(OT) Solder help

[kulcousy]

I don't know where to ask this.
Could someone define a minimal setup for testing and replacing fuses on a motherboard? I have alot of non-functional boards have a basic grasp of the electrical principles and components.
Thanks,
John

[Neil]

I have recently been trying to replace a very tiny fuse on a T30 motherboard. IMHO, many of the components on a motherboard (this particular fuse for example), a just too small to work with. My tool kit includes a fine tipped 25W soldering iron, and 5X magnifying glasses. I don't have anything to hold the components in place as I try soldering, as all these laptop motherboard use surface mounted components. They don't have pins that go through holes and can be soldered on the underside of the board. But my soldering iron is just too big anyway.

I've tried on three different occasions, thinking if only I could...it would work. But each time I end up frustrated, having done more damage than good. And reinforcing the realization that this stuff is just too small.

If you are skilled in micro surgical procedures, for example, and have the right tools, you might be able to master this. If so, I have a couple of T30 motherboards that you can practice on. I give up!

[wap32]

A good, fine-tipped soldering iron (I use Antex but I hear Weller is pretty good), good light, and IMO, the most important tool, a good pair of tweezers for smd work, like this (Vomm and Lindstrom are pretty good).
If your eyesight is good enough, a magnifying glass is not needed.

EDIT: thin solder is also recommended (1mm or thinner) and desoldering braid might also come in handy.

[kulcousy]

Gee Neil don't give up. Have you tried the suggested method from Wap32?
People often post routinely replacing fuses and it's far from routine but it seems with a small enough like the Weller WM120 it's doable.
However... no magnification? I can't remember my eyes ever being good enough to go that route.
Thanks Wap32
John

[Neil]

I've successfully repaired a few T23 machines with the loose inductors. They are not too small. And, there are fuses on the T30 board large enough that I think I could work with 'em. But the one I was trying to replace is right next to the LCD cable connector, and is about the size of a flea, seriously. It looked like a black speck to me without magnification. But, with the magnifier I could clearly read the "F" on top of it. Still it felt like attempting open heart surgery on a flea. Just the slightest flinch (yes I was trying to use small tweezers) and that little flea would jump out of my field of vision (not very hard with those 5X glasses on). I actually lost a couple of spare fuses that way. Just don't know where they jumped off to. Had to pull another off the spare parts board.

And, yes, I have given up on this particular board. I'll probably attempt other soldering jobs on motherboards, just not this one! Or any other if the components are this tiny!

[richk]

Starting somewhere in the time between T40 and T43, they changed solder formula to "get the lead out". The temperature required to do the work is now much higher. It is difficult to work on the newer boards without more sophisticated equipment.

[rkawakami]

A general recommendation on "replacing" a bad surface mount fuse goes something like this: "put it on top of the old fuse".

Usually the surface mount fuse has metal endcaps which extend to the top surface of the package. If you apply a tiny amount of solder (the stuff I use is about 0.5mm in diameter) to the top on one end of the old fuse, you can then hold the new fuse in place with a small flat-bladed screwdriver, dental pick, toothpick, etc, and then heat the junction between old-and-new. After that side is held firmly in place, you can then heat the other end of the fuses with the soldering iron and a tiny bit of solder.

I've used the same technique to stack a couple of surface mount capacitors together, the last time just today in fact. It does take a steady hand and some good eyes, but more importantly, you need to have a fine-tipped soldering iron, temperature controlled if possible, and some thin (lead) solder.

[SMA]

Found this at avrfreaks.com
Low Cost SMD Soldering Guide