Audio jack soldering problems + general questions

Thread Starter

rambomhtri

Joined Nov 9, 2015
319
Hi, I'm having problems fixing a headphone's jack connector (replacing it). First I bought a nice jack from Neutrik:
1.jpg 2.jpg

...to replace the jack from a good pair of headphones, $50 wort. So I wanted a good jack connector, that's why I bought a Neutrik connector (like a month ago). Well, I soldered the cables and it worked flawlessly for a week or so. Then, one day, suddenly, the left headphone stopped working, and I was shocked.
I soldered it myself, how it could be that a manual soldering had broken in just a week!
I expected it to last for years. I tried the headphones in my mobile, then in another mobile, same problem. Then in a PC, and suddenly, worked again. It's lasted another week without a single problem, until a few days ago when it started to happen the very same problem. So, I disassembled the jack connector and checked the soldering joints and the jack's different parts with my multimeter. It was in "beeping mode". And there it was, it beeped when I touched the left channel in the jack (tip) and the ground pin (copper). I thought the jack connector was defective, so I thrown it away.

I ordered another one, but meanwhile, I had these $10 headphones I wanted to repair too, so I used a chinese jack connector:
3.jpg

I burnt the cables, and you know, all the process I did with my expensive headphones. After all was done, before trying them out, I checked the connections with the multimeter. These are the measurements:

Left channel in jack (tip):
To ground pin (copper): 17.6 ohm
To left headphone pin (green cable): 1.0 ohm
To right headphone pin (red cable): 34.4 ohm

Right channel in jack (middle):
To ground pin (copper): 17.6 ohm
To left headphone pin (green cable): 34.4 ohm

To right headphone pin (red cable): 1.0 ohm

Ground in jack (upper):
To ground pin (copper): 1.0 ohm

To left headphone pin (green cable): 17.6 ohm
To right headphone pin (red cable): 17.6 ohm

So, what I expected to be completely isolated, is actually just 17 ohms, or 34 ohms. Nevertheless, I tried out the headphones and they worked just fine, I twisted them and all, but not a single noise or audio interruptions. I'm inspecting the connections and all, and they all seem pretty isolated and well joint. Here are some pictures:
4.jpg
5.jpg
6.jpg

The cables actually go through a hole and are mechanically attached to each pin. Also, these cables are coated with an isolating layer. I made sure this layer was burnt just before the solder joint, so even if the red, green and copper wires are touching, there's no electrical connection. You can clearly see the green coating in this last picture, that is there until the solder joint.

So, first question:

1. Why am I getting short circuits between the channels and cables if, as you can see in the pictures, all seems to be well isolated?
Is it a problem if I get than many ohms? How is it working anyway, if both headphones are touching ground?
Would a well done job at this have infinite ohms between the cables?

2. The metal clamps avoid the joint receiving all the pull in case of a cable pull. How do you really clamp it? Is there a guide or something? Or you just press with a pliers the most you can and that will do it?

And finally, I want to know if I'm using my soldering iron correctly. After 13-15 times used in a year aprox., this is how it looks:
7.jpg

3. Is it alright? Is that black zone indicating I'm not using it correctly (not tinning it well or heating it up too much)? Or that black zone is normal?

I try not to over-heat it, and always put it at minimum temperature when I'm not using it. But I'd like to see the opinion of an expert and tell me if that's a good maintained iron tip. The black zone is over the white layer, solder won't stuck in the black/white zone.

Thanks!
 
Last edited:

GopherT

Joined Nov 23, 2012
8,012
You should "tin" your wires before soldering them to the device. Tinning is melting a bit of solder into the wires to wet all of the strands with solder. The little bit more solder added to bond the tinned solder to the device will make a much better joint. Do not add more than necessary when tinning. If you add too much you will feel that solder wicked up the insulation and made the wire stiff - then you create other issues with the wire breaking during use (since it is no longer flexible).

