Diodes and Rectifiers and NES Consoles Oh My! - Page 1
Forum section: electronics / beginners

author: TheSwartz
author_rank: Newbie
timestamp: July 14, 2021, 10:18:04 am
content: Sorry, newb questions. I've been learning a lot, but this is something I can't seem to figure out on my own. And I apologize, I am not sure I have some of the proper terminology figured out regarding the diode rectifier I'll be referring to.I took apart an NES console, replaced all the capacitors and doing other maintenance. I have read that the diodes in the power supply goes bad sometimes, and I think it was implied that this can be replaced as part of the preventative maintenance. (of note, I tested all 4 diodes, and they are OK in the proper directions per my multimeter). Besides, it gives me something else to learn too!Of note, the power supply is a complete pain in the butt to take apart, so I'd like to do everything I need to do now and never have to do this again! (famous last words...)In short, there are two NES versions, one uses 4 discrete diodes, the other uses a diode bridge rectifier. I have the model with the 4 discrete diodes. I am attaching a photo. From what I can see, there does not appear to be any writing or numbers to identify them either..What I need to know is, what diodes replaces these? I have reviewed the schematics that helped me replace the capacitors, internet searched, watched videos, and direct messaged a couple you tubers who do console repairs (no replies LOL) and I can't seem to figure this out. I barely have a handle yet on the different types and specs for diodes -- I just want to know what to purchase for now and I'll keep learning about these. Any ideas?Thanks!

author: pqass
author_rank: Super Contributor
timestamp: July 14, 2021, 11:35:05 am
content: They look like glass small signal diodes being used in rectifier service; probably 1N4148 or 1N914 would do.Standard 1N4001 diodes in a plastic package probably won't fit.But why would you suspect they go bad? The circuit it's powering (an RF modulator?) doesn't look demanding (large current draw).Quote from: TheSwartz on July 14, 2021, 10:18:04 amMaybe you're looking at the wrong diodes? That isn't the main power supply.I stand corrected. They are the main rectifier diodes!See attached.

author: wraper
author_rank: Unknown
timestamp: July 14, 2021, 11:54:13 am
content: Quote from: pqass on July 14, 2021, 11:35:05 amThey are not as small as you think and using 1N4148 will cause a failure. 1N4001 - 1N4007 should be fine. Rectifier used in another version mentioned is RC203 (200V 2A).QuoteThey power the rest of the console as well.

author: bobbydazzler
author_rank: Regular Contributor
timestamp: July 14, 2021, 12:59:46 pm
content: My guess would be 1N400x would be fine to replace them with, but I'd like to see the datasheet/basic specs of the original diodes. Surely that information is out there somewhere?

author: MathWizard
author_rank: Super Contributor
timestamp: July 14, 2021, 03:43:44 pm
content: So OP do you mean an original N.E.S. ?Looks like some video input/output UVF/VHF type circuitry. Although I see what looks like a barrel jack input and that big cap, those look like little small signal diodes, way closer to 1n4148 than a 1n4001 rectifier.So is that a barrel jack, what voltage is applied to the bridge rectifier? Surely that can't be the main input power jack. Whatever it is, it's probably pretty low power.But OK people above are saying it is the main power rectifierI can't remember NES very good, never owned 1.

author: mariush
author_rank: Super Contributor
timestamp: July 14, 2021, 04:11:42 pm
content: A quick google search reveals that the power adapter is most like 9v AC 1.3A :https://www.reddit.com/r/nes/comments/2jllse/anyone_know_what_ac_adapter_can_substitute_for_a/Basically the adapter just has a regular classic linear transformer inside it.So the bridge rectifier has to rectify 9v AC to around 9v x 1.414 - 2 x voltage drop on diode .. so a DC voltage with peaks up to around 11v. The capacitor will smooth the output enough so that the 7805 linear regulator or whatever it used will get the minimum of around 6.5-7v it needs to regulate properly.The current is not a big deal... I'd bet the console doesn't even hit 1A of current but even so, two diodes are always conducting so the current is spread across both diodes.I wouldn't have replaced the diodes ... now replace them with whatever you have on hand .. 1n400x, 1n581x , basically anything that can handle 20-25v and 1A of current or more.If you feel adventurous, you could get a bridge rectifier and spread its 4 pins/legs to fit them in the right holes and you can replace the 4 diodes.

