Capacitors

[Venomus28]

Hello Forum
I have a question to ask and i am sure it will interest to others also.
Usually our supply store doesnt have the exact voltage, or capacity as the old capacitor we are going to replace
So we usually get offered another capacitor in a higher voltage or higher capacity.
So for example today i got a 10V 2200uF instead of the 6.3V 2200uF as it was the bulged one

What i am asking is, what is the safe range we can exceed or outnumber those two values without causing damages ?

Thank you

[mariushm]

Re: Capacitors

It depends on the circuit, on the location of the capacitor.
Often, you can use capacitors with higher voltage rating but you have to be careful about the diameter and height of the new capacitor.

In some circuits, more capacitance doesn't hurt, and in some situations you could even use capacitors with lower capacitance if they're of different type (polymer capacitors instead of electrolytic capacitors), it depends on why a specific type and size of capacitor was used in that circuit.

However, if you don't know or you're not sure, it's better to stick with same capacitance and type of capacitor.

PS. Be careful when replacing capacitors, motherboards in particular require capacitors with very low ESR. The new capacitor's ESR should be very close or lower than the old capacitor's ESR value.. you can find those values in the datasheets for those capacitors (in the impedance at 100kHz column)

The show may recommend you a capacitor suitable for power supplies (to filter 5v output) and such capacitor has low ESR but may not be low enough to be suitable for the CPU VRM on a motherboard, for example.

[junktv]

Re: Capacitors

Lol i heard today that temp is the most important thing. All caps are made by one manufacturer and just relabeled. Oh and esr doesn't matter I heard from 2 places.

Stick around here these guys will give you good info.

[PeteS in CA]

Re: Capacitors

If it's just decoupling an IC, the main consideration is fit and that it's a 105°C part. Given the not so great reliability of general purpose 105°C parts I've heard of around here I'd suggest using older low impedance series parts, such as Nichicon PW, Nippon Chemi-Con LXZ, Panasonic FC, or Rubycon YXF series parts.

For PSUs and MBs fit and getting close to the impedance of the original are the main considerations. On equipment that is several years old that could be an interesting opportunity. If a newer, lower impedance series is on the market, the higher voltage part in the new series might be the same impedance as the lower voltage part in the older series.

With PSUs, the output capacitors are usually 5000-10000 hour rated series. This means that at the maximum rated ripple current and temperature the parts will last the rated hours or more; the actual life increases dramatically at lower temperatures. The output areas of modern, high quality, PSUs is super dense, with output capacitors squeezed in between the clusters of output harness wires and hot heatsinks and output inductors. Don't substitute 2000-3000 hour parts for 5000-10000 hour parts, if you want long life. On the other hand, if it's a temporary repair or long life isn't a consideration, mature, shorter life low impedance series like Nichicon PS or PM should get your PSU running again.

[Venomus28]

Re: Capacitors

Thank guys
Im very happy being part of this forum
Usually my repairs are and have been, monitors, psu and motherboards
and ive always tried to get part with the same capacitance and voltage, but never payed attention to the temp ...

[ChaosLegionnaire]

Re: Capacitors

the proper usage and application of caps is quite similar to that of medicine.

in medical school, all prospective medical practitioners have to sink into their brain this basic concept that there is actually no strict division of between medicine and poison. medicine when used correctly IS medicine. medicine when used incorrectly is poison. this brings to mind the michael jackson sleeping drugs overdose case, the joan rivers anaesthetic drug allergy case and the legalisation of narcotic drugs though that discussion is meant for the vip room, so i will save it for that.

some time back, one of our members, Stefan Payne, lectured and tongue lashed some guys in a computer forum who didnt know how to properly recap their psu with the right caps and the system got worse and even more unstable after recapping!

so to sum it up in one phrase: caps when used properly, will make your system run 100% smoothly. use the wrong caps and u are worse off not recapping at all... to paraphrase that in medical terms: medicine when used properly, will make your body run 100% smoothly. use the wrong medicine and u are worse off not taking any medicine at all...

[Venomus28]

Re: Capacitors

So you mean that i have to strictly stick to the old ones as for value and capacitance and not risk.