parhelia512 wrote:

But i've noticed something strange under the BIOS voltage screen : The VTT (1,5V) is fluctuating a lot : from 1.31V to 1.72V. I don't know if this could be the problem ?

Bad small caps in the VTT voltage regulator can do this.
They are usually 4 or 5 mm and 10 or 22 uF.

parhelia512 wrote:

Is there a way to test a capacitor once unsolded ?

To do it correctly you need to check ESR and capacitance and resistance. Resistance both ways.
If you only have a resistance meter you can still sort-of check them the old ways but it will not find all possible problems.
An analog meter works best but a DMM can work too. Just not as easy.

The old ways.
DISREGARD THEIR METHOD ONE. Their method one is both dangerous and stupid.
https://www.electricaltechnology.org/2013/06/ … th-digital.html
.

Hi PCBONEZ and thanks for your answer

Do you know where i can find those capacitors ? Near the SLOT1 ? Between SLOT1 and memory ?

Thanks 😀

PCBONEZ wrote:

The old ways. DISREGARD THEIR METHOD ONE. Their method one is both dangerous and stupid. https://www.electricaltechnology.org/20 […]
Show full quote

The old ways.
DISREGARD THEIR METHOD ONE. Their method one is both dangerous and stupid.
https://www.electricaltechnology.org/2013/06/ … th-digital.html
.

Yeah, their method one makes no sense. If it doesn't fail in dramatic fashion, the cap will charge to 100% Vpp 60 times a second and you will learn nothing.

Use ESR meter. I have two, one at work and one at home. So useful to quickly fix monitors and tv crt and power supplies, motherboard. Capacitors has to be removed first.

Not too expensive to get. It is about 120Khz signal and is measured by the DAC on the chip and reported in ESR value and you check against good values chart.

Cheers,

I am not sure which cap(s) you mean.
Give me uf volts and diameter.

Good places to get caps depend on where in the world your are.
Overseas shipping can cost a lot more than the caps for small orders.
(I used to buy in boxes of 500 or 1000 and sometimes 10,000 in an order.)

In the US there is Digikey, Mouser, Newark and BDent.
I haven't looked at overseas options for quite a while... I remember Farnell and RS-Components were popular.
Newark is associated with Farnell and was absorbed by Avnet a while back. That seems to be an improvement.
There are others on both sides of the pond but their stock of Low ESR AL-Lytic caps is usually limited or none.
.

pentiumspeed wrote:

Use ESR meter. I have two, one at work and one at home. So useful to quickly fix monitors and tv crt and power supplies, motherboard. Capacitors has to be removed first.

Not too expensive to get. It is about 120Khz signal and is measured by the DAC on the chip and reported in ESR value and you check against good values chart.

Cheers,

There is a lot of advertising about those being able to check in-circuit.
That usually isn't true on motherboards because of other caps in parallel.
Even when it looks like there is only one cap there is usually a small SMD cap in parallel to handle higher frequency EMI.
On motherboards it's best to pull the caps and them check out of circuit.
.

To be clear, testing in circuit will give you a measure of impedance which must be as low or lower than the actual impedance of the capacitor. If the ESR measurement is high in circuit for any given cap, the cap is definitely bad. If it measures good in circuit, the real ESR of the cap might be being masked by another cap in parallel and may still be bad.

In short, pop out one leg when testing to be sure.

pentiumspeed wrote:

It is about 120Khz signal and is measured by the DAC on the chip and reported in ESR value and you check against good values chart.

Yes, I know how they work.
I have one of the typical entry level I built from a kit, a Sencore Z-Meter and a newer professional one that retailed for around $850 when I got it.
If I had to chose 1 it would be the entry level because it's far easier to use and it gets the job done.

I kind of read right past that quoted part.
120kHz is an odd number to see for an ESR meter. Are you sure you didn't mean 120Hz?

For Low ESR motherboard caps the Ripple and Impedance ratings shown in the datasheets assume the test frequency is 100kHz.
If you are not using 100kHz there are conversion factors for other frequencies in the datasheet somewhere. (There should be anyway.)

That chart is for general purpose caps and it doesn't always work well for low ESR caps.
I haven't looked at one of those in a long time though, so maybe they have changed the charts.
.

PCBONEZ, sorry for my bad english.

I meant which capacitors are involved in the VTT regulation on the motherboard PCB ?
Maybe i can try heating it to make new solder points ?

parhelia512 wrote:

PCBONEZ, sorry for my bad english.

That's okay. Everyone here is used to it.

parhelia512 wrote:

I meant which capacitors are involved in the VTT regulation on the motherboard PCB ?

I see.
I can not tell you which ones are VTT without tracing the circuit.

To do that you need the pin-out (schematic) for the chipset.
Find the pin for VTT into it, and follow the circuit to find the regulator.

That is too much work or takes too much time for most people so they just replace all the caps.

parhelia512 wrote:

Maybe i can try heating it to make new solder points ?

I am not sure what you mean.
.

I found a capacitor that had solder problem...maybe these small capacitors have the same problem and heating the solders will help the problem ?

parhelia512 wrote:

I found a capacitor that had solder problem...maybe these small capacitors have the same problem and heating the solders will help the problem ?

I think you mean a cold-solder joint.
Yes, resoldering those can help.

Works best if you add some fresh solder when you do it.
Only a small amount though.
.

Yes, a cold solder joint.

OK, thanks. We are talking about small rectangular capacitors ?

A cold-joint is a broken connection.
It does not matter what it's on.
.

Yes, i understand.

I was talking about the capacitors involved in the VTT regulation.