Why desolder the old?

[Grefven]

Why do I need to completely desolder and clean the hole in the MB when I try to recap my board (Asus P4PA)?

The simplest way must be to simply "destroy" the old capacitors, keeping its leads on the motherboard and then solder the new capacitor on these leads?

Tell me why/why not to do this?

I have tried on another board (not an MB) to do this, and I found that it was possible to "pull" the old capacitor straight up and the leads would then slip out of the capacitor and left there (somewhat trimmed) to accomodate the new capacitor.

Using this technique I would not need to have an iron at 450 degrees, and save a LOT of time and anxciety of damaging the board in the desoldering process.

Cheers from Sweden and a Dude who's preparing for his first cap-job.

/ Tomas

[arneson]

Re: Why desolder the old?

Heres my analogy, I blow a tire and I'm lazy, so I put the donut on the car and and leave it like that.
It still goes but it looks crappy and it's not safe.

[kc8adu]

Re: Why desolder the old?

1
it looks crappy
2
stray inductance from the long leads.
3
it looks like shit.
spend a few bucks and get proper tools that will allow you to do it right.
they can pay for themselves fast if you do a bunch of boards over the years.
you might even turn a profit if others around you need such work done.

[willawake]

Re: Why desolder the old?

its not that difficult anyway as long as you follow the guidelines, it just looks difficult and dangerous.

most important
- a hot enough soldering iron
- practice first
- dont work when you are tired or angry

i remember one of our members asked the same question a while back. but in fact he went on to recap many motherboards properly and did impressive work.

[Topcat]

Re: Why desolder the old?

I'm just going to pretend I never saw this thread....

[willawake]

Re: Why desolder the old?

hey now, todays are tomorrows recappers

[Topcat]

Re: Why desolder the old?

hey now, todays are tomorrows recappers

Actually, off the record.... I did do that once.... I had a server go down (VP6 with bad caps), and I didn't have time to remove the board and do it right (that server being down would have left about 20 websites down too), so while I waited for a replacement board, I pulled the couple bad caps off the board and soldered some used ones I cannibalized off another board onto the leads sticking up, soldering them with the board and hardware still in the case... It actually held for about a week, until the new board arrived. I swapped out the boards during off-peak time, and then recapped it the right way. As an emergency fix, it worked, but I certainly wouldn't recommend it.

[dood]

Re: Why desolder the old?

i remember one of our members asked the same question a while back. but in fact he went on to recap many motherboards properly and did impressive work.

Well, don't want to toot my own horn.... https://www.badcaps.net/forum/showthread.php?t=1150

[gonzo0815]

Re: Why desolder the old?

In motherboards, the leads of caps are very short. If you destroy the cap, the remaining leads are a aluminium alloy, wich is not likely to solder without some good ultra sonic soldering iron. If you manage, to glue a new cap in there, there are very bad contact at the solder joint and very long leads. Those long leads add more reesistance and inductive reactance, wich in the end my slow down the transient response, increase voltage drop, cause ringing on the line and may cause cpu errors or vrm controler errors and generall unstable system behaivior. If you move the system, it is more likely to loose a cap, wich in the end gives more trouble than doing it once right.
As long as you can afford a high wattage iron with a standard chisel tip, it isn`t that hard to do it right.

[starfury1]

Re: Why desolder the old?

2nd all of the above.

It really becomes a self defeating exercise to not do it right.

gonzo0815 has more or less summed up all the technical reasons as to WHY

Grab your self a decent set of tools to do the job and practice on stuffed or old MB etc
its something you have to learn for your self like ridding a bike

There is nothing like having the right tool for the job too...so if you don't want to spend too much money get a china made knock off 701 desolder station.
(not that the china knock off is the best buy, but costs about 5 times less then a real quality unit Pace Hakko etc)

You will still have to take some time to learn how to use it thought anyway

Lastly doing it that way is not going to win you any friends

If you start recapping other peoples MB that way ...

You will only gain a bad reputation when their computers stop working go flaky and guess who they are going to call first
(and probably not want to pay you),
then possibly second and then never again.

Do it once
Do it Right

learn the procedure

Now where was that post about sticking down popped caps with sticky tape again

[yanz]

Re: Why desolder the old?

i agree that we should do it the right way from the very beginning. still, i will always suggest for the new recapper to do it step by step. it's important to gather confidence for the project we do by seeing a progress. i usually bring back the mobo to full stable again after recapping caps on input and output vrm at first work. after knowing that my work is success (computer boot/post/memtest) than i recap all other places like memory area, agp, pci, near cmos etc and call it a day. i love perfect result.

I have tried on another board (not an MB) to do this, and I found that it was possible to "pull" the old capacitor straight up and the leads would then slip out of the capacitor and left there (somewhat trimmed) to accomodate the new capacitor.

