Soldering help on speaker repair gone bad - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 8 Old 09-30-2019, 04:36 PM - Thread Starter
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Soldering help on speaker repair gone bad

I have been trying to repair a speaker hum by diagnosing/replacing filter capacitors, described in this thread: https://www.avsforum.com/forum/89-sp...subwoofer.html

In the process of removing the capacitors, I believe the copper sleeves in the PCB's through-holes came out with the capacitor leads. Now the problem is worse.

I tried filling the hole with solder, but this is not working: the solder clumps to one side or the other side of the PCB but does not stay inside the hole.

My multimeter indicates that the resistance between the two sides of the same hole was in the order of megaohms for one hole(and essentially zero for another hole that I played on for a long time). That's without the capacitor installed. When in place, the large capacitor with snap-in leads does not allow access for measurements from the top side.

I don't know if this is part of the original problem, but it surely can't be helping. Also, I worry that I may have damaged the PCB or circuits by spending way too much time on it with the soldering iron, which is a basic non-temperature-adjustable one, and which has a fine tip that has been frustrating to work with.

1. How can I make sure to have good contact between both sides of the PCB holes missing their copper sleeve?

2. How can I check if there is PCB damage?

This repair has been getting increasingly frustrating, so any tips are really appreciated.
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post #2 of 8 Old 09-30-2019, 05:17 PM
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Get some solder flux and brush it onto everything you want solder to stick to. Then remelt the solder. It works like magic.
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post #3 of 8 Old 09-30-2019, 06:03 PM - Thread Starter
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If the hole is just PCB substrate, wouldn't it still not stick?


I got a box of rosin, which initially seemed to help with soldering in general, but it started leaving nasty black or brown residue that is very difficult to remove. The hot soldering iron just moves it around, but I can't get it off by scrubbing with alcohol. So, I stopped using it as it creates a mess.


I was chipping small (tiny) flakes and putting them where I wanted and using the iron to melt them, or melting a bit in the box and dripping it onto where needed. I noticed the cardboard box got blackened, and I wonder if the rosin got contaminated with carbon deposits.


The box of rosin looks something like this:



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post #4 of 8 Old 09-30-2019, 08:47 PM
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A small piece of wire man. Solder it to one side, bridge it across and solder the other. Takes 20 seconds and works great. I use that all the time in a pinch.

Blasting brown notes for 10 years and counting!

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post #5 of 8 Old 09-30-2019, 10:00 PM - Thread Starter
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What do you mean by bridging across? Passing the wire through the hole, or around the board? Either way it will interfere with the capacitor, which normally sits flush on the board. Still this might be worth trying.
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post #6 of 8 Old 10-01-2019, 02:24 PM - Thread Starter
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Thank you @N8DOGG ! Soldering wire between the top and bottom holes (passing around the board) got my speakers working again.

The solution is really sketchy as the 18 AWG wire keeps the capacitor far from flush with the board. I was also concerned that the soldered wire on the top could come undone without me being able to see it with the capacitor in place while soldering at the bottom. I'm not too confident of the connections but at least the result is that I have regained the use of my speaker! So it's confirmed, losing connection between the top and bottom of the PCB hole isn't good.

Despite making a bit of a mess, it is strangely satisfying to solve my own problems (partly by necessity, repair shops won't deal with PC speakers), even if I created half of them myself.

Now I'm back to the original speaker hum problem.
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post #7 of 8 Old 10-01-2019, 04:04 PM
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Quote:
Originally Posted by fizikz View Post
Thank you @N8DOGG ! Soldering wire between the top and bottom holes (passing around the board) got my speakers working again.

The solution is really sketchy as the 18 AWG wire keeps the capacitor far from flush with the board. I was also concerned that the soldered wire on the top could come undone without me being able to see it with the capacitor in place while soldering at the bottom. I'm not too confident of the connections but at least the result is that I have regained the use of my speaker! So it's confirmed, losing connection between the top and bottom of the PCB hole isn't good.

Despite making a bit of a mess, it is strangely satisfying to solve my own problems (partly by necessity, repair shops won't deal with PC speakers), even if I created half of them myself.

Now I'm back to the original speaker hum problem.
Nice! It may not be pretty sometimes but hey, if it works, it works! Lol

Blasting brown notes for 10 years and counting!

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post #8 of 8 Old 10-01-2019, 04:31 PM - Thread Starter
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Originally Posted by N8DOGG View Post
Nice! It may not be pretty sometimes but hey, if it works, it works! Lol
Yes, and even better, if it breaks, I know where to look.
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