Bad Cap Replacement Help

[PCBONEZ]

Re: Bad Cap Replacement Help

As to the markings, which do you mean?
Some are standard and others vary from brand to brand.

[Clem16]

Re: Bad Cap Replacement Help

3.5LS = 3.5mm Lead Spacing

Normally 8mm diameter caps have a 3.5mm LS and 10mm caps have a 5mm LS but there are exceptions.

Oh! so this has nothing to do with the internals of the spacing of the plates inside the capacitor. Your talking about the Leads that come out of the capacitor and you soder to a board. DOH! I get it now .. that was defenitlly a homer simpson moment.

[Clem16]

Re: Bad Cap Replacement Help

As to the markings, which do you mean?
Some are standard and others vary from brand to brand.

Oh I am just wondering if there is some good general guides to understanding how to identify a capacitor.
Also what are the "important" markings that I should be looking for when I attempt to find a replacement.

(Simply trying to learn enought to be able to identify a bad capacitor, and go about finding a replacement without having to run to the forums for help with every single little thing every time. I have a stack of motherboards which I think have bad capacitors....)

[PCBONEZ]

Re: Bad Cap Replacement Help

In order to choose PROPER replacements you need to look up the ripple and ESR in data sheets.
[Which basically means an internet session for each project.]

Ripple needs to be the same or more.
ESR needs to be the same or less.
GP caps [General Purpose] won't have ESR listed so just use Ripple.

For low ESR caps if it is not a Japanese brand it is questionable.
If it is one of the following Japanese low ESR caps it is still a potential problem.
... Chemicon KZG and KZJ. [High failure rates and often fail without bloating.]
... Nichicon HM and HN in the bad date range.
... Any 85C caps where 105C should have been used.
[There are good brands outside of Asia but none make low ESR electrolytic caps.]
.

[TheLaw]

Re: Bad Cap Replacement Help

Information printed on capacitors:

Capacitance rating: This is the amount of electricity the capacitor is capable of holding. They have common values that are usually mutiples of 10, 22, 47, 56, 68, 82. So you might see 4700uF or 0.47uF. On electrolytics they are measured in micro-farads. (μF) Because the micro symbol is not readily available on a keyboard, people just use a "u" instead.

Voltage rating: This is how much voltage the capacitor can tolerate before it starts failing, or explodes. It is NOT how much voltage it is charged to at any given time. That is dictated by the circuit it is a part of. There are also standard values for this: 6.3, 10, 15, 20, 35, 50 and multiples.

Manufacturer: This is obviously who made it. There are a lot of brands of capacitors but it's pretty obvious. Alot of capacitor brands end in "con" (Nichicon, Rubycon, United Chemi-con, etc). But don't be fooled. Just because they end in "con" doesn't mean they are good by any means. Take Jackcon for an example.

Capacitor Series: This is typically a 2-4 letter string. Capacitor manufacturers make many different lines of capacitors for different uses/prices. In your case, HN and HM are the capacitor serieses. Other examples are KMG, MBZ, FM, VR etc. You'll be able to tell.

Date Code: This is when the capacitor was manufactuered. However, they do not physically print "March 4th, 2003" on the capacitor, but rather a combination of letters/numbers. They are usually NOT in the same place as the capacitance, voltage rating, brand etc. You must refer to the manufacturer's date code system to determine when it was manufactured. It is beneficial because faulty capacitors are manufacturerd from time to time, and a company might announce in what time period bad caps were produced.

Tolerance rating: Typically it printed next to the name of the series in parentheses. So HN (M) is an example. However, sometimes they are printed next to the temperature rating. Tolerance does not mean how much a capacitor can handle, but rather how close the actual capacitance of your capacitor is to the value printed on the sleeve. There are many values of tolerance, however, (M) is the most common. It represents +/- 20. (K) is about the only other one you will see on electrolytics, (+/-10%).

