Choosing replacement electrolytic capacitors.  - Page 1
Forum section: electronics / beginners

author: YoshiKnuuckles
author_rank: Contributor
timestamp: December 16, 2015, 02:24:33 pm
content: I'm going to be working on an NES top loader in a week or two, and I need to replace the capacitors in it. So far I've just used pre-made kits from Console5.com, but I'd like to start ordering parts directly from Mouser or Digikey.The issue I'm having, is there are so many parts to choose from, and it is difficult to tell exactly which capacitors I should order. I already plan to buy quality brand, but I'm having trouble figuring out what caps would work.What are the things I should look for? I know to match the capacitance rating, and to select ones that have an equivalent or higher voltage rating, but then it starts getting into ripple voltage, temperature rating, ESR, size, etc. and my head starts to spin.I guess what I'm asking is, what should I worry about when choosing replacement caps, and what should I ignore? Hopefully this isn't too silly of a question.Thanks in advance for any advice.

author: macboy
author_rank: Super Contributor
timestamp: December 16, 2015, 03:21:14 pm
content: Buy 105ocapacitors unless you absoltely know that 85 is OK (which you don't).Usually, you use the same capacitance (uF / nF / pF) as the originals. Don't second-guess the original engineers on this one.Buy caps with the same or higher voltage rating as the originals. For example, if you are replacing a 100 uF 35 V cap, and you have a 100 uF 50 V one on hand, you can use that. Higher voltage is usually higher cost, so you won't necessarily buy the 50 V one (unless you are buying them in bulk anyway, making them cheaper). Also, higher voltage will be bigger. Maybe taller, maybe fatter, maybe both.Note the size of the originals and buy similar sized replacements. Caps of the same ratings will range from short and fat to tall and skinny, but you need something that will fit. For very small ones, if the leads are not spaced exactly the same, you can just bend them. Bigger ones have thick leads and will often sit too high off the board if you try bending them to fit, so buy replacements with the right lead spacing to begin with.For ESR, if you know the cap is used in a switching power supply (not likely for NES) then choose a low ESR cap designed for switching power supplies. Otherwise, any good brand will do and will likely have lower/better ESR than the originals. I buy Panasonic FC or Nichicon VX as good generic electrolytics.

author: YoshiKnuuckles
author_rank: Contributor
timestamp: December 16, 2015, 03:33:11 pm
content: Thank you macboy, that was exactly the type of advice I was looking for.

author: Mephitus
author_rank: Regular Contributor
timestamp: December 16, 2015, 04:54:12 pm
content: I have serviced numerous legacy systems (NES, genesis, SNES, etc) and found that 85° standard electrolytic caps work just fine for a complete recap. Which I recommend for all NES units that still have original caps, regardless if it works or not. Its pretty rare for a NES case to get hot unless you do some strong overclocking, so using 105° is not exactly required, but doesnt hurt at all. If you want it to last forever, you can use low ESR aluminum polymer capacitors. Though this is also a little overkill (IMHO). Itcan possiblyimprove the video output end, but my personal results have been a mix of either only slightly better or the same performance. (YMMV)If you are going to pop the case, I very highly taking a look/consideration for a few other mods that are pretty useful while you are at it. Some of the better ones can be found here:http://www.raphnet.net/electronique/nes_mod/nes_mod_en.phpSince you said its a top loader, I also strongly recommend modding it for composite output. This can drastically improve its output on modern TV's:http://www.gamesx.com/rgbadd/nes2avmod.htmIf you are interested in overclocking, I recommend a mod that allows you to vary the clock speed using dip switches. You can find a PDF walking you through this process here:http://personales.alumno.upv.es/~jogilmo1/nes/textos/arxius/oc_en.pdfIf you need some additional documentation let me know. I have collected a good amount over the years of servicing them. Even how to repro an entire NES using a single FPGA. (pic attached) Hope to try that one eventually. LULZEDIT: Forgot to mention, the original AC adaptor for the NES is a non-rectified transformer that is then rectified by the NES internal hardware. Haven't had a chance to check the NES2 original adaptor, but wouldn't be surprised if it was the same/similar.

author: YoshiKnuuckles
author_rank: Contributor
timestamp: December 16, 2015, 05:25:44 pm
content: The NES top loader I'm doing is getting an NES RGB mod installed in it. I usually do a full cap replacement on these and test them before I install the NES RGB, as it draws extra power. What I can do to it depends on what my friend(customer) wants done to it.Thanks for the info Mephitus. I'm also trying to spec out a 1.5 amp voltage regulator to replace the 1 amp regulator since the NESRGB draws additional current. Any suggestions on that? I'm currently looking at this TI package:http://www.mouser.com/Search/ProductDetail.aspx?R=UA7805CKCSvirtualkey59500000virtualkey595-UA7805CKCSThanks for the help, I do appreciate it. I'm trying to learn all I can about electronics, although I'm finding it slightly intimidating. So much stuff to take in.

author: wblock
author_rank: Regular Contributor
timestamp: December 16, 2015, 05:50:09 pm
content: Quote from: YoshiKnuuckles on December 16, 2015, 02:24:33 pmLook up the data sheets on the original caps and match those specs with the replacements. ESR and ripple ratings are important. Size matching is necessary, both for height and diameter but also for lead spacing.

author: Mephitus
author_rank: Regular Contributor
timestamp: December 16, 2015, 06:56:45 pm
content: Quote from: YoshiKnuuckles on December 16, 2015, 05:25:44 pmIt's all good. I am still a little new myself. But am just diving into things as best I can. So far as I can tell, the voltage regulator you posted should work just fine. I am at work right now, so I cant pull my NES out to check this one vs the original.