Fixing my AKG 240 Headphones
I've had a pair of AKG K 240 headphones since 2000. A friend had them for years, and he gave them to me when he moved away. If you don't know what they are, just look at just about any video of someone recording something in a studio. If they're wearing a pair of headphones, 9 times out of 10 it's a pair of these. They are perfect for sound isolation. They are famous for their comfort, the pure fidelity of their sound, and their legendary durability. But my kids can damage just about anything. That long cord got beat to death and they quit working.
These are proper equipment. The leads are soldered onto proper posts - no stupid plastic tabs or twist-locks in here. The wiring is properly insulated and wrapped. They're meant to be fixed. But it's very difficult to find a place that will do this sort of electronics work. With the advent of the buy-it-cheap-and-replace-it market, shops are few and far between these days. I kept them just because they're the kind of thing it's worth the money to fix, but over the years it got shuffled off the plate many times and I made do with "good enough" over and over.
The Koss full-cups that I've been using for the last several years were okay (especially since they only cost me like $20 on clearance) but they have picked up a nasty buzz and a couple days ago the straw finally landed on the camel's back. I had reached the point where it was worth the risk of me screwing up to try to fix the AKG's myself. So I headed for Radio Shack and bought a very nice extension cable, intending to behead it and use it to replace the cord.
The pair I have are at least 15 years old, and the model has been updated a couple times since then. Looks like the the closest you can get these days are these. A little research showed I'm not the only one who has had a similar problem. As you can see, the newer ones have a jack system in the headset that allows you to just unplug and put in a new cord whenever you wish without having to get out the soldering iron.
Genius! When I saw those pictures with the break-away cord a light went on in my head. I know the jack itself is fine; it's breaks in the cord itself (you could literally see the separate wires through damaged shielding in several spots). So, if I hack a foot or so off the male end and solder THAT onto the posts in the cup, then I can use the extension for it's intended purpose and just replace the cord when/however I wish. So that's what we did.
I looked all over the internet and didn't find any good, clear instructions for this. And they would be less helpful than you think anyways. AKG changed the particulars inside several times over the course of the run. Not just a little bit - completely changing the way the cup goes together so if you try to follow some of the directions you'll break things sort of different.
Now that I've fumbled my way through it with the help of my elder son, here's how it went down for us.
1. Ready Your New Cable
I prepared what would be the new cord by snipping 8" or so of the end off the old, damaged cord. Using strippers, carefully cut away the loose casing to expose an inch or so of the three individual wires inside it without damaging their insulation. Strip away a good half inch off of the casing off the inner wires and trim the ends even.
2. Open the Earpiece
There are two ways to get into the cup, and here's how to tell. Take the leather and foam ring that fits around your ear off (it just slides off the plastic), and look inside. If you're looking at a loose circle of foam with what looks like very thin, translucent fabric glued in underneath, just slip the foam ring back on. You're coming at it the wrong way. (If it looks like anything else, Google around and you'll find instructions on how to get in there.)
If that's what you see, here's what we had to do to take it apart:
- Turn the cup over and you'll see a brass-colored circle with the model number on it. It's just glued down. Pry that circle up by putting a tool in the small notch in the left side of the plastic casing for leverage. Try using a small screwdriver (I used a fine knitting hook). Some people recommend getting a heat-gun to warm the glue and make it less likely to bend or damage the plate but I didn't need it. Just be careful not to warp or scratch it.
- Underneath it is a tiny screw with the weirdest head you've ever seen -- looks sort of like a snowflake carved into the top. Just use a small Phillips head and take it out. Then the black plastic plate will come up. Now you're looking at wires and interesting things.
- In the center is a much bigger screw (same screwdriver fits it). Remove that. At that point the wire headband will come free of the cup, and you'll be able to straighten the connection wires and see what's up.
STOP! At this point, take a GOOD picture of what you're seeing. As you can see by this one I didn't get as good a view of the wiring as I should and it made for confusion later.