Temperature Rating: Generally speaking, it is how hot the capacitor's ambient temperature can be for it to function without significant deteriation. General purpose capacitors are frequently found at 85*C, while most higher end capacitors are rated for 105*C. There is also 125*C, 135*C, and 150*C. However, you have to make some tradeoffs when buying high temperature capacitors. The temperature is easy to find. It's usually on the opposite side of the capacitance rating, and voltage.

Thick Line Thing: The think line that runs down the side of the capacitor corresponds to one of the leads of the capacitor, and it means that it is a negative lead. So the side with the line is negative, and the side without, is positive. Don't put it is incorrectly. Failure to do so will typically cause a circuit to not work/work incorrectly, and can cause the capacitor to blow up if there is enough energy to do so.


Just the basic stuff. When you are replacing a capacitor though, the most important thing is to look at the datasheet. There are tons of capacitors rated at 2200uF 16V and 105*C. However, the ripple current rating and ESR rating can be VERY different. So never replace a capacitor purely by looking at the print on the sleeve of the capacitor.

[Clem16]

Re: Bad Cap Replacement Help

Information printed on capacitors:

Capacitance rating: This is the amount of electricity the capacitor is capable of holding. They have common values that are usually mutiples of 10, 22, 47, 56, 68, 82. So you might see 4700uF or 0.47uF. On electrolytics they are measured in micro-farads. (μF) Because the micro symbol is not readily available on a keyboard, people just use a "u" instead.

Voltage rating: This is how much voltage the capacitor can tolerate before it starts failing, or explodes. It is NOT how much voltage it is charged to at any given time. That is dictated by the circuit it is a part of. There are also standard values for this: 6.3, 10, 15, 20, 35, 50 and multiples.

Manufacturer: This is obviously who made it. There are a lot of brands of capacitors but it's pretty obvious. Alot of capacitor brands end in "con" (Nichicon, Rubycon, United Chemi-con, etc). But don't be fooled. Just because they end in "con" doesn't mean they are good by any means. Take Jackcon for an example.

Capacitor Series: This is typically a 2-4 letter string. Capacitor manufacturers make many different lines of capacitors for different uses/prices. In your case, HN and HM are the capacitor serieses. Other examples are KMG, MBZ, FM, VR etc. You'll be able to tell.

Date Code: This is when the capacitor was manufactuered. However, they do not physically print "March 4th, 2003" on the capacitor, but rather a combination of letters/numbers. They are usually NOT in the same place as the capacitance, voltage rating, brand etc. You must refer to the manufacturer's date code system to determine when it was manufactured. It is beneficial because faulty capacitors are manufacturerd from time to time, and a company might announce in what time period bad caps were produced.

Tolerance rating: Typically it printed next to the name of the series in parentheses. So HN (M) is an example. However, sometimes they are printed next to the temperature rating. Tolerance does not mean how much a capacitor can handle, but rather how close the actual capacitance of your capacitor is to the value printed on the sleeve. There are many values of tolerance, however, (M) is the most common. It represents +/- 20. (K) is about the only other one you will see on electrolytics, (+/-10%).

Temperature Rating: Generally speaking, it is how hot the capacitor's ambient temperature can be for it to function without significant deteriation. General purpose capacitors are frequently found at 85*C, while most higher end capacitors are rated for 105*C. There is also 125*C, 135*C, and 150*C. However, you have to make some tradeoffs when buying high temperature capacitors. The temperature is easy to find. It's usually on the opposite side of the capacitance rating, and voltage.

Thick Line Thing: The think line that runs down the side of the capacitor corresponds to one of the leads of the capacitor, and it means that it is a negative lead. So the side with the line is negative, and the side without, is positive. Don't put it is incorrectly. Failure to do so will typically cause a circuit to not work/work incorrectly, and can cause the capacitor to blow up if there is enough energy to do so.


Just the basic stuff. When you are replacing a capacitor though, the most important thing is to look at the datasheet. There are tons of capacitors rated at 2200uF 16V and 105*C. However, the ripple current rating and ESR rating can be VERY different. So never replace a capacitor purely by looking at the print on the sleeve of the capacitor.

