new to the game and need some advice

[pnutbutters]

Hey everyone!

quick intro: been wandering the web for answers to various questions and i always end up at this site. So i decided to finally sign up and join the fun!

Just started getting serious into motherboard repair. I bought a ESR meter, and a hotair rework station. However I am slightly confused on a few things...

first, is what exactly can the ESR accurately test? Can I just use it on capacitors or can I use it on other components as well?

What is the "right" way to use the meter. For the smaller caps on the board I can not tell which is the positive and negative side...

Also, do I need flux? when do I use it? I have the resin core solder so do I still need flux?

I have a hard time telling if some of the empty spots on the board are from capacitors that have fallen off or they are suppose to be blank. Do i need the schematics for this or is there an easy way to tell?

What is the best type of thermal compound? And can you stack thermal pads if there is a gap when you only replace one thermal pad?

...I might have more questions but these have been bugging me for a while and I just want to get everything straightened out. I love doing this sort of stuff but never went to school for it so I am having trouble as I teach myself.

If you have any great references I should look at please point me in the right direction.

Thanks soooo muchhhhhhhh

[mariushm]

Re: new to the game and need some advice

ESR meter determines the internal resistance (in a very simplified way, it's more complex in reality) of a capacitor when energy goes through it. This resistance usually is more pronounced when capacitors are used with switching regulators and VRM and stuff that runs at high frequency (40-100 kHz). Regular multimeters don't use such high frequencies to test, that's why you need such a tool. Check Wikipedia's ESR page for a better explanation.

The right way is to desolder the capacitor and use the meter on it. In circuit the measurements are often wrong, because the capacitor can be in series or in parallel with other capacitors. The meter advertises that it can be used in-circuit but that only means using it won't activate other components in the circuits (such as diodes or mosfets), it's not a guarantee that the measurement will be correct.

Most ESR meters don't care about polarity, the one I have doesn't care about it. However, some do, in which case you have to pay attention at the manual and see if it says anything about it..

The negative side of a capacitor always has a bar colored differently than the rest of the capacitor cover or it has minus signs. In other cases, there's a - written on the PCB where the negative side of the capacitor is. Otherwise, there's a round circle with a small section blacked out - that's the negative side. Pay attention though as some companies use the opposite notation, where the black side refers to the + side (Asus for example)

Ceramic capacitors (those that aren't round) are often if not always bi-polar meaning they don't have a negative side.

Flux is a liquid that behaves like an acid, removing a thin layer of oxides from the top of the existing solder. Think of it like having a very, very thin sheet of paper between your solder tip and the solder on the PCB. It would be very hard for the heat to transfer from the solder gun tip to the solder on the board though this sheet of paper so you have a hard time turning making the solder on the board liquid.
When you apply a bit of flux, it acts like an acid eating those oxides and imperfections which prevent the heat transfer, it makes a hole in that sheet of paper, so now the solder tip touches the solder directly and everything heats up easier.

Most solder wire has a bit of flux in the middle, which is good when for example you want to solder, but it's often not enough for when you want to desolder something. To desolder something, you actually need to make the original solder liquid, and you do that by heating up the old one and maybe add some more solder there, so that it will come off with solder wick easier.

Through hole capacitors almost never fall off. If they did, you would still see the wires stuck in the holes. On surface mounted capacitors, if something falls, you can usually still see a bit of solder there - the pads are not perfectly flat, with a thin layer of solder on them, the surface is... "ugly"
It's perfectly normal for motherboards to have missing capacitors from the factory - the same layout is used for several models and the factory just takes out chips and parts to create different versions.. a budget one, a budget with few extras, a deluxe version and so on.

IMHO you shouldn't stack thermal pads if there's a gap - there shouldn't be a gap, maybe you're doing something wrong.


Spend the time to watch these clips to get a good tutorial on solder wires, flux and everything :

http://www.youtube.com/watch?feature...&v=J5Sb21qbpEQ
http://www.youtube.com/watch?v=fYz5nIHH0iY
http://www.youtube.com/watch?v=b9FC9fAlfQE

When you have the time, you should watch these as well.... it's a series of lessons made by Pace (it makes solder stations and other stuff) They're a bit outdated but they're very well done and everything he says is still valid:

1 : http://www.youtube.com/watch?v=vIT4ra6Mo0s
2 : http://www.youtube.com/watch?v=Mrhg5...feature=relmfu
3 : http://www.youtube.com/watch?v=_GLeC...hannel&list=UL

... and there's about 9-10 in total.. The very least you should watch parts 1, 4 and 6 ...