Thinking of doing my first recap

[toddstidham1]

Hey everyone. I guess like everyone else I ended up here after finding blown caps on a computer and figured they can be replaced. I was actually hoping I could find someone local to the Philadelphia area to do it for me. I've done some minor soldering before, but never a multi-layer pcb. Anyway, I've read all of the faqs and other posts but I guess I just need some confirmation before I begin. I have an older IBM P4 Desktop (1.8ghz) that I bought for 99 bucks for a friend that just needs a cheap computer (to replace their still functioning P166 Packard Bell on Win95). I can return this one and get another, but it'll cost me $30 just to mail it back and I'll get another one that'll probably have caps ready to fail. So I figured if I'm going to be out money, I may as well have a good running computer as the end result. This thing locks on post most of the time, occasionally locks after post or during CD Boot. I counted 19 bulged and leaking caps and another 6 that are just bulged, most are YEC but the uF is anywhere from 1500 down to lower then 1000 (some tiny ones).
So to the question, I have a 35w radio shack stick (which I've read may take too long to melt the solder) and an older weller 100/130 watt gun, not sure about the solder I have but looks like about .8 mm, I can get proper solder though. I don't have a sucker or wick but do have some SS sewing needles. What do you guys think? Should I attempt this or just take my chances with the replacement computer? Will the 100w gun be too much heat?

[stevo1210]

Re: Thinking of doing my first recap

100W is a bit too much heat. You need something that will produce from 350 - 450 degrees celcius of heat. I think the 35W radio shack stick would be better for the recap job.... but may pose a problem in melting solder maybe.
I use a 60W weller and it's perfect for recap jobs.
I think it would be better if you recap this PC because the replacment PC will probably have a bunch of bad caps too if they are both going to be the same model etc.

[starfury1]

Re: Thinking of doing my first recap

I suppose it depends on how skilled you are but yeah the 100W is a bit large.

It does take a far amount of heat to get the caps out and yeah most definitely you will have to use the needle to clear the holes.

The trick is lots of heat work fast and above all don't cook the PCB
make sure the tip is clean and add just a smidgen of solder to it to get good heat transfer.

one thing that was mention on these forums and its a point to bear in mind, you may find the positive + connection harder to get up to temp, this is as stated probably due to the power plain being closer to the top (component side) of the PCB so it acts more like a heat sink sucking the heat away from the joint, so it will require a bit more heat...you soon know when you try.

If you can, find some junk MB pcbs to practice on.... would be a very good idea...once you have perfect your skills then go for a real MB

you may find that the 100W with practice and perfecting your skill wont be to much of an issue, others here use an 60 W~ 80 watt iron for the removal side of this. (but being a gun type may be a pain)

You will mostly probably have to "Walk" the capacitors out
what this involves is heating one side then the other while pushing the cap from one side to the other while the solder has melted.

You will find most probably that the RS iron doesn't have a great heat dumping capacity and takes longer time to recover, get back up to temp

you will probably have no problem re soldering new caps in with it but may have to give it a little time between each soldering joint made.
it should only take about 2~3 seconds per joint to make a good solder joint
(provided the iron is up to the task)

Again clean, tip smidgen of solder and apply solder to the joint at the same time, (you never carry solder to a joint)

Normally soldering iron on pad and leg one side then put solder on pad leg other side, this should ensure surfaces are hot enough and a good solder joint will be made (see FAQ on flux removal or some threads here)


Its far better to do a recap I think, since the PCB is still working then buy another possible bunch of trouble.

What you need to do is learn the skill with practice first, its not that hard.

you have taken the first step by at least taking the time to read the FAQ's

Good luck

HTH cheers

[toddstidham1]

Re: Thinking of doing my first recap

Thanks for all the tips. Yea I have an old PIII 433 mobo here that is also flaky...runs but crashes alot, though the caps don't look blown, guess they could still be bad. Anyway, it's not worth saving so would make a great practice board. I'll definitely play around on that one first. Again, thanks for the encouragement. I guess I'll plan on ordering up a bunch of new caps and give this a go.

-Todd

[starfury1]

Re: Thinking of doing my first recap

caps can fail without any showing physical signs

Just make sure you buy the right caps for the job , Low ESR quality Brand for VRM (they are usally the ones around the CPU) and PSU output

search around the posts you see whats best for your MB

Cheers and welcome

practice in this game does make perfect

There are a few here who started were you are and have become very good recappers and quite knowledgeable on the subject...