Thank you very informative just the sort of information I was looking for. It's all simple stuff that most people who whork with electronics just know off heart and assume others do as well. Most of it I had a basic idea of but you clarified some key points. I have a bit before my order arrives so between now and when it gets here I have time to study up on everything. One small step at a time, as I assume just busting out the soldering iron and randomly poking away at the board would be a bad thing....

[PCBONEZ]

Re: Bad Cap Replacement Help

Thanks TheLaw. I was kind'a swamped yesterday afternoon as a couple of servers were staging a revolt against the establishment and I'm the establishment.
One correction though.
Standard/common Lytics voltages go 4, 6.3, 10, 16, 25, 35, 50, 63.
4 is kinda weird for Lytics but OST 4v Lytics have shown up in VRMs.

~~~
Back to the question:

Most of the low ESR caps used in PC equipment's are there as 'filters'.
What they do is take the 'noise' [Ripple and EMI are both kinds of noise] and short it to ground which 'cleans' the DC voltage.
[Caps are said to block DC and pass AC. Noise is basically non sine-wave [random] AC.]
-
The difference between Ripple and EMI is the source of it and the frequency.
- Ripple comes from 'switching' transistors [often MOSFETs] used in voltage regulators. ['Switching' just means they work by turning on-off very fast.]
SMPS power supplies are the major source of ripple but it also comes from the smaller POL regulators scattered all over the PCB. [POL = Point of Load, PCB = Printed Circuit Board.] POL regulators can be single chip regulators or almost as complex as a complete SMPS. The VRM [CPU voltage regulator 'module'] is basically a POL SMPS.
The frequency of ripple is usually in the range of 50-200 kHz which is why low ESR caps are rated for ESR and Ripple at 100kHz.
- EMI is primarily RF [radio frequency] noise that gets 'picked up' by way of the antenna effect any place you have conductors. Filter caps for this are usually small uF [10-220uF] and usually connected to places that have long runs of conductor [board traces] or that are connected to external wires that might act as an antenna such as VGA, USB, PS/2, fire wire, speakers, Serial/Parallel ports.

- So on to the point.

The ESR rating is basically the cap's 'resistance' to passing AC at 100kHz.
Since a low ESR cap's main job is to pass Ripple to ground a small 'resistance' to Ripple passing through the cap is desirable. - That said, the cap is often not the only part of a filter. Often inductors [and sometimes resistors] are used with cap to optimize the filtering at the expected Ripple frequency. If you replace a cap and lower the ESR too far you can 'de-tune' the filter such that it is less efficient at the specific Ripple frequency the circuit is expected to see. [They teach techs how filters work using uF at RF frequencies which is based on Xc and Xl. But at roughly 100kHz Xc and Xl cancel each other out and ESR is the only thing affecting the cap's impedance [and so the only thing affecting the filter's frequency response.]

The Ripple rating is in milliamps.
It tells you how -much- Ripple the cap can pass without overheating internally. It is the same idea as the watt rating of a resistor or the amps rating of a wire but it specific to the Ripple passing through the cap.

Hope that helps.
.

[TheLaw]

Re: Bad Cap Replacement Help

Thank you very informative just the sort of information I was looking for. It's all simple stuff that most people who whork with electronics just know off heart and assume others do as well. Most of it I had a basic idea of but you clarified some key points. I have a bit before my order arrives so between now and when it gets here I have time to study up on everything. One small step at a time, as I assume just busting out the soldering iron and randomly poking away at the board would be a bad thing....

Make sure you have a fine tip. Don't use a 0.5in chisel tip please. See if you have any spare PCI cards/motherboards/power supplies around in your parts bin etc. Try playing around on those first. I personally use solder wick to desolder. I think it works quite well. I do have a cheap desoldering iron, but it doesn't work too well on small joints. Thin solder works best, ~0.031" or less. I buy them in 1lb spools for around $25. Kester 44 63/37 is good stuff. But you can get a few ounces at Radio Shack for only a few bucks.