Also make sure you have a good bond to the headphone jack. Some are still wet with processing oils or heavily chromed so solder doesn't stick well. Clean with alcohol and, after it is dry, Heat sufficiently to get solder to "wet-out" onto the Jack - solder beads are bad.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
319
Thanks for the general tips, I appreciate it. I forgot to tin the cables as well, you're right and I will do it in the future (I did in the past, but this time I forgot it), although if I had, it would had been very difficult since we're talking about very, very tiny cables.

Nevertheless, I'm looking for a more specific answer to my 3 questions, that's why I numbered them, so I can get and answer to each one specifically.
 

Tonyr1084

Joined Sep 24, 2015
5,213
Answer #1)
From your measurements it would seem that if you are measuring between the tip and ground you're measuring 17Ω through the headphone speaker. Unless you're measuring BEFORE you add anything to the jack - it can't be anything else.

Looking at your solder joint I see a lot of loose wires. That's probably why GopherT suggested pre-tinning your wires before soldering. Pre-tinning the connector is also a good idea. And like GT said, avoid excess solder because it will wick up the insulation and create a brittle condition where just about any flexing will break the wire internally (inside the insulation) in as little as a day, a week, a month. Depends on how much you flex it.

Answer #2)
The "RIGHT" way to crimp that metal support is to use a tool specially designed for that purpose. I've NEVER owned one of those tools, they'd be expensive and I'd use them less than 10 times in my lifetime. Usually you just pinch them over to support the wires. But be careful not to pinch them too tightly or you can pierce the insulation and cause a short.

Answer #3)
The black on your soldering iron is normal. However, when in storage (idle heat or put away) it should be kept tinned with solder to prevent oxidation.

Tips DO wear out. The more you use them the more they sublimate (loose their metal). Soldering is a process that occurs at a molecular level. It's like plating, where metals migrate from surface to surface. Given the nature of different flux chemistry, tips may last longer or shorter - depending on the aggressiveness of the flux.

There are cleaners and tip restorers you can use to help keep the tip in good condition. I don't have any recommendations but I do use a steel wool sort of material that looks like brass. I don't KNOW that it's brass, that's just what it looks like to me. I'm certain others can give you a better answer regarding tip maintenance. For now the best I can give you is to keep it tinned when idle or in storage. More so when idle (hot but not in use).
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
319
Oh, wait, so I'm measuring the actual resistance of the headphone itself?

All the measurements have been taken after the replacement us finished, everything is soldered correctly.

I thought between the tip/middle and the ground there should be a lot of resistance, so the headphone is not shorted.

So let me get this right.

If there are 15-20 ohms, the connection is OK.

If there are 1.0 ohm or so, there's a short circuit BEFORE the current reaches the headphone, so that headphone won't work since the current is going through another path.

If there are a lot of ohms, or infinite, it means the connection is really bad done, or even there's not connection at all. The headphone won't work either, or it will be really low in volume.

Am I right?

So, with my previous headphones which left headphone didn't work, I was in case 2, there was a short circuit BEFORE the current could go to the headphone.

Right?
 
Last edited:

GopherT

Joined Nov 23, 2012
8,012
Left to ground will be about 16 ohms, right to ground will be 16 ohms and left to right will be 32 ohms.

Assuming 16 ohm impedance headphones. Also, you can expect values to range from 12 to 24 ohms.
 

Tonyr1084

Joined Sep 24, 2015
5,213
17 ohms across the speaker is good. less than 1 ohm is a short and very high or infinite resistance is an open (broken or disconnected) line. Keep in mind it's also possible to have a soft short (not a complete dead short) where you might read 2, 3, or 5 ohms (numbers are arbitrary). Like GT said, it's normal to see resistance (through the speakers) of 12 to 24 ohms.
 

Tonyr1084

Joined Sep 24, 2015
5,213
The last photo in your first post - you show the metal tab being pinched on the wires. BE SURE TO SOLDER THE WIRE BEFORE YOU PINCH IT. Otherwise the heat from soldering can easily pierce the insulation and cause a dead short. Again, don't over pinch it.
 
That thing you bought is actually a plug.

