Capacitor question?? - Page 1
Forum section: electronics / beginners

author: wadmancpu
author_rank: Contributor
timestamp: September 06, 2018, 07:07:39 pm
content: When choosing a replacement capacitors I have found caps that match capacity, voltage, ect but are sometimes physically smaller or larger. My question is: is there any other factors regarding physical size to consider other than fitting the board or if all the specs are the same can a physically smaller or larger cap be used? Thanks.

author: stmdude
author_rank: Frequent Contributor
timestamp: September 06, 2018, 07:21:41 pm
content: Pitch would be the most important physical factor. Pitch is the distance between the legs of the component.

author: ebclr
author_rank: Super Contributor
timestamp: September 06, 2018, 07:24:54 pm
content: Capacitors must be chosen according to the application, same capacitance and same voltage means very little, Have a lot of another points that needs to be evaluated, Capacitors are more complex than womans

author: wadmancpu
author_rank: Contributor
timestamp: September 07, 2018, 04:03:15 am
content: Yes, I understand your point about pitch. Maybe I should reword my question. Does the physical size of a cap make any difference in performance or function all other things being equal? I understand there's a lot to this stuff but as far as swapping a cap on a board if everything but the physical size were the same, and it fit on the board, will a different physical have any impact?

author: Kirkhaan
author_rank: Frequent Contributor
timestamp: September 07, 2018, 04:18:08 am
content: I would be a little supprised if everything is the same at smaller size.What about the rated ripple current and basic lifetime for example?

author: cvanc
author_rank: Frequent Contributor
timestamp: September 07, 2018, 04:28:49 am
content: I run into this a lot when repairing older gear. Modern electrolytics (um, we ARE talking about electrolytics here, right?) are much smaller than ones from decades ago given the same ratings. Often buying "identical ratings" to your failed part will cause a fit problem because it's just too small to elegantly fit the board well and stand up properly.I find a good approach is to stick with the uF value of the original part and search the catalog by increasing voltage rating until the lead spacing fits my board. Then I have to verify the diameter and height are OK for me. It works for me, anyway. Good luck with your project.

author: 6PTsocket
author_rank: Regular Contributor
timestamp: September 07, 2018, 05:00:21 am
content: It depends on the application. In high frequency circuits a Low ESR capacitor is called for. High temp circuits need caps that can handle it. In many cases like filtering AC, equal or higher capacity and voltage will work fine. If you can make the new cap fit it will often work fine. As pointed out, newer designs are often smaller.Sent from my SM-G900V using Tapatalk

author: Raj
author_rank: Frequent Contributor
timestamp: September 07, 2018, 04:41:50 pm
content: The technology,max temperature,esr,esl and lifespan would be different for different package size.It's like going into a rabbit hole. you'll have to read each model's datasheet to know how each will behave.

author: David Hess
author_rank: Super Contributor
timestamp: September 07, 2018, 05:42:30 pm
content: Ripple current rating depends on both ESR and surface area available to dissipate heat so physically smaller capacitors with the same capacitance, voltage, operating life, and ESR may not be suitable in high ripple current applications because they will operate at a higher temperature due to a higher thermal resistance to ambient shortening operating life.The solution is often to use a replacement capacitor with a larger voltage rating to get a large physical size but in many cases, a larger capacitance can be used as well.

author: wadmancpu
author_rank: Contributor
timestamp: September 08, 2018, 02:31:31 am
content: Exactly what I was looking for, thanks!