If i'm repairing a motherboard and it has 4 3300UF 6,3V capacitors broken...

  • Thread starter Thread starter CliscoCliso
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CliscoCliso

what else capacitors could i weld on the motherboard else ???

the capacitors are well solded right 2cm near the CPU socket,
what could change in soldered capacitors Voltage and UF do ???

supposedly i run 3.4Ghz CPU s478 ....
 
I see there are capacitors 3300UF with 16V and 25V easy to get ones,

what would be if i would solder them, i mean what frankly said would
voltage bahaving be ?


K.
 
CliscoCliso said:
what else capacitors could i weld on the motherboard else ???

the capacitors are well solded right 2cm near the CPU socket,
what could change in soldered capacitors Voltage and UF do ???

supposedly i run 3.4Ghz CPU s478 ....
Click to expand...

Capacitors have printed, and unprinted values. They must both
be considered, before making a substitution.

The best discussion on this, will be in the regulator chip datasheet.
It will have a discussion on the selection of "input capacitors" and
"output capacitors" for VCore.

The capacitor has working voltage (6.3V), nominal capacitance (3300uF),
but also has ESR and ESL (equivalent series resistance, equivalent series
inductance).

Electrolytic capacitor construction is such, that the volumetric
extent of the capacitor predicts the properties. Now, the funny
part of that, is when you look at the motherboard and the spacing,
you might see a smaller capacitor package size. When you go to shop
for an exact replacement, all the replacement caps are one size
larger and won't fit the gap. That makes repair difficult. It also
implies the properties of the capacitor, might not be up to
industry standards and norms. (The motherboard manufacturer always
seems to find the small ones, and then as a repair person, you
can't find any in that small size, only ones which are physically
larger. Since the capacitors are "shoulder to shoulder", they won't
fit.)

Where you live in the world, may also affect your repair choices. For
example, if I look at the most easily available suppliers here, they
don't carry any "premium" products I might be interested in buying.
I can find capacitors unsuited for a VCore regulator, easily enough
(Radio Shack). But if I look for capacitors especially designed for
switching regulators, I might have to shop via Ebay/Hong Kong, to
get product.

Start with the regulator datasheet, and work from there.

And replace an electrolytic, with another electrolytic. Don't try
substituting polymer caps, or OSCONs on your own. If you read the
datasheet, and see how complicated the equations are, you'll realize
why making substitutes is not a trivial task.

In terms of values, the value doesn't have to be exactly 3300. You
could use a 2200 for example. VCore allows some variation in value.
Using a different value, changes the output ripple, or the transient
response time. The capacitance is not the most important number.
If you raise the working voltage value (replace 6.3 with 16V for example),
all that will happen is the capacitor will become much larger
and won't fit on the motherboard.

If you use a capacitor manufacturer web site, you can get some
general comments on application of their components. Some of
these sites, have nice summary information to make it easier to
select the correct "family" for the job.

http://chemi-con.com/u7002/applications.php

*******

If you're curious, you can also look around this site.

http://www.badcaps.net/

HTH,
Paul
 
CliscoCliso said:
what else capacitors could i weld on the motherboard else ???

the capacitors are well solded right 2cm near the CPU socket,
what could change in soldered capacitors Voltage and UF do ???

supposedly i run 3.4Ghz CPU s478 ....
Click to expand...
I see there are capacitors 3300UF with 16V and 25V easy to get ones,

what would be if i would solder them, i mean what frankly said would
voltage bahaving be ?
Click to expand...

16V and 25V capacitors will work but may be too large in diameter or
length to clear the CPU heatsink/fan. 3300uf, 6.3V capacitors are
typically about 10mm diameter and 20mm long, while most 3300uF, 16V
capacitors are 12mm diameter. The only 10mm diameter 3300uF, 16V
capacitors I could find were 30mm long, and they were a low-quality
brand that you definitely want to avoid. Also you must use capacitors
rated for very low ESR. Some suitable brands and models are Panasonic
models FJ and FM, Nichicon models HM, HN and HZ, Sanyo (now Sun
Electric) WG, United Chemicon/Nippon Chemicon KZE (KZG and KZJ are not
considered reliable in the long term), Rubycon models MBZ and MCZ, and
Samxon model GC. Do not buy counterfeits.

You should be able to substitute solid polymer capacitors around the
CPU, and because these capacitors have lower ESR ratings, you can use
lower capacitance values, as little as half the original values, and
some 6.3V capacitors can be replaced with 2.5V or 4V solid polymers.
However you absolutely must verify that it's safe to use lower voltage
capacitors for your particular motherboard. What brand and model
motherboard do you have? Here's a description of a "poly mod" for a
Dell GX620, which also uses a Pentium 4:

http://www.badcaps.net/forum/showthread.php?t=9504
 
Capacitors have printed, and unprinted values. They must both
be considered, before making a substitution.

The best discussion on this, will be in the regulator chip datasheet.
It will have a discussion on the selection of "input capacitors" and
"output capacitors" for VCore.

The capacitor has working voltage (6.3V), nominal capacitance (3300uF),
but also has ESR and ESL (equivalent series resistance, equivalent series
inductance).

Electrolytic capacitor construction is such, that the volumetric
extent of the capacitor predicts the properties. Now, the funny
part of that, is when you look at the motherboard and the spacing,
you might see a smaller capacitor package size. When you go to shop
for an exact replacement, all the replacement caps are one size
larger and won't fit the gap. That makes repair difficult. It also
implies the properties of the capacitor, might not be up to
industry standards and norms. (The motherboard manufacturer always
seems to find the small ones, and then as a repair person, you
can't find any in that small size, only ones which are physically
larger. Since the capacitors are "shoulder to shoulder", they won't
fit.)

Where you live in the world, may also affect your repair choices. For
example, if I look at the most easily available suppliers here, they
don't carry any "premium" products I might be interested in buying.
I can find capacitors unsuited for a VCore regulator, easily enough
(Radio Shack). But if I look for capacitors especially designed for
switching regulators, I might have to shop via Ebay/Hong Kong, to
get product.

Start with the regulator datasheet, and work from there.

And replace an electrolytic, with another electrolytic. Don't try
substituting polymer caps, or OSCONs on your own. If you read the
datasheet, and see how complicated the equations are, you'll realize
why making substitutes is not a trivial task.

In terms of values, the value doesn't have to be exactly 3300. You
could use a 2200 for example. VCore allows some variation in value.
Using a different value, changes the output ripple, or the transient
response time. The capacitance is not the most important number.
If you raise the working voltage value (replace 6.3 with 16V for example),
all that will happen is the capacitor will become much larger
and won't fit on the motherboard.

If you use a capacitor manufacturer web site, you can get some
general comments on application of their components. Some of
these sites, have nice summary information to make it easier to
select the correct "family" for the job.

http://chemi-con.com/u7002/applications.php

*******

If you're curious, you can also look around this site.

   http://www.badcaps.net/

HTH,
    Paul
Click to expand...


I have understood what is about capacitors, seems i'm not going to
repair the MBO so easy, but i will do my best,
having some spare motherboards, so i'll find the appropriate ones.
This what you just typed is a wide area which is a new area for me...

thanks for open-minding...
 
I have managed to solder them 3pcas, but i had have problems with
unsoldering the previous faulty ones,

i had made mistakes on the mbo pcb due to close wire contacts under
the painted pcb...just the soldering device was to strong 40W Weller
for the unsoldering job,

For soldering i could have use a 20W device as this melted the
contacts around the condenstors...


thanks for tips ...
 
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