Capacitor substitution question: 35V for 6.3V okay?

[Ben Morehead]

As I was wrestling with a half-inch water cooling hose, I broke off a
capacitor on my brand-new (never-powered-on) MSI motherboard. The cap
says 1000µF, 6.3v 105C. Radio Shack has a similar looking cap with the
following specs: 1000µF 35V 20% Radial-lead Electrolytic Capacitor
-40° to +85°C. I know the temperature is never going to be an issue
(CPU is toast at ~70°C), but what about the voltage? Can I substitute
a 35V cap for a 6.3V?

And what about tolerances? Any worries there?

Thanks for your help.

Ben

 

[Russell Powell]

With capacitors, one cannot replace on looks alone! The
replacement cap you mention should work with no problems.
Be sure to connect with correct polarization......


--
sincerely,

Russell Powell

Artisan Components
SR. FAE - U.S. Central
[email protected]
469-438-6589

 

[CFoley1064]

As I was wrestling with a half-inch water cooling hose, I broke off a

capacitor on my brand-new (never-powered-on) MSI motherboard. The cap
says 1000µF, 6.3v 105C. Radio Shack has a similar looking cap with the
following specs: 1000µF 35V 20% Radial-lead Electrolytic Capacitor
-40° to +85°C. I know the temperature is never going to be an issue
(CPU is toast at ~70°C), but what about the voltage? Can I substitute
a 35V cap for a 6.3V?

And what about tolerances? Any worries there?

Thanks for your help.

Ben

You're headed in the right direction, but the RS cap is probably a mistake.
Most large electrolytics are made for line frequency rectified power supply
filtering, where the main frequency of interest is 100/120 Hz. Your cap is a
charge storage device for fast demand pulses of current on the motherboard, and
as such, you want to find an electrolytic with low ESR (equivalent series
resistance) at high frequencies. One good choice would be the Panasonic FC
series EEU-FC0J102, (1000 uF, 6.3V) available from DigiKey for 0.76 USD in
single quantities. By the way, watch for polarity -- try to put the - side of
the cap in on the - side of the circuit. You're right -- tolerance and
temperature shouldn't make any difference.

Good luck with your motherboard -- a little patience and you can get the right
part, which might save you from intermittent problems caused by voltage sag on
that part of the board.

Chris

 

[Ben Morehead]

Thanks very much for your help here.

Rgds,
Ben

 

[Ian Stirling]

Thanks very much for your help here.

<snip quoted message incorrectly placed at bottom>

Also, temperature is important.
Caps are typically rated at 1000 hours at the service temp.
Life (very, very roughly) doubles for every 10C you'r below this.
A 65C cap (with 10C internal self heating) in a 35C enviroment will be
at 45C, and will last around 4000 hours. (6 months 24*7)
A 85C cap will last several years.