fixing a dead cap???

[philbrown23]

how would I desolder these capacitor legs to replace the cap?? i tried setting my iron on it but the solder didnt melt? I'm using a 60watt iron if that helps.

http://img442.imageshack.us/img442/9539/biostarvg2.th.jpg (http://img442.imageshack.us/my.php?image=biostarvg2.jpg)

[Sparky]

60W should be more than enough, I do those with a 25W iron all the time. Careful not to burn the board. If the tip is really dirty it can make it not work well however.

[Bobsama]

ROHS compatibiltity means that solder will need >1000 degrees to melt. That's most likely the problem. IF you have a torch and a cheap soldering iron, you can try to melt it by heating the cheap iron and applying the heat.

[tiro_uspsss]

ROHS compatibiltity means that solder will need >1000 degrees to melt. That's most likely the problem. IF you have a torch and a cheap soldering iron, you can try to melt it by heating the cheap iron and applying the heat.

:confused: links to proof please! :)

cant imagine how they'd do it in the factory then - @ that temp, when the molten solder hits the mobo, it'll 'melt/destroy' something for sure imo...

[philbrown23]

ok I managed to attach the new cap to the old cap legs, do you guys think this will be a problem in the future??

[tiro_uspsss]

also, philbrown23, note the circle is half black, half white - iirc this means the cap is positive/negative sensitive! - make sure u got it right way around ;) :up:

[celemine1Gig]

ROHS compatibiltity means that solder will need >1000 degrees to melt. That's most likely the problem. IF you have a torch and a cheap soldering iron, you can try to melt it by heating the cheap iron and applying the heat.


We are talking about soldering and not about welding. The soldering temps for ROHS, lead-free solder are around 220-250°C, depending on the particular type of solder.

As already said, the problem might be the soldering iron itself. Cheap old irons often have a big layer of oxidation on the tip that prevents the heat from travelling into the solder joint. 60W should be more than enough, though.
You could add some solder to the solder joint. That way you increase the heat that is transferred from the iron's tip to the solder pad, through the molten solder. But be careful not to burn any traces nearby that way.

And please don't just solder the replacement cap to the old legs. You increase the ESR (resitance) and the ESL (inductance) that way and this COULD have a negative influence on the circuit. If I remember correctly, theoretically you are building some sort of high-pass-filter with the extra resistance + inductance through the cap with the long "legs". You increase the resistance in the current path and the inductance to ground. As I said this could be negative, but I don't know how much of an influence it would be after all.


If you can, remove the old "legs" and cleanly solder in a new cap with the same or better characterisics than the old one. This way you can be sure to get the best possibe stability after the repair is done.

[Bobsama]

We are talking about soldering and not about welding. The soldering temps for ROHS, lead-free solder are around 220-250°C, depending on the particular type of solder.

As already said, the problem might be the soldering iron itself. Cheap old irons often have a big layer of oxidation on the tip that prevents the heat from travelling into the solder joint. 60W should be more than enough, though.
You could add some solder to the solder joint. That way you increase the heat that is transferred from the iron's tip to the solder pad, through the molten solder. But be careful not to burn any traces nearby that way.

And please don't just solder the replacement cap to the old legs. You increase the ESR (resitance) and the ESL (inductance) that way and this COULD have a negative influence on the circuit. If I remember correctly, theoretically you are building some sort of high-pass-filter with the extra resistance + inductance through the cap with the long "legs". You increase the resistance in the current path and the inductance to ground. As I said this could be negative, but I don't know how much of an influence it would be after all.


If you can, remove the old "legs" and cleanly solder in a new cap with the same or better characterisics than the old one. This way you can be sure to get the best possibe stability after the repair is done.

I don't keep up with those specs, but I do recall that the PrometheusCu build had an issue with an inability to desolder, that was remedied by a torch and a cheap iron.

[Jor3lBR]

ok I managed to attach the new cap to the old cap legs, do you guys think this will be a problem in the future??

That is no good mate, these things are very moody.

Are you sure you did it right, it cmes off so easy, just place the tip of the soldering iron on the leg of the cap from BEHIND the mobo, let it heat then PUSH the soldering iron into the leg till it comes 90% out then you only need pliers and a little bit of heat to take the rest out.

