Help

[Danyom Berhane]

I have a dell optiplex GX270 computer with dead caps in it. The computer would shut down every 2minutes or so. I changed all the faulty caps with the exception of three 1800uf@16v capacitors (those are found at the back of the CPU). I couldn't find capacitors with such specification. I have three 2200uf@16v caps. Is it okay if I replace a 1800uf,16v capacitor with a 2200uf,16v? If there are some risks involved what are they?
apprecite your effort
Danyom

[PCBONEZ]

Re: Help

Safe move.

As long as they are low ESR caps 2200uf,16v should be fine in place of 1800uf,16v.
In fact overclockers make similar mods all the time.

Caps are +/- 20% on the uF and as they age uF goes down.
The 2200uF is just barely over 20% of 1800uF and as they age they will get closer to 1800uF anyway.

.

[Leung Kai-yan]

Re: Help

I have a dell optiplex GX270 computer with dead caps in it. The computer would shut down every 2minutes or so. I changed all the faulty caps with the exception of three 1800uf@16v capacitors (those are found at the back of the CPU). I couldn't find capacitors with such specification. I have three 2200uf@16v caps. Is it okay if I replace a 1800uf,16v capacitor with a 2200uf,16v? If there are some risks involved what are they?
apprecite your effort
Danyom

Dear Friend,
It is good to replace all the capacitors of your mainboard because the bad capacitors have no viewable sign always!

[Danyom Berhane]

Re: Help

Thnx fellas I'll keep you posted on the result tho I don't know what ESR means,
so long

[bgavin]

Re: Help

PC gives good advice.

The rule of thumb is replace everything from 470uF and up. Go higher in capacitance, not lower. OK to use higher voltage rating, such as 10v in place of a 6.3v cap.

[PCBONEZ]

Re: Help

ESR = Equivalent Series Resistance
-
[The following is not 100% technically accurate but it's close enough for a non-tech/non-engineer.]

ESR to a capacitor is kind of like what resistance is to a resistor.
[Meaning it is a measure of opposition to current flow.]

Unlike resistors, capacitors charge and discharge and they also respond differently at different frequencies, temperatures, and levels of charge. It's impossible to accurately measure a resistance yet they do have some opposition to current flow.

ESR is basically what the resistance of a capacitor would be, if it were a resistor, to cause the same amount of opposition to current flow as that size resistor would.
(Again, unlike 'real' resistance, it changes with frequency.)

Motherboards (and such) use capacitors to send noise (small high frequency voltage fluctuations called ripple) out of the circuit. They use capacitors with very small ESR (low 'resistance' to noise) to get as much noise out of the circuit as possible.
- Use of normal or high ESR capacitors would leave more noise in the circuit and that noise (remember it is voltage fluctuations) may cause erratic operation of components (CPU, RAM, Chipset) or even data corruption.

Please note: ESR will be different for different frequencies and temperatures.
The standards used in data tables are 100 kHz and 20°C. - Units will be in Ohms.
[Without a standard there would be no way to compare different capacitors.]
-
It's not always called ESR in data sheets, it may say:
"Impedance at 100 kHz at 20°C"
"Ohms at 100 kHz at 20°C"
"Z at 100 kHz at 20°C"
Or possibly something else.
(Regardless of the name used it's easy enough to figure out which column is it by Ohms, 100 KHz, and 20°C all in one place.)

-

Hope that helps!

.

[Krohling]

Re: Help

PCBONEZ, that's interesting.

Are there any other tips on how to spot "Low ESR" caps
I ask that because I'm having a hard time finding a number of options.

I found in stock only one cap from Xicon called "low ESR" @ www.mouser.com
Farnell wasn't very helpful either, fond only 1 from Panasonic. I'm looking for 1000uF 16V caps.

[PCBONEZ]

Re: Help

Best thing to do is find the manufacturer's data tables and just look.
You can find most with google.

This site sells a kit for that exact motherboard.
https://www.badcaps.net/pages.php?vid=21
He usually will also sell caps individually.
[Select 'custom kit']

If you are outside the USA or Canada this guy sells caps.
https://www.badcaps.net/forum/member...tposter&t=4793

When comparing the ESR of one series/model of capacitor to another look at the can size. [diameter x length]
Usually all capacitors in the same series have the same (or close to it) ESR for all the caps in the same can size.
Also (in the same series) a bigger can usually means lower ESR.

If you will tell me/us what the series (model) of the original caps are (and the uF / Volts / diameter ) then we can tell you what the ESR was on the original caps.
[Many people here have the data sheets found and downloaded already.]

.

[i4004]

Re: Help

ESR = Equivalent Series Resistance
-
[The following is not 100% technically accurate but it's close enough for a non-tech/non-engineer.]

ESR to a capacitor is kind of like what resistance is to a resistor.
[Meaning it is a measure of opposition to current flow.]

Unlike resistors, capacitors charge and discharge and they also respond differently at different frequencies, temperatures, and levels of charge. It's impossible to accurately measure a resistance yet they do have some opposition to current flow.

ESR is basically what the resistance of a capacitor would be, if it were a resistor, to cause the same amount of opposition to current flow as that size resistor would.
(Again, unlike 'real' resistance, it changes with frequency.)

Motherboards (and such) use capacitors to send noise (small high frequency voltage fluctuations called ripple) out of the circuit. They use capacitors with very small ESR (low 'resistance' to noise) to get as much noise out of the circuit as possible.
- Use of normal or high ESR capacitors would leave more noise in the circuit and that noise (remember it is voltage fluctuations) may cause erratic operation of components (CPU, RAM, Chipset) or even data corruption.

Please note: ESR will be different for different frequencies and temperatures.
The standards used in data tables are 100 kHz and 20°C. - Units will be in Ohms.
[Without a standard there would be no way to compare different capacitors.]
-
It's not always called ESR in data sheets, it may say:
"Impedance at 100 kHz at 20°C"
"Ohms at 100 kHz at 20°C"
"Z at 100 kHz at 20°C"
Or possibly something else.
(Regardless of the name used it's easy enough to figure out which column is it by Ohms, 100 KHz, and 20°C all in one place.)

one of the best simple explanations i've seen on the subject.

excellent.

[kc8adu]

Re: Help

since you didnt know and understand this before you recapped i bet you have general purpose caps in your board now.
just order the kit and use it.
gp caps will have a very short life in a 270.