Capacitor replacement

[Mike Richardson]

For those who have replaced capacitors on old Macs, did replacing the capacitors solve audio issues?

I have a Classic and an LC II that have audio issues. There are a lot of squealing noises and static but you can still make out the audio. I believe it is capacitors that filter the audio that have failed, probably the 50V capacitors for sound out and in. That is my theory, because I have not replaced the 50V capacitors yet on my Classic but I replaced 5 other ones with little or no audio improvement yet.

 

[iMac600]

Replacing capacitors often solves audio issues. I have an LC that "squeals" from the internal speaker while on, and replacing the capacitor fixed it.

 

[Flash!]

You can fix any piece of electronics if you replace every component on the board [)] ]'>

I've not looked at a Classic motherboard, but I figure that an audio circuit that's 20 years old is bound to have transistors or a simple 6 or 8 pin IC that you can replace. (Tip: I solder IC-sockets back onto the board so the same component can be repaired again later without have to use a soldering iron) I'd suspect almost every capacitor in the circuit would ba little tired and I'd probably just replace everything - even resistors, which are the most robust component usually.... but this is a 20 year old Mac. If it didn't work after that I may be forced to break out the multimeter [] ]'>

 

[tomlee59]

Having fixed more Macs than I can count, I can offer these (admittedly unscientific, biased-sample) statistics:

1) Bad semiconductors are almost never the cause of audio problems in these all in ones. In fact, I am unable to recall a single case.

2) Bad capacitors (and this includes the goop they can leave behind) are almost always the cause of audio problems in these all in ones.

3) The number 2 cause of audio difficulties, and it is a far-lagging second at that, is bad contacts on the headphone jack.

So, if my stats are at all representative of the larger population of bad macs as a whole, then a prudent troubleshooting strategy would start with an examination of the two common sources.

I have never needed my multimeter to fix any audio problem on these compact macs. Chances are that you won't, either.

 

[JDW]

You can fix any piece of electronics if you replace every component on the board

Take an Xacto knife and slice through a few traces on your logic board. Now replace "every component on the board." Does it now work? No. Why? Because "replacing every component on the board" does not guarantee 100% perfect "like-new" operation. In my own experience, I have found this to be true.

Why do I say this? Because I am a strong advocate of "replacing every electrolytic capacitor" on logic boards, especially the SE/30 board; but you must set out to do such work as a labor of love, keeping in mind there could be other problems that capacitor replacement will not solve. I have one logic board like that. All the caps were replaced and yet I get horizontal lines at boot, no chime, totally dead. But again, this should not faze those of you who need to fix problems with your logic boards. Replace the caps. But just keep in mind that there is a small chance it may not solve every problem on a really beat up board.

As to the question on whether replacing caps will solve audio, the answer is "yes, almost 99% of the time." And you need not replace every cap on the logic board either. Only the caps around the audio section of the board -- but I only state that for the chronic "lazy" among us. My father often told me, "when you do a job, do it right, and finish what you start." And so I give that same prudent wisdom to all of you. Despite the fact that the replacing of only a few audio caps will likely solve an audio problem, you should replace all the electrolytic caps on a given board, because there are likely other problems other than audio you are not yet seeing. And sometimes those problems only appear rarely and they seem not related to capacitors (like a crash now and then you cannot explain).

"But, JDW, I lack the knowledge, experience and tools to replace the caps!" I don't mean to offend many of you by saying this, but such remarks are a cop-out for not doing what you need to do! It's not as difficult as you think. But for those of you who have embarked on this soldering task and failed, then please know there are some on this site (yes, even in your own home country), who would likely do the work for you for a small fee (and of course, you would need to pay shipping both ways). But again, you can save more money by doing it yourself, and I can tell you from experience that it is not THAT hard. Plus, it can be a rewarding, educational experience, and may even be fun for you!

I may be an engineer, but I am by no means a "modder" or "hacker" or "lover of all things solder." I only set out to accomplish "the accomplishable." And because I know I am by no means the best solderer on the planet, I feel confident that "if I can do it, so can you."

Good luck.

 

[Mike Richardson]

Looks like I trashed the Classic II board.

I pulled off solder pads for one capacitor by mistake. Now the audio is completely gone. I had replaced every capacitor near the audio section except for one; if I had replaced the one successfully, audio would probably be working fine now.

The only effect on functionality is that audio is completely dead now, however, since audio was in effect useless before, it is not a huge loss. The Classic II was sold on eBay "as is" and I never stated the audio was working.

 

[JDW]

And...?

I am completely baffled how you could give up so quickly, in light of the work you already performed. So what if pads were ripped off? Pads come off. It's not a problem. I know because I've pulled them off my board even while taking great care NOT to do so.

