Newb asks eye-rolling questions.

[Kessler]

So after doing the software and basic hardware side of computer repair for years, I figure it's high time I learn how to properly replace those 2-3 bad caps rather than throwing an otherwise good board in the garbage.

I'm in Canada and just ordered a Weller WES51 soldering station which should be here tuesday.

1) That leaves me with 2 questions. What is the best multimeter for doing motherboard repair priced between $40-75. I've seen a few that measure capacitance but their upper limit is 200-400uf (which makes them pretty much usesless, correct?)

2) If you were going to order $30 or so worth of caps to start off with, what would be a good all purpose selection of size and spec? I understand I can use a 1000uf to cover all the lower sizes but I'm still a little confused about voltages. Also, is width only a limitation when caps are close to each other?

I'm learning so go easy on me The last electronics course I took was in grade 9 so I have no memory of it.

I already have a good selection of solder, a desoldering pump and wire, picks etc. Anything else I'm missing??

[i4004]

Re: Newb asks eye-rolling questions.

1. you wanna measure esr(ohms) and to that extent i would suggest esr micro
contact this guy
https://www.badcaps.net/forum/member.php?u=12802
it's essentially rather simillar to atlas esr
( http://www.peakelec.co.uk/acatalog/jz_esr60.html ), but much, much cheaper

offcourse, you can get anatek blue
http://www.anatekcorp.com/blueesr.htm
but it seems that with kits they have a tendency to misplace parts etc.
also, it can't measure capacitance...

either way, you need to know esr...

[Kessler]

Re: Newb asks eye-rolling questions.

1. you wanna measure esr(ohms) and to that extent i would suggest esr micro
contact this guy
https://www.badcaps.net/forum/member.php?u=12802
it's essentially rather simillar to atlas esr
( http://www.peakelec.co.uk/acatalog/jz_esr60.html ), but much, much cheaper

offcourse, you can get anatek blue
http://www.anatekcorp.com/blueesr.htm
but it seems that with kits they have a tendency to misplace parts etc.
also, it can't measure capacitance...

either way, you need to know esr...

So, can caps be tested on the board or do they have to be pulled? It seems to me that if I have already pulled the cap I'm going to be putting a new one on regardless.

[Gianni]

Re: Newb asks eye-rolling questions.

You can measure caps on board but the measure is not accurate, especially when you have some caps in parallel.
Of course if they are damaged (ESR out of spec) you can discover it easily with an ESR meter.

Question 2: I don't believe you can cover all lower size with 1000uF, at least I will not replace a 220uF with 1000uF and some time you have not enough space.

I have not recapped a large number of board, anyway in my little experience I have seen most common value are 1000uF 6.3-10V, 1500~3300uF 6.3-10V, 1000~2200uF 16V.

If I were you I will buy caps based on the PSU or MOBO I have to recap.
You can see some premade kit for some MOBO and get an idea of what type of caps are used.

By the way you can buy caps from Topcat, the owner of Badcaps.

Ciao
Gianni

[PCBONEZ]

Re: Newb asks eye-rolling questions.

To do it right you need:
An ESR meter.
A resistance meter.
A capacitance meter.
On the uF meter, 0-5000uF would be best. [Get those occasional tiny's and 4700uF that show up questionable.] At least something that can do 220uF to 3300uF because those are common.

For ESR, low is good but there are some problems checking it.
Very high grade caps have ESR below .01 and that's below the range of most ESR meters. [At least those that aren't 100's of $$.]
In that case the meter might show ESR as Zero and everything is fine.
- But Zero on an ESR meter would also show up if the cap is shorted, and that's bad.
You need to check with a regular resistance meter too in order to be sure.
ESR Ohms should be low and DC Ohms should be high [after the cap charges from the meter].

The voltage marked on a cap is a limit like a load rating on a rope.
It's okay to use higher volt caps in a circuit with a lower voltage just like it's okay to use a rope to lift less than it's rated weight.
-
Be advised though that use of a cap on a lower voltage will effectively turn the cap into a lower voltage cap. This is because the thickness of the Oxide layer [which is the actual Dielectric in Electrolytic caps] will adjust in thickness based on the applied voltage. The technical term is "Re-formed", as in the layer is re-formed to a new thickness. [This only matters to people that salvage caps for re-use which in some parts of the world is the only way to get decent caps -and- is sometimes done temporarily to verify the board is worth buying replacement caps for.]

If you only have $30 to throw at caps you are better off waiting to see what you need and then ordering them. [Yeah, waiting sux but so does having the wrong size in stock and having to order and wait anyway.]

A cheapie multimeter [for DC Ohms anyway] is good enough for resistance checks or tracing circuits because you aren't looking for a specific number, just the gross condition. Open, short, high, low. - Doesn't have to be very precise, just correct.

For PSU/Mobo voltage checks a basic non-junk one should do just fine.
Should be good to at least +/- 0.1 VDC and +/- 0.01 VDC would be much better.

Caps in parallel with other caps have to be pulled for ESR checks.
For DC Ohms or uF checks they should be pulled.
Yeah, I know the ESR meter ads say you don't have to pull caps but on motherboards that's usually bunk.
.

[Kessler]

Re: Newb asks eye-rolling questions.

To do it right you need:
An ESR meter.
A resistance meter.
A capacitance meter.
On the uF meter, 0-5000uF would be best. [Get those occasional tiny's and 4700uF that show up questionable.] At least something that can do 220uF to 3300uF because those are common.
..

Very informative post, thanks!

So if I grab an average multimeter that does resistance, and capacitance to at least 5000uF and an ESR meter, I'm set.

[i4004]

Re: Newb asks eye-rolling questions.

but where will you find multimeter that does up to 5000uF?
usual range of cheap multmeters is up to 20uF.

then you have much more expensive meters that do just capacitance, and which have enough range.

offcourse, you also have esr micro that does both esr and capacitance for 55$..heh...
http://preher-tech.com/esrmicro.aspx
(that's older version, that was 45$)


on top of that just a cheap multimeter, yeah.

(offcourse, if you can find multimeter that does up to 5000uf more power to you!
then indeed only it and esr meter)

>It seems to me that if I have already pulled the cap I'm going to be putting a new one on regardless.

in that case you don't need any of above-mentioned instruments, right?
<wink>