[severach]

Re: Thinking of doing my first recap

Whether or not 100W is too much heat depends on how good you are at soldering or how good you can get with some practice. I have yet to find an iron as good as the Weller 8200 100/140 running at 140W. It's not regulated, not ESD safe, heavy as a brick, and has a really fat tip that pits quickly, but it's in my price range and it lets me produce good quality rework at a good speed on SAC305 soldered boards. I started with the Weller and wondered what all the fuss was about because the new solder wasn't that much harder than the old solder. I didn't know how much the Weller was doing for me until I bought supposedly better irons that made the work much slower and the quality much worse. Neither was improving with practice. It didn't take much practice to get to where I can solder with the 8200 almost as good as OEM rework which is pretty good since noone else here would be caught dead with such a crude tool near a motherboard.

The current heated 8200 so outperforms my Weller Thermaboost 30/130 and Hakko 936 that I've decided that any iron that uses a radiant heater no matter what the wattage or thermal recovery claims is useless for SAC305 work. Radiant heaters only regulate temperature well when heating the room not when you are trying to solder to some unseen copper adversary which is why the regulated ones need to be set to unreasonably high temps. A current heated iron delivers less watts to the room and more watts to the tip more quickly. This means you should consider your 100W iron to provide more than 3 times the heat and because it's unregulated, more than 3 times the danger than your 35W iron. If $100 radiant heated solder stations were all they are cracked up to be there wouldn't be $1000 + current heated solder stations waiting for buyers get tired of the cheesy ones.

The Weller is a wild machine and you will do some bad work like I did until you learn what not to do. Other guides are written to help you better use a soldering iron with lousy heat and a good tip which doesn't include your Rat Shack iron which has lousy heat and a lousy tip. My guide is written for an iron with good heat and a lousy tip. You might find as I have that lousy heat is a much harder problem to overcome than a lousy tip.

The Weller 8200 tip runs at a much higher temperature than radiant heat soldering irons so they corrode much more quickly. Dirty tips require too much pressure which bends and breaks the weak copper tip, puts scratches in the board, and fast moving irons burn lots of fingers. The tin plated tips clean easily so clean often. Clean tips heat with a light touch and a light touch makes for good precision. New tips are $2.99 a pair at Menards. The better you get the less you'll break. Keep extras and the wrench in your cap box. Loose screw terminals will make the Weller heat as poorly as other irons.

The high temperature and unlimited heat capacity of the Weller 8200 turns everything into a miniature soldering iron so some things should not be heated by direct contact. So long as the cap leads are exposed and immersed in solder only heat the leads. The contact area determines how much heat goes in and it is easy to control contact area with the leads. The wires will distribute the heat through the solder to the board internals. With some practice you can heat so accurately that you can heat the both leads of a narrow lead cap at the same time rocking back and forth to cut heat where there's too much and boost heat where there's too little. Move the cap leads only to determine which side needs more heat. Once both leads have just enough heat to move, goose them with a bit more heat to ensure the cap comes out on the first pull, all this in about 8 seconds without damaging the board by touching it. This makes short work removing the 1800uf caps on the GX270 boards.

When leads are not showing heat the solder pools from the center letting conduction heat the traces and the far side. Cap leads in solder get rid of heat easily but traces can't. Touching the traces directly will burn the glue quickly and the fat tip ensures you heat a wide swath of traces and burn lots of substrate. The solder will distribute the heat without burning anything.

I extract and insert caps and other two legged beasties with the rocking motion and I haven't lost any copper liners yet probably because the high heat keeps me from pushing too hard to figure out if the iron is working or goofing off. Clip and tin leads on new caps before insertion.

Solder in the hole makes the insertion easier so don't remove it. It gives you something to heat that can't be damaged, the hole doesn't need to be refilled, and with practice you can touch each solder pool the right amount to keep it just above the liquid temperature allowing each lead to slide through without difficulty. Once the tinned lead immersed in solder is exposed you heat that to increase your distance from the board to minimize the possibility of damage.

Sometimes the new joint is short of solder. Again heat the lead letting the heat and new solder flow on it's own.

