue that holds the cables together and prevents stress on the actual wire connections. After this slightly longer than expected side note, let's continue the actual repair. Another problem with these speakers was the scratchy volume control. I already mentioned how to fix this in my previous article[0], so I don't want to repeat myself here. The only potentially useful piece of information I could mention is that the screws that need to be unscrewed to access the potentiometer are hidden underneath small foam pieces[8], so don't try to pry that bottom cover open without first removing the hidden screws. Once I fixed all of these problems, the speakers sort of worked, but one side somehow still wasn't working properly, so I decided to look inside the base/subwoofer. WARNING: This is a device that is connected directly to mains electricity. Do not open such a device if you do not know what you are doing as it can potentially kill you. The subwoofer is held on by four screws[9]. Once those have been removed, the circuit board can be accessed underneath[10]. The circuit board was also screwed in somehow, but unfortunately I don't have any more pictures, and I don't remember anymore because this was several months ago already. Luckily, I didn't even need to measure anything on the board because I quickly discovered a capacitor that was in very bad shape[11], which I could easily replace with a new one[12] (I'm guessing it was C35 since that one looks different than the other ones, but I didn't take proper notes when I performed this repair, so these pictures are all I have). Once that was done, the speakers worked without any problems. Disclaimer: I honestly can't say for sure that the capacitor was what caused the issue because I seem to remember that there may still have been something wrong with one of the cables when I replaced it (but my memory may not be entirely accurate). However, it definitely was in very bad shape, so I'm sure it was causing *some* problem. Second Set of Speakers ---------------------- The second set of speakers[13] (Philips SPA 2200/00) didn't have any broken cables, but the volume control was a bit scratchy, so I decided to try to fix that. WARNING: The warning given earlier in this article applies here as well. There are two screws on the bottom[14] that have to be removed in order to access the circuit board. In order to slide the board out, the sticker around the on button and volume control has to be taken off[15]. I also found that it was necessary to remove the glue holding the cables onto the case because the cables weren't long enough to remove the circuit board otherwise[16]. The potentiometer[17] needs to be desoldered in order to open it properly. A cable is glued to the circuit board right beside the potentiometer, with the glue partially covering a solder joint, so that also needs to be broken off[18] (yes, I accidentally touched the cable with my soldering iron). Once the potentiometer has been removed, it can be opened[19], cleaned, and greased, as already described in my previous article[0]. I also bent some of the contacts in the potentiometer outwards a bit so they would make better contact with the resistive surface, but I don't think that was really necessary. It also is somewhat dangerous because accidentally bending the contacts sideways could cause them to touch the wrong resistive surface (or none at all). I also removed the back which is held on by four screws[20]. This wasn't necessary to access the circuit board, but I didn't know that in the beginning, so I removed it anyways. As it turns out, this was a stroke of luck because it led to me finding another issue. The transformer is held on by two screws[21], although one of them is hidden underneath some foam[22]. When I had unscrewed those screws, I noticed that the plastic holding the transformer was broken on one side[23]. I glued that back on using two-component epoxy[24]. If I remember correctly, I did hear some sort of rattling noise when I first tried the speakers. I can't say for sure, but this may have been caused by the loose transformer. There shouldn't be any safety issues even if it breaks off again since it still wouldn't be able to touch any other components because of the way the speakers are constructed. Finally, I added some silicone glue as a replacement for the glue that had originally held the cables in place[25][26]. I used some neutral-cure silicone glue that I also use to glue on large capacitors since it shouldn't damage the circuit board. I think the most important part is the glue holding the cables to the outside of the case because that prevents the cables from being pulled out accidentally (of course, there are better ways to fasten cables, but those would be more expensive, so glue is used on cheaper devices). Also, don't forget to add the sticker over the on button and volume control again[27]. Bonus ----- I recently got some headphones that had a bad cable around the plug, as is normal for these devices after they've been used for a few years. After replacing the plug with a part from my audio cable collection, they work perfectly fine again, they just don't look perfect because I only have black heat-shrink tubing and the cable is white[28][29]. This was just a basic cable repair, but I still wanted to throw it in to show how simple many headphone and speaker repairs can be. Cable repairs aren't really my favorite, mainly because they are sort of boring, but I find it kind of ridiculous how many headphones and speakers I've saved from the trash just by replacing cables. Conclusion ---------- Even though I tried to show some of the more interesting speaker repairs in this article, they still weren't really all too exciting. I guess the main point was to show how many speakers and headphones end up in the trash because of relatively simple problems. That applies even more to the headphones I briefly mentioned and all the other speakers and headphones I didn't mention at all because they only had cable problems. It's just sad how much is thrown away because it's cheaper to buy something new than it is to repair the broken devices, even when the problems are as basic as broken cables. [0] gopher://lumidify.org/0/phlog/2023-10-15-speakers.txt [1] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers1.jpg [2] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers1_plug1.jpg [3] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers1_plug2.jpg [4] gopher://lumidify.org/I/phlog/2025-03-31-speakers/cable_soldering.jpg [5] gopher://lumidify.org/I/phlog/2025-03-31-speakers/cable_heatshrink_tubing.jpg [6] gopher://lumidify.org/I/phlog/2025-03-31-speakers/cable_heatshrink_tubing_shrunk.jpg [7] gopher://lumidify.org/I/phlog/2025-03-31-speakers/heatshrink_tubing_cut.jpg [8] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers1_volume_control.jpg [9] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers1_bottom.jpg [10] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers1_disassembly.jpg [11] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers1_capacitor.jpg [12] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers1_circuit_board.jpg [13] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2.jpg [14] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_bottom.jpg [15] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_sticker.jpg [16] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_cable_glue1.jpg [17] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_potentiometer.jpg [18] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_cable_glue2.jpg [19] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_potentiometer_open.jpg [20] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_back.jpg [21] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_transformer.jpg [22] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_transformer_foam.jpg [23] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_transformer_broken.jpg [24] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_transformer_glued.jpg [25] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_cable_glue1_replaced.jpg [26] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_cable_glue2_replaced.jpg [27] gopher://lumidify.org/I/phlog/2025-03-31-speakers/speakers2_sticker_reattached.jpg [28] gopher://lumidify.org/I/phlog/2025-03-31-speakers/headphones.jpg [29] gopher://lumidify.org/I/phlog/2025-03-31-speakers/headphones_cable.jpg