You can clearly see to what locations those pads (and traces) lead to on your logic board. So run a couple wires from their origins to both sides of your cap and you're done. What wire? Any wire! It doesn't really matter at these voltages and current.

It really is that simple! Two pieces of wire and four soldered points and you're audio is back in business!

 

[Mike Richardson]

I'm going to look at it tomorrow. I'm not too sure how to attach the wire. It looks like the trace goes into a little hole on the motherboard. I can stick a wire in there, but how do I keep it there? Glue?

I have not given up. I am working on my LC II board now. I have replaced many of the capacitors, and the audio has improved greatly. The only thing that has stopped me is that I ran out of 10uf capacitors. Tomorrow I'll get some more and finish it up, and my LC II will be in perfect condition.

I just got in a Performa 550 with audio problems. It's probably going to need new caps. There's always an SE and SE/30 that need attention too.

Once you get the hang of it, it's not so hard. Getting - and + right is a little confusing, but I have discovered, that on all caps there is always a kind of darker or lighter line on one side, on the cap, and that's always the negative side. I've had no problems with that.

I will say it is a rewarding experience to be able to restore an old motherboard instead of letting it fail even more or trashing it.

 

[JDW]

Mr. Richardson, can you please explain to us how you broke these pads in the first place in light of the fact you clearly know nothing about "solder"?? And how did you replace those capacitors you say you've replaced? Glue? Indeed not. You used solder. Copper wire is made to be inserted into those "holes" of which you speak. And to affix that wire to those holes permanently, you simply use solder.

I'm quite confused by your last post, so perhaps you should explain to us more what is going on. Because I for the life of me cannot see why you are having trouble unless you don't understand solder. But again, if you don't know what solder is, then how did you replace those caps?!

Regardless, I can only add that any old DMM (multi-meter) with a continuity check feature will be useful to you in that it will "eliminate doubts" about where to wire something. If you have a doubt where one of those dislocated pads originally led, and if you cannot follow the trace with your eyes for some reason, you simply put one problem at the trace edge where the broken pad used to be and put the other probe where you think the trace originates -- in many cases, it could trace to multiple locations (any of which you can connect to, but the way). When you've found the origin, your meter will beep at you to let you know there is continuity between the probes. If your meter doesn't beep, you simply need to probe another spot. And once you've found the right spot, you just solder one end of a wire to that point. It doesn't matter if that point is a thru-hole in the PCB or a pin on an IC. Just solder one end of the wire there. Then solder the other end of the wire to the appropriate leg of your capacitor, making sure you get the polarity right. Do the same for connecting the other wire and you're done!

That's it!

 

[Mike Richardson]

Mr. Richardson, can you please explain to us how you broke these pads in the first place in light of the fact you clearly know nothing about "solder"?? And how did you replace those capacitors you say you've replaced? Glue? Indeed not. You used solder. Copper wire is made to be inserted into those "holes" of which you speak. And to affix that wire to those holes permanently, you simply use solder.
I'm quite confused by your last post, so perhaps you should explain to us more what is going on. Because I for the life of me cannot see why you are having trouble unless you don't understand solder. But again, if you don't know what solder is, then how did you replace those caps?!

Regardless, I can only add that any old DMM (multi-meter) with a continuity check feature will be useful to you in that it will "eliminate doubts" about where to wire something. If you have a doubt where one of those dislocated pads originally led, and if you cannot follow the trace with your eyes for some reason, you simply put one problem at the trace edge where the broken pad used to be and put the other probe where you think the trace originates -- in many cases, it could trace to multiple locations (any of which you can connect to, but the way). When you've found the origin, your meter will beep at you to let you know there is continuity between the probes. If your meter doesn't beep, you simply need to probe another spot. And once you've found the right spot, you just solder one end of a wire to that point. It doesn't matter if that point is a thru-hole in the PCB or a pin on an IC. Just solder one end of the wire there. Then solder the other end of the wire to the appropriate leg of your capacitor, making sure you get the polarity right. Do the same for connecting the other wire and you're done!

That's it!

I knew a few things about soldering, and I know a few more things now.

The first capacitor I replaced took about 30 minutes for me to do, in order to figure everything out and get the process down. I knew basic stuff like, heat up the metal (solder), etc. and I pretty much just figured it out. Now it takes 5 or 10 minutes to do a capacitor. I knew what iron to buy (a 15 watt one with a smaller tip, which is more suitable for these things) and some stuff like that.

Solder does not seem to affix to plastic. There is no metal left on the board for this particular capacitor except for what's inside of the little holes. Any solder I put there falls off because it does not affix to anything.

