I have a fever history of 10+ years in my headphone. I haven't lost my fever and re-entry pits for a few rounds. The pit first year started around 2005 when I started es5 and a8. (It is said that the jump pit is a fireball that jumps into the headphones. Headphone pits, these two are good goods), but really concerned about earplugs headsets have already started from around 2002. At that time, I was still in college. I couldn't afford a headset that was more expensive than the mx500. The goal of that year was to wear a headset or an earhook, including Koss PortaPro (Koss PP or PP). Koss PP is a fossil-grade portable earphone with a history of more than 30 years. The styling of listing in 84 years should be pretty cool and cool, but now it is absolutely retro cool. In terms of sound quality, the evaluation of senior veteran vineland and Xiaobai is relatively positive. So in the third pit, when the "collective mind" collection series was established, pp and ew9, esw9, k314p, and form2i were bought back together, probably around the year 2011. PP feels after the hand is "not worth!" As long as the shell is a plastic structure, I do not know is the texture of such a bad plastic, color enamel in the light blue enamel ... ... look good pictures, but look at the physical feel this blue More emphasis on low-cost plastic feel seated. Wearing it is better than the hd25 and dt1350 that were in hand at the time, but there is still a sense of discomfort when the buckle is adjusted to the loosest position (for reasons described below). Sound quality... After having hd25 and dt1350, pp's voice is obviously sticky, and there is no music type suitable for listening to it. In this way, pp came to the back of the hand for a long period of time, for the sake of washing my clothes, when I was cooking, IpC or iphone usually wore household chores. Because it is not soundproof, the daughter told her father to hear urine or wife Hedong can hear; more because it is cheap, feel when working, when washing clothes, accidentally when the line into the soapy water, do not have to feel bad. So, one day, when he got up and washed his socks and got up, the knee caught the line and raised his head and pulled the line fiercely... My deity, the R-side cord completely pulled away from the unit. At this time, I feel, feel bad! Still will feel bad! ! ! After the pain has finished, we must continue. The first idea at that time was to find a place to repair. However, in today's era of brand new products, most of them are fast-failing products, maintenance headsets (even a lot of mp3) have become economic benefits, and even in the electronic city can not find the headset repair shop . Taobao found a repair shop in the same city, asking price 150 or 200 forgot. Three hundred dollars of headphones to spend 200 repair? After I finished the price, I said a thank you and silently closed the dialog. It is better to ask for help, but it is to break the line and weld it back. I did some homework under the net. After learning the tools and basic steps of welding, I found welding tools on Taobao. A good seller gave a detailed welding video demonstration link in the product description. I thought after reading it a few times, I should have done it. Although I was a liberal arts student, although I hadn't touched the welding rod, although I had a black history of tearing down a few mp3s that wouldn't go back. In Taobao to buy a good tool, I picked the dark night of high winds, quiet, waiting for his wife and daughter to fall asleep, so that if welding a small fire or to cause any short-circuit trips or meditation. Without any worries, I began my life's first welding attempt. The results really made me into the following simple description with the map. The first step is to remove the sponge. Note that there are barbs (?) on the unit. When unloading the sponge, it is necessary to gently hold the edge of the sponge slightly to mention it, and then carefully remove it. After removing the sponge, it can be seen that the unit and the housing are only connected by a small button in the center, the structure of the button cannot be seen clearly, it is fixed securely, and the unit can be provided with enough flexibility to adjust the wearing angle. There is a plastic clasp on the unit that is carefully removed to reveal the cord and solder joints. In this way, the removable parts have been separated. The design of the entire headset, do not know how to describe, rough? Simple and crude? The second step is to start welding the regular dishes. First, the solder rod is heated to melt the tin spot, and the tin residue is removed with a solder absorber. The only comfort was that both units were speaking and did not hear the sound. 12V100Ah Lithium Ion Battery,Deep Cycle Solar Battery,2V 100Ah Lifepo4 Battery,12V 100Ah Lifepo4 Battery Pack Jiangsu Zhitai New Energy Technology Co.,Ltd , https://www.zhitaibattery.com
Roughness is not allowed, PP sponge as long as a little aging, unloading a little harder will tear up the sponge, as shown. 
Then, the tip of the headphone cable is burned to a length of about 0.5 cm of rubber, and the copper wire is exposed, and then the copper wire is rewelded. It's not hard to say. It actually took me half an hour. The difficulties here are: 1. Keep the tilt angle of the unit so that there is enough space between the housing and the welding point; 2. A hand-held welding rod to control the temperature; 3. Fix the position and shape of the copper wire; To provide a good viewing angle and operating position for the welding, the earphones can not be operated freely on the table and must be fixed by hand. To sum up, the operation feels that the two hands do not use or have too few fingers. It is recommended that before the start of work, there should be no more drills or drills, or be called a basic friend or operate with a fixed instrument.
After working hard for most of the day, I finally rewired the headset cord. The solder joints were not worth mentioning, and the edges of the plastic shells were also burnt out with several dog teeth. 
Finally, the plastic buckle can be placed on and put back into the sponge cover. Try again, the sound is not biased.
In this way, the bumped headphone repair function achieves the target recovery goal, scores 5; the appearance of non-destructive goals is not reached, scores 2 points; skill tree development, score 4; achievement satisfaction, score 5 (yes, it is full of inflation ); Comprehensive score (5+2+4+5) 4=4 points.
In the process of repairing this broken line pp, the unexpected harvest was rediscovered on all aspects of this paid headset. Before the hands-on repair, I tried to find the relevant structural diagrams and explosion maps of the pp on the Internet. I inadvertently found a picture of wearing it before I discovered that I had always worn the right and left ear. Here again posted: 
After wearing correctly, the problem of wearing discomfort that has been bothering me has been greatly improved. When the ear unit is pressing on the ear, the stress point is more in line with the head and the ear hole, rather than the pressure on the pinna when it is wrongly worn. Because of this "accidental" discovery, the time allocated for listening to PP was much longer than before, and I also had more attempts to adapt it to music and equipment. Its low resolution, I think, provides a non-stimulating sound of resistance. It's true that the volume is slightly lower and the potential is not deep, but with some warm and enthusiastic music types, such as European and American pop, country music, the sense of atmosphere comes up, and the sense of hearing is not bad.