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MP3 player repair for a beginner

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fractal5

New Member
I have an MP3 player that I really like, they are not made any longer. What is good about it is the ergonomics and user interface which is designed to be used by tactile feedback while the thing is in your pocket, not the capacity.

Over the past years it has started to get a poor connection with the 3.5 mm TRS audio jack. I would twist it a few times, add moisture, and it would be good enough to use it for a while. Finally I had enough and thought I'd try fix this myself. The device has two such 3.5 mm audio jacks (one for audio in, one for audio out), I never use the audio in, so I would swap the two, and use the "good one" for audio out.

I assume that most or everything that I'm doing is wrong and can damage the components in some way or do some other harm, so don't do this yourself if there are anyone on this forum that knows less about this than I do. So this is what happens when a beginner tries to fix his own MP3 player. I set my soldering iron to 320 degrees centigrade and get to work.

Problem 1:

The TRS components are soldered firmly in three separate places. How do I remove it? I cannot just put the soldering iron to one solder spot and pry it off, it is too firmly kept in place by the two remaining solder points.

My solution:

Remove as much solder as I can from all of them, then heat up one point and carefully pry it away from the PCB at that heated point. Repeat and rinse for each of the points.

Problem 2:

My solution to problem 1 resulted in a torn trace leading up to one of the TRS components, of course this happened on the side that I need to use for audio out, so this must be fixed.

trace_torn.jpeg

Problem 2:

Fix the torn trace.

My solution:

I use a scalpel to grind down to the copper under the solder mask. I use a very fine wire I harvested from some unrelated component to solder onto the now shorter and exposed copper on the torn trace. The other end is soldered directly to the TRS component. I check for continuity and it checks out OK.

trace_repaired.jpeg

Problem 3:

The picture above was taken before the final adjustment to this, and doing this final adjustment I managed to remove the adjacent small resistor. Then I discovered that during my procedure to remove the TRS components in the first place I had managed to knock off two other resistors!

The following three resistors outlined in red needed to be replaced (notice that one of them is in place in this picture, but it also needed to be put back in place).

resistors_knocked_off.jpeg

My solution to problem 3:

I have no idea how to do this, nor do I probably have the equipment for it. I imagine I destroyed the resistors using this "procedure" that I thought of myself.

These resistors are so tiny they are hard to even pick up. I prepare the solder spots on the PCB (excuse my terminology) with small globs of solder. I "attach" one end of the resistor to the soldering iron, push the other end gently into one of the solder spots on the PCB. At this point it is so hot that it melts that little glob of solder and "sticks" to that spot. The other end is then gently brought down into the other "solder spot". Since it melts both ends I found that it thankfully sticks more readily to these spots than to the soldering tip, hence it "lets go" of the soldering iron by itself using this procedure.

The end result:

resistors_resoldered_on.jpeg


Does it work? No.

Still disassembled but given power it powers up, seems to work, but there is no audio whatsoever.

I measured the resistance in the resistors while still attached, they are all the same, 0,7 ohms I believe. But note that this is measured while they are still attached to the PCB, which I believe gives inaccurate results? It was hard getting them in place so I would like to avoid taking them off again just to measure.


How should I proceed from here? Have I destroyed these resistors? I have an inexpensive digital oscilloscope and some other basic tools.

What did I do wrong in getting this far? How am I supposed to get those resistors back in place without doing it the way I did?
 

4pyros

Well-Known Member
Most Helpful Member
The problem may not be the jack at all.
You need to find the audio amp before the jack and check that its working.
 

fractal5

New Member
The problem may not be the jack at all.
You need to find the audio amp before the jack and check that its working.

You mean this component has been damaged by what I've done? Keep in mind everything was working before I did this, except for the slightly bad connection.
 

fractal5

New Member
What would the "audio amp" look like on such a tiny MP3 player? Is there another term for it? I don't find much of interest when I just search for "audio amp".
 

4pyros

Well-Known Member
Most Helpful Member
What would the "audio amp" look like on such a tiny MP3 player? Is there another term for it? I don't find much of interest when I just search for "audio amp".
It should be a chip tied to the socket.
 

atferrari

Well-Known Member
Few days ago I learnt that jacks could come with many combinations(and I mean MANY) for the three terminals. You should check if any of them has a connection that closes / opens when the TRS plug is inserted / extracted.

Most probably they differ.
 

4pyros

Well-Known Member
Most Helpful Member
Few days ago I learnt that jacks could come with many combinations(and I mean MANY) for the three terminals. You should check if any of them has a connection that closes / opens when the TRS plug is inserted / extracted.

Most probably they differ.
Thats mostly for switching from speakers to headphones.
 

atferrari

Well-Known Member
Here you have something to read
 

Attachments

  • Jacks some possible output combinations.pdf
    124.8 KB · Views: 175

tomizett

Active Member
You won't get a reliable reading of a resistor in-circuit, but it's often good enough to let you know the component is what you expect. 0.7 ohms is incredibly low though (as in you'd never measure it accurately with a normal meter) - do you think you could have a solder bridge shorting the resistors you replaced? Maybe they're not even resistors - you do get little surface-mount chokes in tiny packages.
I'd check what's going on there, and probe about with your 'scope to see if you can find anything that looks like audio.
 

fractal5

New Member
I figured it out.

(Edit: Thanks for the help and suggestions anyway guys!)

This is embarrassing but the TRS connector which I thought was the audio out was actually the audio in. After I soldered in place the connector in the correct position everything works great, despite my mistreatment and extreme heat exposure of the resistors.

But I'm surprised no one wants to tell me how many things I've done wrong?

I'd like to learn something from this so I'm curious what is the correct procedure to do these things? Especially what is the correct way to solder back in place those tiny resistors -- I thought I'd never get them back in place without some kind of reflow soldering.

Since I don't own any fancy equipment nor really know how to use it (except having seen the odd video on how to do this), what is the "poor man's" equivalent of reflow soldering, such as how do you do it in this case specifically?
 

tomizett

Active Member
I find soldering them back on is not too hard - just hold them down with some tweezers (or blu-tacked to the end of a pencil) and tack one end. When you're happy with the positioning, solder the second end and them move back and re-do the first end tidily. If you're not already using them, I find sepperate flux (ie, additional to what's already in your solder) and solder braid/wick are great friends in SMT work.
Getting the bug*ers off the board is usually where it goes wrong for me. You can try flooding several pins (of an IC) with solder and leavering up one side at a time (risks lifting tracks tho), or using two soldering irons as heated tweezers. I've also seen people using (what appeared to be) a gas soldering iron with the tip taken off as a hot-air gun. If you're sure you've got a dead IC, you can chop the leads off with a knife, lift out the package, and desolder the leads at your leasure. The issue is compicated when you've got components that are glued down under the package as well as soldered.

I don't think there's an easy way really. When I'm king I'm going make surface-mount illegal, along with multi-layer boards. Might just dictate everything must be on tag-strip...
 
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