[3oh6]

I don't keep up with those specs, but I do recall that the PrometheusCu build had an issue with an inability to desolder, that was remedied by a torch and a cheap iron.
building circuit boards is what i do and those specs are bang on as is the advice for adding a bit of solder to help get the whole joint to flow. an ideal solutions would be a solder sucker but not everyone has those handy for through hole components.

to re-work lead free soldered components usually an iron temp of 750F~800F at the absolute most is all that is required compared to a steady 700F for standard or 'leaded' solder. advising people to use a torch when dealing with circuit boards is reckless and you should keep your ideas to yourself god forbid someone actually listen to your suggestions. we are here to help, not further damage hardware.

[Bobsama]

I'm sorry, I'm just throwing ideas out. What I was probably thinking of is the temperature from the torch. But you're the expert--I'll leave now as my knowledge is theoretical here. On a side note, do re-read what I wrote. I never said to use a torch directly on the board. Anyways--I do have experience replacing caps, but only on old boards. But yes--listen to the expert. I'm just a hobbyist.

[T_Flight]

I use a variable soldering station to control how much heat I need. I have a 30watt, and a 60 watt iron that I use depending on needs, but on siomething like this the 30 watt is plenty. In fact I woul;dn't even have it cut all the way up. Those little soldering stations are basically a variometer with a little rack for the iron.

You don't wanna keep heating things when soldering. Heat it up quick, get the part loose and remove the heat quickly. The hotter it gets and the longer you keep that heat there, the greater the potential to go outside of the circuit specs for temp/time.

Grab the old cap with some needlenose pliers, heat it up on the backside of the board on both pads and slide the cap out. It should slide right out quickly. If you heat it too hot, or too long you can scorch the solder making it very difficult to get out. That's a common mistake.

AFter it out, take some solder wick, and remove the old solder, then slide the new cap in place, trim the legs with a small pair of Dikes (Diagonal Side Cutters), or the needlenose cutters in the backside of the jaws, and heat the pad base and the leg at the same time for a few sexconds and apply solkder to the pad. The solder should melt itself. Don't touch the iron to the solder, let the base metal melt the solder or you'll get a "cold solder joint".

Make sure to observe proper polarity. ALL caps must observe proper polarity so be sure you note which way it came out, and put the new one in just like the old one came out. On some pads they have square and round pads to denote polarity.

A cap is basically a switching cycling storage battery...well, not really, but that's mostly what they are used for, and is the best way I can explain them. You wnat to use the correct microfarad rating and voltage rating unless you *really* understand the physics of volt modding. Never chnage the specs or vMod unless you thoroughly understand what the results will be after the mod is completed.

[RejZoR]

I replaced the cap on my X-Fi with the most regular solder tool, very old thingie that we had for ages at home.
If you're unsure how hot it is just avoid having prolonged exposures to the PCB and solder points on it and everything should be fine.
Just heat up existing solder, pop one cap contact at a time and blow at the PCB quickly after you remove each to cool it down faster.
Place new one in, add little solder on solder point and do the magic.

[Thrmionicshaman]

building circuit boards is what i do and those specs are bang on as is the advice for adding a bit of solder to help get the whole joint to flow. an ideal solutions would be a solder sucker but not everyone has those handy for through hole components.

to re-work lead free soldered components usually an iron temp of 750F~800F at the absolute most is all that is required compared to a steady 700F for standard or 'leaded' solder. advising people to use a torch when dealing with circuit boards is reckless and you should keep your ideas to yourself god forbid someone actually listen to your suggestions. we are here to help, not further damage hardware.

+1
I build/repair/[volt]mod guitar Amps:yepp: and I must say that is sound advice.
Also to anyone- desoldering braid is awesome-it changed my life and it can change yours too:rofl: Plus it's cheap and does the trick when the $10 solder-sucker might have recoil that messes up what you are working on.It's either that or a $250+ desoldering station.Gotta get me one:yepp:

[eligray]

torch worked wonders for me today removing a six-pin power plug from an old VGA card ;)

[eligray]

Plus it's cheap and does the trick when the $10 solder-sucker might have recoil that messes up what you are working on.

there are units without recoil? mine must've jumped a whole inch today when I was trying it out, before resorting to the torch :(

[Thrmionicshaman]

Graveyard parts RULE!

[eligray]

On caps where one of the metal rods starts to pull out, can it just be pushed back in or should it be discarded?

[CryptiK]

I'd chuck it and use a good cap. You need to know it's functioning 100% correctly.

[s0lid]

When i remove old caps i set my soldering irons thermostat to 410c, add little lead to both legs and heat up both legs 10-15s at same time then cap drops from mobo/graphic card :P
Tho cleaning the holes is not so nice :|

Have to use some special lead vacuum or drill the holes...