Replace tantalum capacitor on old graphics card with right type - Page 1
Forum section: electronics / repair

author: ChrisB
author_rank: Newbie
timestamp: May 16, 2019, 09:08:37 am
content: Hello everyone!First of all let me tell you, I still see myself as a beginner in electronics. I have done some soldering but nothing fancy.One of my hobbies is restoring old computers (mostly IBM compatibles from the early 90s) to working condition mainly for retro gaming.Recently I came across an old ISA graphics card that had a broken tantalum capacitor on it. Luckily I spotted the damage before trying it out (see attachment).The writing on the capacitor says: "10 16 F" and I have done some research and I believe it's a 10µF 16V one and the F supposedly stands for it's tolerance (+/- 1%), at least according to this source:https://www.dummies.com/programming/electronics/how-batteries-work/Now I have tried to source a replacement part from Mouser and Farnell (also tried Conrad and Reichelt-Elektronik here in Germany) but wasn't able to find a tantalum capacitor with said tolerance. Best I could find was +/- 5%.I have a few questions obviously:1. Is my interpretation of markings (esp. the "F") correct?2. If yes, why doesn't anyone make these anymore?3. Can I use another type of capacitor as a replacement and would it make sense to replace all the capacitors on the card while I'm at it? (There are a couple of others of same and different type, all tantalum).ThanksChris

author: CJay
author_rank: Super Contributor
timestamp: May 16, 2019, 09:22:09 am
content: Tantalum 10uF, 16V, you're correct.Still manufactured and available (higher voltage rating selected, it makes no differenece if the voltage rating is higher as long as the part physically fits:https://www.conrad.com/p/tantalum-capacitor-tht-25-mm-10-f-25-v-20-w-x-h-55-mm-x-14-mm-tancap-ca42-106m025ab-1-pcs-1578744Personally, Tantalum capacitors are nasty, they fail short circuit and can burn up causing a lot of damage to the board, if it had done that I'd replace the lot but that one is phyical damage, it's been knocked off the board, not burned up so I might just replace that one and ignore the rest.

author: ChrisB
author_rank: Newbie
timestamp: May 16, 2019, 09:44:03 am
content: Hey CJay and thanks for your reply and clarify the thing about the voltage.I have seen a lot of comparable parts, but what about the tolerance?The one you posted is +/- 20% and the "F" on my one supposedly means +/- 1% which is much lower.Doesn't tolerance matter also?ThanksChris

author: CJay
author_rank: Super Contributor
timestamp: May 16, 2019, 09:52:52 am
content: I doubt it will make any difference but you could post a larger pic of the board so we can try and work out what the part is being used for?

author: wilfred
author_rank: Super Contributor
timestamp: May 16, 2019, 10:28:15 am
content: Quote from: CJay on May 16, 2019, 09:52:52 amThe other side of the board in that corner might be more helpful. It doesn't seem to connect to anything on the side shown.

author: ChrisB
author_rank: Newbie
timestamp: May 16, 2019, 10:31:39 am
content: Sounds good, I'll upload some pics when I get home later.

author: David Hess
author_rank: Super Contributor
timestamp: May 16, 2019, 02:48:37 pm
content: I do not know what the F marking means but the part is not 1%. Practically any 10 microfarad 16 volt or higher voltage solid tantalum capacitor will work. A 100 microfarad aluminum electrolytic will also work if that is all you have.

author: ChrisB
author_rank: Newbie
timestamp: May 16, 2019, 05:19:51 pm
content: Here are the pics...Would be interesting to know what the capacitor is for.I removed the capacitor a few days ago. (The image in my first post was an old one.). The capacitor is labeled C36.EDIT: According to thepinoutI deduct that it just connects +5V and GND. If this is correct, why?

author: helius
author_rank: Super Contributor
timestamp: May 16, 2019, 05:35:41 pm
content: Quote from: ChrisB on May 16, 2019, 05:19:51 pmCapacitors are most often used this way: this is called a power supply bypass capacitor, or a decoupling capacitor. It provides a reservoir of charge that can be supplied in short bursts to the components on the board (silicon chips) with less sag than if they had to draw the current bursts from the motherboard. It also absorbs transient noise produced by those chips so the noise doesn't disturb other devices in the computer. You will find that most assemblies are supplied with more bypass caps than are strictly necessary and one or two being removed may still allow them to function normally.

author: CJay
author_rank: Super Contributor
timestamp: May 16, 2019, 06:48:21 pm
content: Quote from: helius on May 16, 2019, 05:35:41 pmHelius nailed it.Those tantalums I specced would be absolutely fine.

author: ChrisB
author_rank: Newbie
timestamp: May 17, 2019, 08:33:40 am
content: Ok, thanks everybody!So would it be advisable to replace all tantalum caps with aluminum electrolytic capacitors while I'm at it?Since the card is probably close to 30 years old, maybe the tantalum ones are bad / out of spec?