1.) Apply a bit of solder to the solder joint. This will effectively "loosen up" the old joint.

2.) Place the solder braid/wick on the joint.

3.) Place your soldering iron's tip on TOP of the solder wick. You will be able to see the braid "suck up" the solder form the joint.

Also make sure your iron is hot enough. On my iron, I turn the dial to about 4-5. I usually solder on about 3. (Weller WLC100 iron). 40W is usually recomended as a minimum, but I think you could still get away with about 30W alright.

For motherboards, you have to be careful where you are putting your tip. There are traces the width of a piece of 30AWG wire (sorry can't find a good analogy).

There's many different strategies. Not all people may agree with the solder wick approach. Just make sure you are heating the solder joint and not melting/shorting the traces around it.

[Clem16]

Re: Bad Cap Replacement Help

Hi, I need to get some solder wick if i want to do this "correctly", (Which I do).

My soldering iron is a Weller WP35. But as you can see by the pictures the tip has not been looked after very well. I should probally buy a replacement tip. Any suggestions for tiny work like this?

The solder I have I am not sure of the brand but its solid core. You can see by the pictures the size. Its fairly fine so I think the solder will be ok.

I just used this iron and solder to fix a flash drive that had the usb port coming loose from the board and it worked fine. Drive works beautifully now.

Any suggestions on where I can get some cheap solder wick? I have never used the stuff before.

I am a trained welder so soldering is quite easy for me. I just have not done as much of it as I have welding. I find when I am soldering becuase I have welded in the past I tend to apply to much heat becasue I am used to working with higher heats.

[Clem16]

Re: Bad Cap Replacement Help

Woops forgot to attach pictures.

[TheLaw]

Re: Bad Cap Replacement Help

Phew! At least you have a decent iron. I recommend Weller ST7 tips for small work. A chisel tip might be helpful with some of the bigger joints, but I wouldn't bother getting another.

And make sure to tin that tip frequently! Like after every couple of joints you solder! Solder wick? Seeing you live in Canada, try going to The Source (Radio Shack in the US). That's where I get mine from. You can also get it off Amazon, but it'll get costly. It's like $3. You'll think it's really expensive for how small the spool is, but it's worth it.

That solder is fairly thin, yes, but rosin core 63/37 makes soldering soooo much easier. You can probably get a bit of solder from The Source/your local electronics store for about $5. However, if you are confident with using solid core and know how to properly clean the pads etc, by all means. Just a suggestion.

[TheLaw]

Re: Bad Cap Replacement Help

There's a lot of techniques to desolder.

Some people prefer to apply some solder to the leads of the capacitor first, then to heat up both joints simultaneously (switching rapidly between the two), and then remove the capacitor.

After it has been removing, then you use the solder wick to suck up the solder.

You can also use a solder sucker. There are many ways. Refer to the guide on the Badcaps.net homepage for reference. That one does NOT use the solder wick method, and it might be a better choice...but it all really depends.

Sorry to be so unclear.

[Clem16]

Re: Bad Cap Replacement Help

Ok sounds like I will use the solder wick method. I plan on putting slight preasure on one side of the capacitor and simotaniouslly applying heat to one of the leads till it comes out of the hold. then Reversing my preasure and doing the other. Then I plan to clean the holes. This is going to be the hard part, since it looks as if i have to go on a shopping trip and get some solder wick :P

By cleaning the pads i assume you mean the little spot on the motherboard which has solder on it.

Why is it nessisary to clean all the old solder off of the motherboard before replacing the capacitor will not the new solder just mix with the old or will it cause problems if two solders mix?

[TheLaw]

Re: Bad Cap Replacement Help

Ok sounds like I will use the solder wick method. I plan on putting slight preasure on one side of the capacitor and simotaniouslly applying heat to one of the leads till it comes out of the hold. then Reversing my preasure and doing the other. Then I plan to clean the holes. This is going to be the hard part, since it looks as if i have to go on a shopping trip and get some solder wick :P