For the short time I tried the Hakko 936 cap wiggling didn't work well for insertion so I had to clear holes with stainless steel pins. Pins come 250 to a box making them cheap enough to discard when bent. I found the smaller pin size was too weak to pierce and too small to let the leads through. I quit using the Hakko because I was burning too much substrate and the need for pins disappeared too.

I can't find any reference to a Weller 100/130 so I'll assume you have one like mine. Don't discount the Weller just because good sense says it is the wrong tool. Nothing less will do when soldering the GX270 heat sink. Every iron must heat and maintain the solder to the minimum temperature and the Weller is the fastest one I can find which allows me to minimize board contact. Your skill at manual regulation is what determines whether you do work comparable to regulated current heated solder stations or leave a wake of destruction. Get some solder skillz from pulling caps from discard boards and you might learn to like the Weller for SAC305 rework. A current heated ESD safe regulated iron would be superb but the price too high when a little know how gets results almost as good from something you might already own.

The Thermaboost is a good iron for tin/lead work in power supplies. The 130W setting is handy to melt the big leads on the large caps. The Hakko is pretty but so far the only use I can find for it is to make me look good.

[toddstidham1]

Re: Thinking of doing my first recap

Well, I got the 6 1500 uF caps out of my practice board. It went very smooth and easy. I went and bought a 45watt Radio Shack desolder iron with the vac bulb on it. I wasn't so good with the bulb itself but the iron worked great. 3-4 seconds of heat on each cap leg and they were out and everything looks clean. The practice boards caps all blew out the bottom. I'll solder some new caps in and see if it still boots (it did before I started, just gave lots of memory errors or windows would crash while booting). Anyway, the desolder irons hollow tip worked great. I could place it over the cap pin just above the board. As the pin moved down and out of the tip i angled the iron up so that just the outside edge was touching the solder pad and that kept enough heat to release the pin from the board. I was pretty surprised how easy it went considering everything I read about how difficult removing the bad caps would be.

Of course doing the IBM board will be alot harder since it looks like I have about 25 caps that need to be replaced and another 5-6 that don't look bad, but are the same size/markings of ones that did go bad so they should be replaced as well.

Like I said the Weller gun that I have is pretty old (i'm thinking 60's or 70's) and I'm pretty sure it was a 100/130 watt unit. It came from my brother's wife's grandfather and was very lightly used (the spare tips are still brand new). Almost like he bought it to fix one thing and then never used it again.

Thanks for all the tips/advice guys. I'll post my results from the practice board when I finish it.

[shadow99]

Re: Thinking of doing my first recap

If you dont like to, dont wanna bother, or cant remove the caps from the pc board properly and dont care what the finished board looks like then cut the old ones off from the top. This leaves the original soldered connection intact and eliminates the risk of board damage.

Use sidecutters to chop the cap off about 2/3 down which leaves the rubber seal and a decent length of lead. Slide the rubber seal and remaining piece of can from the leads, tin the leads sticking out of the board and on your new cap and solder the new cap to the leads. Making sure polarity is correct of course.

I used that method on 2 of my own boards in the past year and both are working fine, being used every day.

[linuxguru]

Re: Thinking of doing my first recap

Replace every YEC, regardless of visible condition. They're guaranteed to fail, even when not in use.

[kc8adu]

Re: Thinking of doing my first recap

Replace every YEC, regardless of visible condition. They're guaranteed to fail, even when not in use.

i still remember the stink when desoldering 50+ yec caps in the then 1 year old uniden sat recievers.
they have not improved.
just recapped 40 of the ibm 2200 thin clients.full of yec.
even the ones not bulging were open.

[bgavin]

Re: Thinking of doing my first recap

I bought the Hakko 936, and have been recapping like crazy with it. All my jobs work fine when completed. I use the small chisel tip, and 450C. I clean the holes using the pin method. Works great for me.

[Leung Kai-yan]

Re: Thinking of doing my first recap

Dear Friend,
A good 40 watts iron is OK. The tip of the hot iron touches only the holes but not any part of the printed circuit. It is not a must to remove all the old solder in the holes. For the tools and instruments, please see the photos.

[Leung Kai-yan]

Re: Thinking of doing my first recap

Dear Friend,
I have 3 motherboards of this model. The capacitors of all of them have been successfully replaced. These are two of them (after replacement).

[Leung Kai-yan]

Re: Thinking of doing my first recap

Dear Friends,
The two above-mentioned motherboards. Thank you for your teaching!