Suitable capacitor for Commodore 64 - Page 1
Forum section: electronics / general

author: [Chrille]
author_rank: Contributor
timestamp: February 11, 2021, 07:03:59 am
content: Hi!Is this axial capacitor OK to use for a Commodore 64?https://www.mouser.se/ProductDetail/EPCOS-TDK/B40600B7108M001/?qs=sGAEpiMZZMvwFf0viD3Y3a3yb5D6sPUgaf3u7YhGYUKito78xd6GJw%3D%3DIt is an "Aluminium Organic Polymer Capacitor" instead of the aluminium electrolytic capacitor type that is used originally.It is a 1000 uF 35V capacitor. I know the voltage spec is way more than needed since they originally used a 16V 1000 uF capacitor. I think it would work but do you see a reason why I should not use this capacitor? The reason I want it is because it looks really cool. I want a high quality capacitor that looks cool and work great with the C64.

author: TomS_
author_rank: Frequent Contributor
timestamp: February 11, 2021, 11:06:13 am
content: It seems like it should be fine, "low ESR" of about 5 mili ohm, I dont see any reason why it wouldnt work.Polymer caps, unlike standard electrolytics, probably wont bulge and burst or leak over time since they do not use an electrolyte that can off-gas, so you typically wont see them with any form of "vent" (cross) pattern pressed into the case.Im sure people have used a lot worse caps in their retro electronics when recapping.Also, I wouldnt necessarily buy something based on looks from the retailer. It could be "marketing" or it could even be a picture of another series. You might be disappointed if it arrives with a blue or black or some other colour wrapping.

author: [Chrille]
author_rank: Contributor
timestamp: February 11, 2021, 03:14:02 pm
content: Quote from: TomS_ on February 11, 2021, 11:06:13 amThanks for your answer!Of course you should not buy something based only on looks. I know what you mean. But in this case I was mostly interested in the component capability, performance and compatibility with the C64 since I don't want to risk to damage the computer because I would use another type of cap than the one used originally by Commodore.The specs of this cap looks great what I can tell. I am however not an electronics guru that is why I want to ask you guys before I make the purchase and buy the wrong parts. In this case I am fairly certain that they actually have the nice orange wrapping and I think it would look good. I want to buy new caps that are better than the ones originally used and if it is possible to enhance the looks of the mainboard then why not?

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 11, 2021, 03:32:44 pm
content: Quote from: TomS_ on February 11, 2021, 11:06:13 amWhereas the above cap is probably more robust than your typical electrolytic cap, the ultra low ESR may actually be a problem.It's easily 100 times lower than the typical ESR of classic electrolytic caps of the same capacitance.I don't know where this cap is located on the Commodore 64, but if it's at the output of some linear regulator, a very low ESR may actually cause stability issues.

author: TomS_
author_rank: Frequent Contributor
timestamp: February 11, 2021, 07:54:33 pm
content: It is most likely either on the output or input to a voltage regulator. Theres maybe 3 (IIRC) big caps around the power supply.

author: rsjsouza
author_rank: Super Contributor
timestamp: February 11, 2021, 08:37:38 pm
content: Although the Aluminium Poly capacitor is extremely overkill for a linear regulator, I don't really see an issue in using it. It boasts a 4000h endurance at its peak temperature (125C), but there are other regular Aluminium capacitors (here) with much more endurance (I don't think you will use it all up, though).According to aschematic that I found on the web, there are a few 1000uF capacitors on the C64, all around linear regulators (7812 and 7805). Given that any of these voltage regulators' datasheets (one examplehere) only recommend putting much lower values of capacitors around them, I suspect that either their influence will be small or not important for the circuit. .

author: [Chrille]
author_rank: Contributor
timestamp: February 11, 2021, 09:20:27 pm
content: Quote from: rsjsouza on February 11, 2021, 08:37:38 pmThe board I am using is a 250469 board and here is the schematics for it:http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/250469-rev.A-right.gif

author: rsjsouza
author_rank: Super Contributor
timestamp: February 11, 2021, 10:40:42 pm
content: Ok, if it is C63 then anything goes there.