There may be an issue with the shield preparation. See: http://www.radiomagonline.com/deep-dig/0005/braided-shield-cable-preparation/26116

Fanning the shield out makes a weak connection. You need to pull the wires through a hole in the shield. Hopefully it's possible in this case.

I'm also thinking heat shrink tubing, but not sure. You can get heat shrink with an adhesive.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
319
That thing you bought is actually a plug.

There may be an issue with the shield preparation. See: http://www.radiomagonline.com/deep-dig/0005/braided-shield-cable-preparation/26116

Fanning the shield out makes a weak connection. You need to pull the wires through a hole in the shield. Hopefully it's possible in this case.

I'm also thinking heat shrink tubing, but not sure. You can get heat shrink with an adhesive.
Sorry, I don't understand what you say. My cable had 4 wires, ground left, ground right, right and left. First, I burnt the coating of each single cable with a lighter, and tested the continuity in the "naked" segment. That guarantees I've removed the isolating coating in the part of the wire I'm gonna solder to the pin.

I joined the grounds and then pass each cable through their respective hole in the pin, and solder them.

What that has to do with your reply?

Thanks.

PD: now I know I should have tinned the cables before passing them through the holes.
 

be80be

Joined Jul 5, 2008
2,049
From the looks of your pictures the wires have reinforcement hairs in them I don't really no what it's called but it's some kind of fiber to make the wire stronger. It can cause problems like cold joints if not pre tinned and you crimped the wire you can see it got hot headphones that plug in small jacks have harder cables to solder because of the needed reinforcement to make a strong cable.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
319
This http://www.radiomagonline.com/oldradimage/images/archive/eng_wire_spr03_detail.JPG pic in the above link shows how to make a hole where you pull the inner conductor insulation through.

This leaves an intact braid.

There are thermal strippers http://www.omega.com/pptst/TW_TWC_STRIPALL.html where a small area is heated and then the insulation is pulled off. Stripping fine wires is very tough.

I do agree, tinning in this case would probably help.
But the cable of my headphones have nothing in common with that shielded cable you're talking about.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
319
From the looks of your pictures the wires have reinforcement hairs in them I don't really no what it's called but it's some kind of fiber to make the wire stronger. It can cause problems like cold joints if not pre tinned and you crimped the wire you can see it got hot headphones that plug in small jacks have harder cables to solder because of the needed reinforcement to make a strong cable.
When I remove the isolating coating with fire (a lighter), I burn both isolating coating and that white fiber that's along the cable.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
319
Wooooooooooooooooooooooooooooooooooooooooooooooooow, finally!

I've finally fixed the expensive headphones with the Neutrik plug, I'm so happy, thank you all, I think what really helped me was the tips about tinning the cables, that I think made the difference between instable & weak joint and a solid & good one. Although those little tiny mother EF's didn't want to be electric conductors, it was so hard to tin them. As I was kind of exhausted, I didn't take a picture of the final result, sorry, I forgot it. These are the measurements:

Left to right: 37 ohm
Ground to left: 20.8 ohm
Ground to right: 18.7 ohm

A quick question here, that difference in ohm between right and left headphones, will it be perceptible?

It's a 15% of difference in ohms between right and left headphone, does that mean that I will hear the right headphone 15% louder than the left headphone, or not necessarily?
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
319
I've tested it with my sound meter (cheap one but it's what I got) and both headphones seem to deliver the same amount of decibels. I don't understand this.

Shouldn't the 20.8 ohm headphone "consume" more voltage than the 18.7 ohm in order to have the same current?

In other words, the 20.8 ohm headphone should need more power, so that should have to make a difference in the decibels delivered by each headphone.

Does anyone here know the answer to this?
 
Since P = V^2/R,

Make V^2 = 10 arbitrarily and use 10/20.8 and 10/18.7, the difference in power will be a lot less. e.g. 5% or so. Add the inaccuracies of your measurement and I think it comes out in the wash.

With speakers, I'v only cared about two things:
Are they Open?
Polarity = Pushing in the same direction
A proximate Resistance.
 
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