By cleaning the pads i assume you mean the little spot on the motherboard which has solder on it.

Why is it nessisary to clean all the old solder off of the motherboard before replacing the capacitor will not the new solder just mix with the old or will it cause problems if two solders mix?

Usually it's not terrible to mix solders. Some might advise against it, but it'll work.

The most important part is to get the hole clean. If you start forcing the cap in/out on a multilayer board like a motherboard, you'll mess something up.

I'd recommend removing both leads of the capacitor out at the same time if you can...to avoid stress on the pads etc.

Yes pads are the little circles with the holes in them where you apply solder to.

[PCBONEZ]

Re: Bad Cap Replacement Help

Mixing solders doesn't hurt anything.

In fact if you dealing with lead-free solder [as found on the board] and you don't have a hot-hot iron it's preferable to mix little leaded solder into the joint before you try removing any. Lead-free solder has just enough higher [as much as 20 °C higher] a melting point to be a serious pita otherwise. Sometimes it just refuses to flow at all.

63/37 or 60/40 are fine with 63/37 having a slight advantage of a little lower melting point.

I like rosin-core in .020-.022" [about 0.5mm] diameter unless it's a big joint.
The small diameter gets the solder flowing into the joint sooner which helps transfer heat into the joint.

If anyone gives you crap about RoHS show them your middle finger.
RoHS applies to manufacturing, not repair. [At least in the US.]
[That's my story and I'm sticking to it...]

Use fluxed wick. It works much better.
If you can't find it then flux the wick before you use it.
.

[Clem16]

Re: Bad Cap Replacement Help

If anyone gives you crap about RoHS show them your middle finger.
RoHS applies to manufacturing, not repair. [At least in the US.]
[That's my story and I'm sticking to it...]

Use fluxed wick. It works much better.
If you can't find it then flux the wick before you use it.
.

! Considering the morons I am surounded by daily I would be suprised if anyone even here knew what RoHS is. I do simply because when I get a new piece of hardware I pour over its tech specs and have run across the term before. But if anyone here makes a fuss I have a pair of CSA Aproved steel toed work boots a proctologist will become very aquainted with removing from the offender...

What is the advantages of using a fluxed wick? Does it coat the surface of the melted lead and keep it from (I want to say oxidizing but not sure if that term is correct) while it is wicked up?. (I have never used solder wicks before)

[PCBONEZ]

Re: Bad Cap Replacement Help

Solder flows into the wick better when it's fluxed.
I'm not 100% sure why, but it does.
.
It helps if you loosen up the braid [a little] after you pull it off the spool too.
Pulling it off tightens the braid which reduces the air gaps that the capillary action draws the solder into.
Different wicks work differently with varying degrees of 'braid looseness' too.
That's something you'll have to experiment with for whatever braid you get.
The easiest way to loosen it is to grasp two points about an inch apart and push the two grasp points towards each other [like with releasing a Chinese finger trap].
-
Braids are color coded by size. [Or rather the spool is.]
You might want to get one each of blue and green to see what works best for you.
I keep both handy because sometimes the green works better and other times the blue does.
.

[PCBONEZ]

Re: Bad Cap Replacement Help

Apparently there are two blue sizes and two green sizes.
These are what I get.
0.08" [2.03mm] Green
0.10" [2.54mm] Blue

[Clem16]

Re: Bad Cap Replacement Help

Well I recieved the Capacitors I ordered from Mouser. I got 10 560uF 6.3v HN(M) by nichicon. I also got 2 2200uF 10v HN(M) by nichicon.

These caps are identicle to the ones I have on the board, should I worry that they might be defective as well? or are the nichicon caps dependable thesedays?

I find it quite funny that 12 little capacitors needed a foot long box with several feet of buble rap to ship in. Anywyas. Let me know any comments you guys have. thx.

~Clem

[PCBONEZ]

Re: Bad Cap Replacement Help

They are fine.
Only the ones with 2001-2004 date codes are bad.
.