author: TheSwartz
author_rank: Newbie
timestamp: July 15, 2021, 06:35:12 am
content: Quote from: pqass on July 14, 2021, 11:35:05 amTo be honest. I don't know if they do. I'm starting to think that since I'm not finding much information maybe they don't? There was one 1990's video (someone uploaded the VHS tape to YouTube) that was an instructional video for people servicing Nintendos at the time and it mentioned a "top 4 things" to look for if things go bad on an Nintendo, and this was one of them. And, I'm looking for things to practice desoldering / soldering, and things to figure out so I learn how this works, so I thought I'd give this a go too!Quote from: pqass on July 14, 2021, 11:35:05 amYep, this is it!Quote from: wraper on July 14, 2021, 11:54:13 amOKQuote from: wraper on July 14, 2021, 11:54:13 amThis is my understanding, yes.Quote from: bobbydazzler on July 14, 2021, 12:59:46 pm1N400x is also suggested above. I have been looking, I think I might not be experienced enough to know search terms, etc. to find this sort of thing?Quote from: MathWizard on July 14, 2021, 03:43:44 pmYes, The Nintendo Entertainment System! Sorry, I assume other people know what I'm thinking sometimesYes it's a barrel jack. On a sticker on the bottom of the NES, it says 9V 850 mA. I don't have my original power supply anymore. All the replacements I've seen are 9V but like 1A or 1.2 or 1.3A..Quote from: mariush on July 14, 2021, 04:11:42 pmYep, I don't have an original power supply anymore, but 9V 1.3A is what two third party supplies I have. FYI, what's listed on the console is 9V 850 mA.Quote from: mariush on July 14, 2021, 04:11:42 pmOK. Of note, I have NOT taken these out. I had intended to replace them as a preventative maintenance issue and as something to do more practice/learning with, but it seems I'm getting the advice "if it ain't broke, don't fix it"?BTW, yes the regulator I replaced is a 7805 5V regulator.I did wonder about replacing with a bridge rectifier, but figure I don't know enough to figure that out yet. Good to know it's a possible option! ThanksThank you for showing some math. I will study that to learn about this more.Seems a consensus is with "1n400x" diodes. There is a supplier that sells parts for retro video game consoles (where I have got a lot of info from). Of the various diodes they sell,one is the 1N4005. I suspect this is probably sold for this reason.THANKS!!

author: BrokenYugo
author_rank: Super Contributor
timestamp: July 15, 2021, 07:35:04 am
content: I wouldn't worry about the diodes, plenty of originals running fine, but 1N4007 (because why not use 1kv parts) will certainly work if they fit, mind the polarity.The part you really want to focus on in the RF box is that little 100uf cap right next to the big one by the regulator on the 5 volt rail. That's the first to fail (from heat) and when it does the regulator oscillates and causes weird video distortion. Use 105C temp rating with the highest hour rating you can find that will fit in there. I used a Nichicon ULD1E101MED1TD.

author: mariush
author_rank: Super Contributor
timestamp: July 15, 2021, 03:34:20 pm
content: Quote from: TheSwartz on July 15, 2021, 06:35:12 amThe benefits of using a bridge rectifier is the higher surface area to dissipate heat while with individual diodes the diodes themselves will dissipate most heat and the leads will also push some heat into the circuit board.1n400x diodes are recommended because they're generic, common, easy to find. The last digit is just the maximum voltage the diodes are rated for. You could go for 1n4007 for example, but do you really need 1000v if the circuit sees maybe 20v peaks?1n581x (1n5817, 1n5818, 1n5819) is another series, a bit better, with lower voltage drop ... basically again, maximum voltage is the difference between them 20v for 1n5817, 30v for 1n5818, 40v for 1n5819 but the reverse voltage for 1n5817 is a bit low at 14v so I'd use 1n5818 or 1n5819 and avoid 1n5817 for this application.

author: TimFox
author_rank: Super Contributor
timestamp: July 15, 2021, 03:47:10 pm
content: The "1N400x" series of rectifiers is very common.Interesting: at Mouser, for one manufacturer, the 1N4007 (1000 V PIV) is 5% cheaper than the 1N4002 (100 V PIV) in small quantities. For another manufacturer, they are the same price in small quantities.

author: Gyro
author_rank: Super Contributor
timestamp: July 15, 2021, 04:01:25 pm
content: I wonder what bright spark though it would be a good idea to put the input rectifiers in the same can as the video modulator!

author: helius
author_rank: Super Contributor
timestamp: July 15, 2021, 05:39:23 pm
content: Quote from: Gyro on July 15, 2021, 04:01:25 pmEvery cent was squeezed out of these designs where possible. Even something as mundane as saving a pin for ~V if the circuit requiring it is on the same board as the inlet. Of course, they used the awful ZIF cartridge connector that was the cause of so many malfunctions, and expensive besides. But that was required by marketing.Quote from: mariush on July 14, 2021, 04:11:42 pmSurely the two conducting diodes are in series, so current is never "spread across" them?

author: BrokenYugo
author_rank: Super Contributor
timestamp: July 15, 2021, 06:23:07 pm
content: Quote from: mariush on July 15, 2021, 03:34:20 pmI would not recommend using a Schottky here, that will move more losses and heat to the 7805, which is already fed something like 12 volts, not heatsinked all that well, and cooks one of the more critical electrolytic caps in the system.

author: bobbydazzler
author_rank: Regular Contributor
timestamp: July 16, 2021, 02:29:08 am
content: I 2nd "if they aint broke don't fix it". The diodes look chunkier(maybe an optical illusion) than 400x diodes so are most likely rated for higher current than 1amp. They've probably had an easy life supplying the NES with power so much so it looks like the designers even put insulation on the leads(you wouldn't want to do that if you were worried about their temperature).

author: BrokenYugo
author_rank: Super Contributor
timestamp: July 16, 2021, 07:06:16 pm
content: Quote from: bobbydazzler on July 16, 2021, 02:29:08 amThat's a fair point, I've not measured real draw on mine but the adapter being rated for 1.3A and the use of a 2A bridge in other variants may explain the use of glass body power diodes that deep into the 80s over presumably cheaper, bigger, plastic ones that probably wouldn't fit. I just pulled a spare out my parts box and they don't have parts numbers, about the same diameter and maybe a bit shorter than a 1N400X, but glass, so probably rated for higher temp/power.