The pads broke because I removed the capacitor too aggressively. I cannot seem to remove them by simply heating up the pads because most of the pad is under this plastic stuff, so I have been rocking the capacitor back and forth gently until it breaks off, and then I remove the little metal bits it left behind from the little globs of solder.

 

[wally]

Five minute epoxy can be used to glue down an improvised replacement pad made out of copper foil or even the flattened end of a piece of bare or tinned copper wire, cut long enough to lap slightly over the remaining trace. Use only the smallest touch of epoxy. After gluing the epoxy will really set almost immediately with the heat from the subsequent tinning/soldering operation, but best not to use tip hotter than 700F. As long as the epoxy has not formed a bead surrounding the repair pad, you can scrape off some solder mask on the trace leading up to the edge of the repair pad and use solder to easily bridge from the repair pad down to the trace surface. If there is an epoxy excess you carve it out of the way with an xacto blade so you can solder bridge the replacement pad to the original trace, and also so the replacement capacitor tab can sit flush on the replacement pad.

 

[JDW]

I appreciate the detailed explanation. The content of your earlier posts makes a bit more sense now.

At this stage, it may be prudent for you to post some photos for us (on Flickr or a similar free hosting site). That way we can more clearly see what you are seeing and offer detailed advice. I personally would rather guide you based on what I see in a clear photo rather than based on what I read in text form. This is especially true since you are just starting out in the world of soldering.

 

[Mike Richardson]

I'll try and get some good macro shots of the board tomorrow of where it's broken off.

I need to get a LOT more capacitors. I've got a Performa 550 here with bad audio, and you know what that means...

 

[Mike Richardson]

http://www.silvernetworks.net/classic2/DSCF0069.JPG

Here's the broken solder pad area. The 3 nearby capacitors have already been replaced.

Please advise.

 

[Mike Richardson]

I attempted a repair; I put small bits of solder over the holes, then soldered a wire onto each of the small bits, and then put some hot glue over the whole thing to secure it. I soldered a capacitor to the wires. It did not work. I have removed all of it and now it is back to the way it was in the picture above.

 

[MdntTrain]

I attempted a repair; I put small bits of solder over the holes, then soldered a wire onto each of the small bits, and then put some hot glue over the whole thing to secure it. I soldered a capacitor to the wires. It did not work. I have removed all of it and now it is back to the way it was in the picture above.

No offense, Mike, but your soldering skills are making me cringe. lol. I think the board is repairable, but your skills and possibly tools and solder type need some evolution before that can happen.

If I were in this boat, I'd be using some fine wire strands (take apart a multistrand wire) to put down into those holes then solder them in there since I do see metal in each one.

~ J

 

[Maccess]

I think it's better to use the types of tools the cellphone repair guys use. These are the ones with minute jets of superheated air, instead of the the regular pencil types (unless it's an ultra pencil type.)

 

[Flash!]

The actual operation of touching the iron to the work and applying solder should only take seconds at most. Looks like you've got a heat problem Yeah the soldering could use a little work - but that only comes with experience (and starting with a dual-sided circuitboard doesn't make it any easier! [] ]'> )

For your remaining capacitor I'd just stick it upside down on that burnt patch of circuitboard with some glue, then I'd bend the legs 90 degrees and cut them short adding a couple of thin insulated wires and running them to the appropriate place on the circuit.

 

[da9000]

OMG, that photo looks like it came from Iraq! (which I may remind the uninitiated is widely considered one of the birthplaces of civilization, but sadly our lunatic leaders have bombed back to the stone age...)

Anyways, don't mean to poke old threads, but I can't believe NOBODY mentioned using FLUX! Hello!? Who does soldering without flux guys? You need to deoxidize the surfaces, no wonder Mr. Richardson's solder doesn't stick.

And one more thing: Tyleress is right about "replacing every component will not make something work". Other than the broken trace, or lifted pad, or damaged via [duct], what can happen which is a *major* bitch to fix is the following: a damaged part (call it A) causes a part downstream from it (call it B) to burn out. So you replace B, but before A, since you don't know it's the source of evil. You try the board and B gets burnt again, because A is still faulty, yet you DON'T know this has happened, since B is "brand new" as far as you know - you just soldered it! Then you continue and replace A. Try your board again and you still find your board not working. Basically you're screwed.

Of course one way to get around this is to replace all components at once, and then try your luck. But unfortunately you must be a God of perfection, because almost no human can achieve the same faultless run as a robotic parts machine.

And one last thing that I didn't see mentioned:

before you replace *all* the caps, see if any leaks exist (easily found by smell or if the solder around the caps isn't shiny, but very dull, or even yellow or green), and if they do you'd better clean them up with PCB cleaner or 99% pure alcohol, because they will corrode the board and traces and eventually no matter how much cap replacement you do, it will never work again!

Cheers and happy surgeries!