How do you remove smd electrolytic caps?

[Spork Schivago]

Re: How do you remove smd electrolytic caps?

Remember, you can change them with some radial caps, just solder the legs to the pads, they are cheaper and easier to find, and don't forget to look for similar esr and capacitance

You mean like through-hole? Just bend the legs and solder them on? Okay. That'll open up the doors a bit, but I'm a little worried about spacing. A bunch of these will have part of a heat sink right in the way...the current ones aren't very tall at all, but the radial ones might be a lot taller.

[Spork Schivago]

Re: How do you remove smd electrolytic caps?

I would just look at how its used in the circuit, In a switching supply secondary for example when one side of the cap is ground the ther side should have very little ripple, if you check it and you see a couple volts of ripple on it, its a good chance its going bad, If it was in an audio or video amp for example and used to couple the signal from one section to another, you should have close to the same waveform on both sides, if the input side had 1 volt p/p and output side had 1/2 volt again its a good chance its not doing its job.
I've seen the output of regulator ic's with so much noise they start to radiate into other parts of the circuit but ther dc voltage was still acceptable and when checked with a meter they looked fine.
I find the scope a real time saver, If you use it all the time you get familiar with what you should see, it sure beats removing parts to check them, if what I see does'nt look right,then I would pull the cap and check it, or if its just a small one I would just replace it with a new one if I had one.

Thanks for the info. I want to get one of those isolation transformers, then I'll use it to check everything from now on, to get an idea of what things are supposed to look like, so I might know when something's wrong, in the future, you know?

[Spork Schivago]

Re: How do you remove smd electrolytic caps?

Shit. So, I replaced that SMT cap with a 35V 100uF through hole cap that I bought from RadioShack when they were going out of business. Still clicks. I was testing some stuff and was showing my wife how I originally thought it was the board that says Converter (I thought it was an inverter). I said it'd suck if we replaced the entire motherboard and that's not the problem. So I start unplugging all the unnecessary cables and decide this time to unplug the hard drive cable, even though the hard drive isn't physically installed. Sure enough, starts right up.

There's something physically wrong with the hard drive cable I think. I plug just the hard drive cable into the optical power header, and it clicks. I unplug it, it stops. Maybe there's a short somewheres, I gotta do some more digging now, but I think that cap might have been perfectly fine.

[petehall347]

Re: How do you remove smd electrolytic caps?

seems you are getting somewhere

[Spork Schivago]

Re: How do you remove smd electrolytic caps?

Yeah, but I think I'm going to move this over to the computer sub-forum now. Something's wrong somewheres. I figured maybe the power connector had a short, right? Four wires, a red, two blacks and a yellow. I check the continuity, only the two blacks share continuity, so no short. Just plugging that wire into the header causes the ticking noise and no boot, like it's bad somehow, but it seems to test okay. I don't get it.

[petehall347]

Re: How do you remove smd electrolytic caps?

maybe the insulation is bad and only shorts if in certain position . or the socket is bad or around it .. best way is change cable and see what happens .
try meter on meg-ohms when looking for shorts and you might find leakage if your meter is up to it .
another thought is it could be the way the grounds are connected at the socket . if they run separate grounds it is a good clue especially if they join together in the cable .

[diif]

Re: How do you remove smd electrolytic caps?

Yeah, but I think I'm going to move this over to the computer sub-forum now. Something's wrong somewheres. I figured maybe the power connector had a short, right? Four wires, a red, two blacks and a yellow. I check the continuity, only the two blacks share continuity, so no short. Just plugging that wire into the header causes the ticking noise and no boot, like it's bad somehow, but it seems to test okay. I don't get it.

Faulty hard drive ? Have you pulled it and tested in another PC ?
Have you stuck a spare hard drive in and seen if it boots ?
Photos as always will help.

[Spork Schivago]

Re: How do you remove smd electrolytic caps?

maybe the insulation is bad and only shorts if in certain position . or the socket is bad or around it .. best way is change cable and see what happens .
try meter on meg-ohms when looking for shorts and you might find leakage if your meter is up to it .
another thought is it could be the way the grounds are connected at the socket . if they run separate grounds it is a good clue especially if they join together in the cable .

Yeah, I've ordered a replacement cable. Right now, I'm thinking maybe it's something in the socket that connects to the hard drive.

[Spork Schivago]

Re: How do you remove smd electrolytic caps?

Faulty hard drive ? Have you pulled it and tested in another PC ?
Have you stuck a spare hard drive in and seen if it boots ?
Photos as always will help.