author: [Chrille]
author_rank: Contributor
timestamp: February 13, 2021, 08:25:17 pm
content: Ok thanks!So it seems it would be OK to use the EPCOS capacitor.I have found another capacitor too that also looks promising:https://www.mouser.se/datasheet/2/427/120atc-1761999.pdfThat is a 16V 1000 uF aluminium electrolytic capacitor which is the type used originally if I am not mistaken. According to the data sheet it is an automotive grade capacitor. I guess it means it should have a greater life expectancy than regular general purpose caps.What do guys think? Is it a good choice for my C64?And another question regarding ripple current. Is it always better to have a high ripple current vs low? Does this matter in this application?

author: james_s
author_rank: Super Contributor
timestamp: February 13, 2021, 10:42:42 pm
content: Automotive normally means it has a wider temperature range that it can tolerate.This is really not critical, don't over-think it. Select a capacitor from a reputable manufacture in the correct value and it will work. The linear power supply used in the C64 does not require anything special in the way of capacitors.

author: rsjsouza
author_rank: Super Contributor
timestamp: February 13, 2021, 11:31:32 pm
content: As james_s mentioned, automotive grade capacitors will have good endurance over its temperature range and will be more vigorously tested when compared to commercial variants.Since you are buying just one, go for it. It is rated for 8000h, which is very respectable, and it has a good characteristics overall.

author: floobydust
author_rank: Super Contributor
timestamp: February 14, 2021, 03:33:57 am
content: Note that C63 1,000uF 16V is low cost and a bit small in value. Typically, to prevent crashes and reboots due to mains flicker, 2,200uF or more is used. Schematic says "France Version: C63 2,200uF Required". It is larger value in later C64's I believe.I would not bother with high cost solid-polymer as ESR is not important here, unlike an SMPS.Voltage-doubler capacitor C45 220uF experiences high stress due to the ripple current, so I would replace it as well.

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 15, 2021, 03:11:53 pm
content: Quote from: floobydust on February 14, 2021, 03:33:57 amAs it's the filtering right after the rectifying bridge, the only reason I see for this difference would be mains frequency, which is 50Hz in France and 60Hz in the US.A lower freq will require more capacitance indeed. Probably not as much as twice though, but you're right, it won't hurt to use a 2200uF cap for the US version as well.Where is the 5V regulation on the schematic? I may have missed it, or the linked schematic may be incomplete?

author: [Chrille]
author_rank: Contributor
timestamp: February 15, 2021, 06:10:14 pm
content: Isn't a 2.2x increase of capacitance too much? I mean most 250469 boards did come equipped with a 1000uF capacitor. Is this only because Commodore were cheap and didn't want to spend to much on caps? Not that there is a big difference in priceI have a Swedish/European version and as far as I know all European countries use 220-240V 50Hz. Why would France use a different version than the rest of Europe?There is a smaller capacitor on the board that is a 2uF 50V cap. It seems to be really hard to get caps with that capacitance value. I guess it doesn't hurt to go with a 2.2uF instead (no risks)? It's only a 10% increase.

author: rsjsouza
author_rank: Super Contributor
timestamp: February 17, 2021, 12:00:46 am
content: Quote from:  on February 15, 2021, 06:10:14 pmNot where the capacitor is located. The different is not very large.Quote from:  on February 15, 2021, 06:10:14 pmProbably so. Commodore and *cheap* were synonyms. Jack Tramiel's motto was "computer for the masses not the classes". Also, a small difference in price is huge when mass producing anything - more so at the time this computer was manufacturedQuote from:  on February 15, 2021, 06:10:14 pmA citation on a schematic was probably for internal use and therefore it may have been a generalization to "Europe" or "Western Europe" as a whole.Quote from:  on February 15, 2021, 06:10:14 pmNo risk at all. Capacitors usually have a very wide tolerance and, at the time of this computer's manufacturing, tolerances of -20%/+80% were very common.

author: floobydust
author_rank: Super Contributor
timestamp: February 17, 2021, 09:17:37 pm
content: It looks like the power pack outputs 9VAC 1A and main +5.3VDC 1.5A from Sanken 3052P IC and 4,700uF filter cap. Tons of wrong schematics and just dumb info on the C64 power packs.Later C64's upsized the capacitors so that's why I felt they are on the small side:#2523129VAC, C63 is 1,000uF 16V feed to 5V shunt reg.5VDC C58 100uF 16VVoltage-doubler C45 220uF, C66 330uF 35V feed to discrete 12V or 9.6V reg for SID.#2511389VAC, C19 is 2,200uF 16V feed to 7805.5VDC C91 100uF 16VVoltage-doubler C90 470uF 50V, C88 470uF 50V feed to 7812.#251469, #252278, #3261069VAC, C19 is 2,200uF 16V feed to 7805.5VDC C91 100uF 16VVoltage-doubler C88 1,000uF 25V, C90 470uF 25V feed to 7812.http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/index.html