There are three wires (red, white, and yellow), soldered to two posts on the corners of the plastic block that holds the wire band that goes over your head. Mark them so you can tell which one has the white one, and which the red and yellow ones (I wish I'd thought of this while doing the work.)
About half-way through trying to decipher my bad pic and figure out exactly what had been hooked to what, I found a webpage on their official website with tech-sheets for all their models, including the older versions in PDF (and it had English on it!). That put us on much more certain footing.
When you're wearing the headphones, the cup with the cord coming out is usually worn on the left to keep the cord out of the way of the neck of the guitar (but once you're done with this project it's entirely up to you). If you're following the diagram in that PDF, that one is marked with a big L, and that picture is laid out in reverse of how you'd wear them (don't get me started on that). If you're looking at the headset from that orientation, the white cord goes the front post, and the red and yellow wires are twisted together and both soldered to the back post. Or if you remembered to mark them you already know this. :)
3. Solder in the New Cord
Good soldering tutorials are all over the internet. I'm partial to this one, or just search on YouTube. Believe it or not, another good source for info might be your local craft/fabric store. There's a fashion these days to make jewelry by soldering and wrapping glass with metal. As long as you don't mind that some of your equipment is pink or flowered you can get some good deals.
If you have one, you're going to want to get out the Helping Hands for this. We had to get out both of mine by the end and that was with two sets of hands working on the project. Between the various wires, the band, and the cup you're going to need the help keeping things steady.
- De-solder the connections. Use a bulb or de-soldering braid to get the old solder out of there. At that point the cup will come totally free of the band.
- Now that it's loose, take the old wire and pull the plastic holder off the end that stuck over the edge the cup to steady it. Slip it over the end of your new cord on the end opposite the plug, pulling it firmly so it holds onto the exterior casing. Make sure all three ends of the interior wires are still sticking out and not under tension.
- Clean and flux the posts, the ends of the wires sticking out of the cup, and do the same to the cord wires.
- Solder the wires from the cup and the cord to the appropriate posts. Match them up according to the diagram in that PDF.
Still apart, but all the soldering done:
4. Test Your Work
There are several things that could still be going wrong here. To make sure it was working properly before I put the case back together, we carefully plugged them in and listened to them. Make sure it's a CD-quality recording, played on good equipment. You want to make sure there's even sound levels coming in from both sides with no hums, buzzes or other unpleasantness. If you tested with some thrashing mess your kid recorded off YouTube you might not know if it's the hardware or the music. ;) Push the whole range with a variety of sounds if you can. I used a vinyl recording of Mel Torme, a live recording of Journey, some Chopin, and a Skillet song. If you're satisfied, go on to the next step.
If not, try de-soldering things and putting them back together again, this time being more careful of the cleaning and making even more sure of good contact in the connections. If that doesn't work, maybe the problem is in the wires through the headset band, or you may have to get into the even more arcane science of replacing the drivers in the cup themselves. Both are possible, but I would probably chicken out and get a pro involved at that point.
6. Put Things Back Together
- Fit the wires of the headband into their slots in the back of the cup enclosure, and center the block over the hole. Make sure it's upright - there's a part underneath in the cup that needs to fit in the right direction.
- Put that larger screw through the hole in the block at the end of the headband and make sure it screws down into the center of the bar arrangement inside the cup that lets it swivel.
- Put the holder on the end of the new cable into it's slot at the bottom of the cup, and make sure the connecting wires all fit in there without tension. Place the black plastic cap over them all, fitting everything along the appropriate grooves. It should fit flush all the way around. Use that tiny screw with the weird end to hold it in.
- Snap that bronze metal plate back into it's slot. The old glue might still hold it. If not, I just used a small touch of rubber cement. You don't want anything water-based, or anything that would make it impossible to get it back off without breaking it again.
Last step is to enjoy listening to your music clear as a bell all the way down to the bottom of the bass clef again. And maybe the next time I submit something to the GWJ podcast it'll be properly mixed and not make the sound guy weep.