With no hard drive attached, just the cable, it won't physically start, like it's shorting out or something. When I remove the cable, it starts right up. I haven't tested the hard drive, I just completely removed it.

Here's a link to a picture of what the cable looks like. With just the four pin header plugged in (the power connector, not the data connector), the PC doesn't start. No hard drive plugged into the cable, just that four pin plug, that's all. I checked all the insulation on the four wires there, they're all good. I'm thinking maybe it's something inside that connector that connects to the hard drive. I can't open it up to tell, not without ruining it at least.

http://cdn1.bigcommerce.com/server42...0.1280.JPG?c=2

[Spork Schivago]

Re: How do you remove smd electrolytic caps?

PC is fixed. I feel kinda dumb for not removing that power cable originally. I thought just having the hard drive unplugged was enough. Never thought there could be some sort of short inside the connector, but that's what it was, and it's fixed now.

I did replace that one capacitor with a through-hole one (just bent the leads and shortened them a bit). I'm hoping that doesn't cause too many issues, being just a regular bought-at-radio-shack cap. It was rated for 105 degrees C though, so I'm thinking it'll be okay.

Thanks for all the help! It was definitely a learning experience!

[petehall347]

Re: How do you remove smd electrolytic caps?

that is something that isnt really suspect .. well done finding it .

[Spork Schivago]

Re: How do you remove smd electrolytic caps?

Yeah, I guess that's what makes it a learning experience. When it comes to testing, making sure you're thorough and even check the stuff that doesn't normally fail. Man, the symptoms really made me think bad board. I've seen dead hard drives before that had similar symptoms (although I've only seen it once or twice). Never where a cable like this caused these symptoms though. I wonder how many laptop motherboards I've replaced that had a shorted out SATA connector...

[petehall347]

Re: How do you remove smd electrolytic caps?

hope you cut the old lead in half ..

[diif]

Re: How do you remove smd electrolytic caps?

One of the first things I was taught when diagnosing/fixing dead stuff. Remove everything apart from known working memory and CPU. If it then boots, add stuff until it stops.

[Spork Schivago]

Re: How do you remove smd electrolytic caps?

One of the first things I was taught when diagnosing/fixing dead stuff. Remove everything apart from known working memory and CPU. If it then boots, add stuff until it stops.

Yeah, same here. I was just being lazy I guess. I remember thinking, eh, it's just a cable, that'll be fine. It's kinda like finding a bad CPU fan that prevents the system from starting or something like that! Normally, you don't unplug the CPU fan when testing. I should have just unplugged it, rather than removing the hard drive.

At least she's up and running now and didn't require a new board.

[Agent24]

Re: How do you remove smd electrolytic caps?

I saw a laptop power adapter with a shorted cable. Never thought that would happen, either.

[Spork Schivago]

Re: How do you remove smd electrolytic caps?

I saw a laptop power adapter with a shorted cable. Never thought that would happen, either.

Do you mean the transformer? The part that plugs into the AC outlet and then the other end plugs into the laptop? I've ran across a few of those that were dead. I tried taking one apart once, in an attempt to repair it, but it wasn't meant to be taken apart. I broke the bezel (it was glued or something) and then inside, the entire thing was filled solid with some sort of epoxy. A giant rectangular white brick. It felt rubbery like but I wasn't going to try to remove all that just to repair the transformer.

Not sure what happened in any of them. Maybe bad caps? I dunno. I thought there might be a fuse in them or something that might be blown. I've found some that have voltages but they jump around like crazy, and then others that are 100% dead.

[Agent24]

Re: How do you remove smd electrolytic caps?

Yes.

The low-voltage output side cable to the laptop was shorted, probably at the plug.

They're just single-rail SMPS like any other, along with no schematics, of course. The cheap generic ones are simpler and easier to fix, though...

[petehall347]

Re: How do you remove smd electrolytic caps?

i always find the wire on them to be broke at the dc plug or where the wire enters the brick .. have fixed plenty of them ... folk think they can drag them around .

[Spork Schivago]

Re: How do you remove smd electrolytic caps?

i always find the wire on them to be broke at the dc plug or where the wire enters the brick .. have fixed plenty of them ... folk think they can drag them around .

I found that a lot, where it enters the brick. How do you open the transformer without damaging it? Do they normally open pretty easy for you? I only tried that one, which of course, I ruined in trying to open it. I don't think the company that made it wanted it opened or repaired.