author: [Chrille]
author_rank: Contributor
timestamp: February 22, 2021, 09:10:00 pm
content: Ok, now I am about to order a full set of capacitors for my C64.I have decided to go with Nichicon UVR-series for all caps except the axial 1000uF capacitor since no axial Nichicon 1000uF caps are available from Mouser. The Nichicon UVR looks like a good choice for computers/home electronics use. Anyone here with experience using those caps? Are they any good?I noticed that if I choose a capacitor that has a higher max voltage with the same capacitance value the ripple current value gets higher. Is there an issue with using capacitors with too high ripple current value? Performance issues or risk of damage to sensitive components like IC:s etc?This is the complete list of capacitors used on the board I have:2uF 50V4.7uF 25V10uF 25V47uF 16V100uF 16V220uF 16V220uF 25V470uF 35V1000uF 16V (axial)Would it be OK to use 50V variants of all these capacitors? The axial 1000uF capacitor will probably be a 25V 1000uF one from Vishay. As you can see from the list of original caps one of them (2uF) is already a 50V cap and the 470uF is a 35V cap.Here is a data sheet for one of the capacitors from Nichicon UVR-series:https://www.mouser.se/datasheet/2/293/e_uvr-1889929.pdf

author: floobydust
author_rank: Super Contributor
timestamp: February 23, 2021, 08:19:47 pm
content: Yes, going higher voltage is OK and you almost need to because their size is comparable to the big originals. Modern parts are so much smaller.Part of the ripple current spec is heat dissipation so a larger (voltage) part can take higher ripple current, and higher rating (ripple current) is better.But the C64 isn't really stressing them much aside from the 220uF voltage-doubler cap sees high ripple current. Note when comparing capacitors there is a wide variance in their ripple current spec, so I would avoid low end i.e. 350mA compared to 740mA parts.UVR is fine, consumer grade, 2,000hrs@85°C. I useUPM5,000hrs@105°C orUPWfor smaller. Nichicon is still a top brand for electrolytics.Using radials for an axial replacement, I'll bend one lead up and tack glue the cap to the board with a blob of silicone. It's not pretty, and sometimes I just run a wire alongside the radial cap. Don't hard bend the cap's leads to stress the rubber bung, use pliers to bend them a bit away from the body.

author: bostonman
author_rank: Super Contributor
timestamp: March 17, 2022, 03:36:09 am
content: Sorry for the late response, but I just came across this.As a reference, I took scope measurements and there is a discussion about capacitor replacement.https://www.lemon64.com/forum/viewtopic.php?t=79320

author: free_electron
author_rank: Super Contributor
timestamp: March 17, 2022, 04:25:51 pm
content: small side note : "Low ESR" is not always good . the inrush current can be very high. Some regulators needs a bit of esr ( 1 to 2 ohms ) to keep the loop stable. If you are working with higher voltages ESR doesn't really matter provided you have margin before the regulator.Let's say you have 15 volt feeding a 7805. The peak current the regulator can handle is 1.5 ampere. and it needs about 8 volts to work properly. so you have 15-8 = 7 volts of headroom. at 1.5 ampere means you can get away with almost 5 ohms of ESR on the capacitor. It will still work.Now. if you have a 5 volt rail and make 3.3 volts out of it... there is only 1.5 to 1.3 volt headroom (LDO dropout of 0.2 to 0.4 volt. The new mos based ldo's can really go to zero drop). Pull 1.5 amp and 1 ohm is a problem.The reverse is also true. typical MLCC ( chip ceramic) capacitor . 10 uf. you apply 5 volts from a very low impedance source ( like a switching power supply found in a desktop computer ). the peak current in that small cap can be as high as 16 ampere. I've seen bondwires literally explode in regulators because the esr was too low. Many regulators these days use a so called soft-start feature. They severely limit the current until the output capacitors reach at least 1/3 of the output voltage. Then they go full throttle. Some of the smarter regulators even have a power good or reset output. the idea is to keep the system in reset until all caps are charged. As long as a processor or fpga is in reset it doesn't consume anything . consumption happens when the clock starts running. in steady state cmos systems only consume leakage current.So you will see that in complex systems with many power rails they use such setups.