Choosing Replacement Capacitors - Page 1
Forum section: electronics / beginners

author: jasenrogers
author_rank: Newbie
timestamp: November 11, 2019, 04:23:39 am
content: Hello all! this is my first post so I hope I don't break any rules. ;-) I am trying to find the data sheets for capacitors out of a power supply in a Macintosh Performa 630CD. They are Nichicon and they say they are 22uf/35v. On the other side they have KMA and 105c. On the top it has 47D3 stamped I think. Anyway, I have been searching on Google but can't seem to find anything about these. I looked on Mouser and the Nichicon website but can't find anything about these caps. I am assuming that they are KMA series. Anyway, if anyone has any ideas where I can look for info on these caps, I would greatly appreciate it! Thanks!

author: helius
author_rank: Super Contributor
timestamp: November 11, 2019, 04:50:03 am
content: KMA is the name of a series from Nippon Chemi-Con (totally different from Nichicon). The full part number would be EKMA350EFC220MF07D or EKMA350EC3220MF07D, depending on how the leads are formed (5mm or 2.5mm Lead-Spacing)There is really no need to exactly match the parts when replacing capacitors: what you need to do is to take down some data like capacitance, working voltage (W.V.), lead spacing, case size, and ESR and do a parametric search using a distributor website like Mouser or Digi-Key, or a cross-site search tool like Octopart or Findchips. Some parametric searches are more accurate or more complete than others, so it pays to double check the results until you get enough experience to trust the one you're using.For capacitors in power supplies, the ESR is frequently an important parameter, since it affects how much heat is generated by continuous charging/discharging. Choosing a low-ESR type is important, and depending on how much room there is, a higher-voltage or larger-case part may have lower ESR. You can use a higher rated voltage part than was originally spec'd, and lower may also be okay: if the rail is regulated to +12V, then a 25V rated cap is just as good as a 35V one. You can use multiple-selection or ranges in the parametric search to find an appropriate part.Getting the right lead spacing is more important than you might think, because it enables you do plug the replacement directly into the PCB holes without having to bend the pins, which might have undesirable side effects (weakened bung seal, short circuits, mechanical problems from mounting higher than flush). In confined spaces like power supplies, the case size is also important (specified as mm of diameter x height, as in 6.3x7).

author: jasenrogers
author_rank: Newbie
timestamp: November 11, 2019, 03:50:01 pm
content: Wow, that is one detailed response!Thanks so much! I feel like such a noob. One of the caps on the board was Nichicon so I never thought to look for a different brand with that series. Thanks so much for the pointers! This is my first foray to this level of repair. Im sure you can't tell!

author: wraper
author_rank: Unknown
timestamp: November 11, 2019, 04:03:44 pm
content: They are just general purpose capacitors. Anything with same or higher voltage rating will be fine.

author: andy3055
author_rank: Super Contributor
timestamp: November 11, 2019, 05:22:46 pm
content: The temperature rating should be taken into account, unless you know for sure it is not critical in this instance. 105 to 85 degree change is quite sizable.