Replacing multiple caps... Don't have matching values...

[Noozer]

Howdy!

I have a board with some failed capacitors. These are 3300uf 6.3v
capacitors. I don't have any 3300uf caps handy, but I do have some other
values and was wondering if a different combination of values could be
substituted. The caps are connected in parallel (all + leads together and
all - leads together) to filter a power bus.

How can I calculate the resulting capacitance of these three parts combined
and then break it into other values. (similar to how you could put two 500K
resistors in series to substitute for a 1000K resistor).

Thanks!

 

[Noozer]

I have a board with some failed capacitors. These are 3300uf 6.3v
capacitors. I don't have any 3300uf caps handy, but I do have some other
values and was wondering if a different combination of values could be
substituted. The caps are connected in parallel (all + leads together and
all - leads together) to filter a power bus.

How can I calculate the resulting capacitance of these three parts
combined
and then break it into other values. (similar to how you could put two
500K
resistors in series to substitute for a 1000K resistor).

DOH.. there are three of these capacitors in parallel.

 

[alpha_uma]

"Noozer" <dontspam@me.here> wrote in message
news:XdjIc.73919$WB5.47145@pd7tw2no...

I have a board with some failed capacitors. These are 3300uf 6.3v
capacitors. I don't have any 3300uf caps handy, but I do have some other
values and was wondering if a different combination of values could be
substituted. The caps are connected in parallel (all + leads together
and
all - leads together) to filter a power bus.

How can I calculate the resulting capacitance of these three parts
combined and then break it into other values. (similar to how you could
put two
500K resistors in series to substitute for a 1000K resistor).

DOH.. there are three of these capacitors in parallel.

This is a late reply, but FWIW.

Cap values are added together if the caps are wired in parallel (in contrast
to resistor values). So, to get close to 3300uF, THEORETICALLY you could
wire two 1000uF caps and one 1500uF cap all in parallel (assuming you have
caps of these other values handy). I think it would be much less of a hassle
to order some 3300uF caps of the right sizes online from DigiKey or Mouser
than try to pack three caps together in the space of one. This would be
quite messy if the original 3300uF caps were already sitting side-by-side to
each other.

Make sure you order the ones with the correct diameter, lead spacing and
maximum rated voltages. It is OK (better, in fact) to order ones with higher
max rated voltages, but "higher rated V" means more money. I'd prefer ones
rated at least 10V, but I could not locate any online store selling 3300uF
electrolytic caps rated higher than 6.3V. For motherboard applications, I
also wouldn't want to use any caps having a max temp rating of less than
105degC. Just watch out that you don't accidentally order ones rated at only
85degC (Ebay has lots of these).

I recently ordered some 3300uF electrolytics (plus some other stuffs to make
up a minimum order of thirty-some C$) from DigiKey, and they were able to
ship them to me (for only 8C$) in less than 1.5 days. [BTW, if you happen to
be in Canada, DigiKey can ship to Canada via Purolator which does not charge
any "hidden" customs brokerage fees or customs handling fees.]

Al-U