Using this technique I would not need to have an iron at 450 degrees, and save a LOT of time and anxciety of damaging the board in the desoldering process.

i have no doubt this will 90% work. i once read overclockers.com's article abut this ghetto recapping. if you will recap it only one time in your life than go ahead. but if you'll recap more boards, it's important for yourself to do it right and build your skill with the right skill.

once u used to do it the wrong way, its hard to you to move to the bright side

[Fizzycapola]

Re: Why desolder the old?

I broke off some capacitors on my recap. I only did it because I thought I couldn't
remove them using the iron and tip and had been informed this was an ok technique
on another website - this proved to be false imo - the remaining leads I found much
harder to remove and I was very worried about damaging the rings also - for hours
I pondered giving up because of this mistake. My iron was only 40 watt and the
tip was huge and not melting the solder - particularly around the back of the board
where the VRM is located - there was just too much solder sucking the heat away before
it could get hot enough to melt. Eventually I was able to remove the
capacitors by a combination of heating directly the metal rings both at the same time
and edging the lead one at a time. I remember moving the leads up and down, not just
downward, when desoldering, up and down motion and finishing in pulling it out a bit
seemed to leave the cleanest hole.

I believe the simplest and most time saving technique would be heating both rings
at once sliding out the failed cap and sliding the new one in (maybe pulling the leads
through with long nose pliers - I don't recommend pushing the cap through as like
I found I'd bend the leads out of alignment and eventually the lead would become
twisted and stopped sliding in - in the final picture of my recap you can see some
of the caps are a few degree's out of alignment where I'd used this poor technique -
the finished result doesn't look nearly as good as the pro's here), then trim the leads
as small as possible and apply a small ammount of solder at the ring to ensure a
good finish being careful that the solder doesn't bead or make a bad join.

This to me seemed both the quickest and least technical technique. I do own
flux and desoldering tools but I think you need a higher proficiency to use them well,
just sliding out the caps and sliding in the new caps is the fastest technique surely,
unless of course you don't want to remove the motherboard when recapping - but
this only takes under 1 little minute and is just extreme deplorable laziness.

[willawake]

Re: Why desolder the old?

Technique is a personal thing and also depends on tools. personally i work one leg out at a time, i have found this to be best, sometimes one leg is more difficult than the other. Doing it this way though, care has to be taken not scratch a trace on the front of the board with one lead which comes out first.

If i have some difficulty like if the cap must come out vertical for instance if there is no room to wiggle it then i grab the cap with a pair of fat pliers. care must be taken with those to put only similar stress on the board as if fingers were used to remove the cap.

Pushing a new cap through existing solder might stress the internals of a cap not to mention the lead port. you want the new cap to be heated for a minimum duration. i think it will be longer that way.

also the existing solder is probably not going to make a very nice and strong connection so additional solder will have to be added. having two different solders may not be the best idea, considering that one may be lead free and one not.

[gonzo0815]

Re: Why desolder the old?

having two different solders may not be the best idea, considering that one may be lead free and one not.

Hm why not? a little lead can only help there IMHO

[willawake]

Re: Why desolder the old?

yeah i am not sure about that part of my post

[grand_amatic]

Re: Why desolder the old?

Well if not desoldering the old one is a problem...i have a question along those lines....why do I have to clean out the solder in the hole. Why cant I just heat up the solder pull the capasitor out and reheat the solder and put in the new capasitor..or does it not work like that.. You'll have to excuse my noobness.. i know you just talked about it but if the solder is hot it should just slide through causing no stress right?

[Topcat]

Re: Why desolder the old?

You're partly right there. I reflow the solder and pull the old cap out. I then clean the hole for the new cap. Without clearing or atleast reflowing the solder, you'll destroy the board before heating the hole up enough, holding the board, iron and the cap steady, and shoving a new cap in. No way around clearing the holes.

[gonzo0815]

Re: Why desolder the old?

I am usually generouse with new solder when recapping. Sometimes i use some SnAg leadfree, but even then i usually ad some 0,5mm leaded solder to. Especially for desoldering i usually ad some of the 0,5mm leaded solder, to allow easy melting of the solder. On most boards i can`t get the old solder to melt untill i add some fresh ones with new flux.

[grand_amatic]

Re: Why desolder the old?

I have a feeling im going to suck A$$. But i have an old board that IM going to practice on first....you have no idea how thankful I am that I found this site because I was blind going in and now I have some light on the subject. Thanks alot guys!

[willawake]

Re: Why desolder the old?

I have a feeling im going to suck A$$

you will if your soldering iron is not hot enough
otherwise you will do just fine