Replacing one capacitor with 2 capacitors

[phoenixlament]

I have a dead(leaking) capacitor rated at 1650uF, 16V. After looking through my pile of dead electronic stuff, I failed to find another similarly rated capacitor at 16V or higher.

However I'm thinking of creating a combination of 1650uF with a 1000uF and a 650uF, both of which I have.

Now, according to textbook theory, when capacitors are placed in parallel, C(total)=C1+C2+C3...

I'm thinking of soldering on two insulated wires in place of the dead cap, and soldering in the two caps in parallel and insulating the leads off.

Would this work? Thanks

[Toasty]

Re: Replacing one capacitor with 2 capacitors

In theory, you are correct. Both must be at least 16v and if both caps are good, you will get your 1650uF.

>>I'm thinking of soldering on two insulated wires in place of the dead cap, and soldering in the two caps in parallel and insulating the leads off.<<

Can't properly answer that until you tell us what type of circuit are you subbing them in?

Please, what was the make & series of the original cap?

Toast

[phoenixlament]

Re: Replacing one capacitor with 2 capacitors

lol, it was a TNR fuhjyuu (M) P10. yeah i got fuckjyyued.

the replacement caps i pulled also happen to be fuhjyyus too, except they are working. and after what i've read from here, i'm gonna change my mind about replacing fuhjyyus with fuhjyus. (i know ur laughing at me but hey its only my second post, so forgive me for my noobiness please )

Anyway this cap belongs to a ATX power supply, and it regulates the -12V rail. Due to the cap leakage, the rail is only giving ~11.58v.

Two other bad fuhjyyus(470uF,16v) regulating the +5vsb (standby rail) have lowered the +5v to ~2.2v. Other than these two sagging voltage rails, all other voltages are fine and within range.

I was going to replace the +5vsb regulating caps with good fuhjyyus but don't think that would be wise after reading up on fuhjyyu history.

The hunt continues for a good 1650uF,16v and two 470uF,16v replacements

[370forlife]

Re: Replacing one capacitor with 2 capacitors

If you are in the US, digikey has a excellent selection and very fast shipping.

This is a good replacement for that 1650uf.

These will also be good replacements for the two 16v, 470uf caps.

But you really should replace all the caps.

[yanz]

Re: Replacing one capacitor with 2 capacitors

i would replace it with 1500uF or 1800uF 16v. you said it was for -12v, then dont bother, 1000uF 16v will be enough. use a good low esr series, though..

2x 470uF can be replaced with 2x 680uF if you found ones..

btw, FC is a good series, but the last FC i can find is from 2001 - 2002 date code.. i would prefer FM (newer).

[phoenixlament]

Re: Replacing one capacitor with 2 capacitors

If you are in the US, digikey has a excellent selection and very fast shipping.

Thank you all for your fast replies. 370, I checked out your links. Do the prices listed on digikey include shipping fees as well?

Also, this power supply is for a good old Pentium 3 computer, and it's really not feasible spending anything repairing it since I have a access to a pile other discarded hardware on campus (and their parts)

So I've decided to pull two 470uF,16v good teapos from a discarded Socket462 motherboard, circa 2002. Are Teapos from that time alright?

[phoenixlament]

Re: Replacing one capacitor with 2 capacitors

i would replace it with 1500uF or 1800uF 16v. you said it was for -12v, then dont bother, 1000uF 16v will be enough. use a good low esr series, though..

2x 470uF can be replaced with 2x 680uF if you found ones..

btw, FC is a good series, but the last FC i can find is from 2001 - 2002 date code.. i would prefer FM (newer).

Thanks for your input. What is the typical percentage tolerance level for replacing caps? And how come when a 1650uF is for -12v, you can use a 1000uF?

And how come 2x 470uF can be replaced with 2x680uF?.. that's roughly 30% difference.

Just curious.

[370forlife]

Re: Replacing one capacitor with 2 capacitors

I assume this is a antec CWT unit, so it could actually run its ratings after a recap and run a lower-end p4 machine.

Newer teapo's are ok in power supplies, they do good ripple suppression, lifespan is probably shorter than good companies like Nippon Chemi-con, Rubycon, Nichicon, or Panasonic. They are bad on motherboards, especially older ones. I wouldn't use them.

The cost of those caps does not include shipping, but on a order that small it shouldn't be much. Digikey has very very fast shipping, too.

Going up in rating on the caps is ok to do, usually will give you better filtering. You don't want to go super high with it, like a 3300uf in a 470's space, as its not going to be much different than a 680uf.

And, since the -12v and -5v (assuming it has it,) are so little used and have such little current, you don't need that much uf to filter it.

[phoenixlament]

Re: Replacing one capacitor with 2 capacitors

Thanks for the info, 370. will take it into account.

Just wondering - how does a cap's ability to take and release charge have anything to do with filtering currents on a rail? And how come bigger capacitances are better?

[370forlife]

Re: Replacing one capacitor with 2 capacitors

I'm not that advanced in capacitors, but my general understanding is that it is like a rechargeable battery. The current going into the battery may fluctuate rapidly (ripple) but the battery will still charge to a certain level, and when you pull current from the battery, it is constant and clean.

That's just from what I understand, I could be wrong, a more advanced poster here may be able to fill you in better.

As for uf, all I know is that the more current you have, the more you need, at least at the DC output side of the psu. Its true for the AC side, too, a larger wattage psu needs a higher uf rated cap, like 680 or 1000uf, if it is non-APFC. Most APFC units use just 330uf or so caps.

[Topcat]

Re: Replacing one capacitor with 2 capacitors

I replace 1650uF caps with 1800uF caps all the time in PSU's, never had a problem.

[yanz]

Re: Replacing one capacitor with 2 capacitors

Something's telling me that your 1650uF caps is not for -12v rail, but for +12v rail. I remember having seen 1650uF caps 16V in PSUs many times before and they were not for -12v rail. (I could be wrong though)

So, maybe you can check it again with your multimeter?

If it's indeed for +12v rail, you can :

• Change it with 1800uF / 1500uF. 1500uF is probably easier to find in your junk pile. Using a used/recycle caps isn't recomended though.
• If there's room for a 12.5mm (diameter) cap, use a 2200UF/3300uF 16v 12.5mm caps. It will have lower ERS compared to 1650uF caps (assuming comparison within the same series). This is better if u intend to use the PSU in P4 system that need more stable and capable of +12V rail.
• Using 1000 + 680 uF caps in theory is doable (like what Toasty said). But do it only when there's no other available option, or for emergency/immediate rescue. Reason is that room in secondary area of PSU is so tight, if not carefull, cables will wreck those tandem caps.

And to add 370forlife's explanation, that ometimes we can't always get what we need (or we think we need). But by combining :
- understanding of how the circuit and components work
- years of experience and deep observation/researching of what components used in electronic device
- what part/components you have or what is available..

.. you can choose to do something different but still safe, or even better (in safety and performance)

[phoenixlament]

Re: Replacing one capacitor with 2 capacitors

Sorry for the late reply. I've been working like crazy the last couple days.

Thanks for the analogy, 370 and yanz. I was always curious why there were so many capacitors everywhere..

Forgot to post this earlier - this PSU is a Sunny Technologies 300W ATX 2.03.

Update:
I've fixed the +5VSB problem(two leaking 470uF caps) with two replacement Teapo 470uF/16V capactiors. 5V rail registers at exactly 5.05V, very nice.

Todo:
Still haven't found a 1500-2000uF/16V capacitor replacement yet. I'll be hounding around the discarded electronics dump on campus and I'll definitely post when I find one.

Yanz: Re-tested the +/-12V rails with multimeter. +12V rail is at 11.60V (barely within +/-5% range. -12V rail is at -10.71V, out of acceptable range.

I understand that it's best not to reuse caps but this is only a 300W power supply, and when fixed it will be just powering a Pentium 3 "Learn Linux machine".

[370forlife]

Re: Replacing one capacitor with 2 capacitors

those are terrible voltages, sorry. 11.6 is at the very bottom of the atx spec for the 12v.

Definitely get those caps.

[yanz]

Re: Replacing one capacitor with 2 capacitors

yup, 11.6v isn't good, but did you turn on the psu with no load? some psu need a certain amount of minimum load so that its rail could 'behave' well.

lets just forget bout the -12v. a -10v or more on your dmm display might be frightening but in my experience it's not rare for even a healthy cheap psu to screwed up on the -12v rail, while all other rails were good.

what i suggested was that for you to recheck if that 1650uF cap was for +12v rail or not. (but i think it is..)

if you could find a p4 mobo, there should be some 16v caps (1500 - 2200uf) near I/O ports.

if u are my neighbour, i could give you some 1500uf/16v Sanyo WG or NCC KZE just to see if it will fix the problem. i hate to see an unfinished project, just like reading a good novel just to see the last ten pages missing.

i can send you that 16v cap by mail (will take maybe 30 days or more to arrive), just pm me. or get it from your junk or buy it locally/online. or maybe you guys in america can send him one

happy searching..!