author: CJay
author_rank: Super Contributor
timestamp: May 17, 2019, 09:39:18 am
content: You're beginning to over think this.If I was doing it and given that the cost of shipping is the same for 10 capacitors as it is for one, then I'd replace the lot, I wouldn't bother swapping them for aluminium electrolytics as the tantalum ones are easily available and we know they physicall fit and work in there as they're what's already fitted.

author: Bashstreet
author_rank: Frequent Contributor
timestamp: May 17, 2019, 09:55:26 am
content: Quote from: ChrisB on May 17, 2019, 08:33:40 amWell tantalums have good and bad sides.Tantalums have great ESR (High frequency) and stability characteristics compared to aluminum electrolytic'sDepending of application a tantalum will be superior to electrolytic that is why they are used in certain applications.Now there is downside if they go bad they go with a bang... and short they are weak against over current and will pop from surge currents.Still i would replace the tantalum with new GOOD quality higher voltage one and it should do very well.

author: ChrisB
author_rank: Newbie
timestamp: May 17, 2019, 11:54:53 am
content: Thanks for all your input.One last question:Why is it then that with new PC hardware like addon or graphics cards tantalum capacitors are very seldomly used anymore as opposed to aluminum ones?

author: CJay
author_rank: Super Contributor
timestamp: May 17, 2019, 12:20:34 pm
content: Maximum capacitance offered by aluminium capacitors is, I think, much higher than tantalum capacitors and it offers that higher capacitance in smaller physical size packages.

author: cvanc
author_rank: Frequent Contributor
timestamp: May 17, 2019, 12:24:20 pm
content: Quote from: ChrisB on May 17, 2019, 11:54:53 amThey're still there, they just look different. Like almost all electronics parts these days they are surface mount.

author: ChrisB
author_rank: Newbie
timestamp: May 17, 2019, 12:34:27 pm
content: Okay, interesting. But one mystery remains: What does the F stand for?

author: Dacke
author_rank: Regular Contributor
timestamp: May 17, 2019, 02:15:34 pm
content: Quote from: ChrisB on May 17, 2019, 11:54:53 amJust in case you wanted a visual aid of what tantalums look like on modern cards see attached-

author: ChrisB
author_rank: Newbie
timestamp: May 17, 2019, 05:22:44 pm
content: Thanks, what about the F, though? :-)

author: CJay
author_rank: Super Contributor
timestamp: May 17, 2019, 06:10:47 pm
content: No idea, different manufacturers assign different markings with different meanings to their products so unless you can identify the manufacturer there may be no way to find out.

author: Kwakerman
author_rank: Regular Contributor
timestamp: May 18, 2019, 06:34:58 am
content: If the cap is just over the power rails then I don't see why it would need to be 1% tol. That type of tolerance would be for timing circuits rather than power rails. 10 / 20 % should be fine. If you are just starting out in repairs and want to change them all replace the broken one and test it, if it works replace the next and test again and carry on like that. That way you will know where a fault is if something goes wrong

author: james_s
author_rank: Super Contributor
timestamp: May 18, 2019, 07:02:44 am
content: The card will probably work just fine without the capacitor, it certainly won't damage anything to try it. I would just add a new one to my digikey or arrow cart and just get it when I needed enough other stuff to make putting in an order worthwhile.

author: ChrisB
author_rank: Newbie
timestamp: May 19, 2019, 03:21:51 pm
content: Ok thanks everybody for their input! I guess I will replace the cap when I get around to it and probably order a bunch of others and replace all of them in one go.

author: Bashstreet
author_rank: Frequent Contributor
timestamp: May 19, 2019, 03:43:18 pm
content: Quote from: ChrisB on May 19, 2019, 03:21:51 pmThere is not much point change them all as Tantalum's do not age as such (compared to electrolytic's) Just get the one you need.This limits risk of lifting traces and other damage you may do especially if your new on soldering.Old motto works here "If it is not broken do not fix it" best replace only components that are suspect or known to fail (Some old electrolytic's, rifa caps etc)Of course up to you.Cheers.

author: CJay
author_rank: Super Contributor
timestamp: May 20, 2019, 08:37:50 am
content: Quote from: Bashstreet on May 19, 2019, 03:43:18 pmDisagree, if there's a tantalum that's burned up then it's a *really* good idea to swap them all, if it's just broken off the board then it's a choice, personally if I had the iron out and half a dozen tantalums to hand, yeah, I'd do it but there's probably no real need to.

author: Bashstreet
author_rank: Frequent Contributor
timestamp: May 20, 2019, 12:24:30 pm
content: Quote from: CJay on May 20, 2019, 08:37:50 amSure but it is irrelevant on his case where the tantalum been knocked physically and was broken as result.

author: CJay
author_rank: Super Contributor
timestamp: May 20, 2019, 12:41:45 pm
content: Hence the reason I said "if it's just broken off the board then it's a choice".And also the reason I said "I'd do it but there's probably no real need to."

author: Bashstreet
author_rank: Frequent Contributor
timestamp: May 20, 2019, 02:10:21 pm
content: Quote from: CJay on May 20, 2019, 12:41:45 pmNo worries i get lot of people who "disagree" with me. Usually about what burger is best not so often about technical details.

author: james_s
author_rank: Super Contributor
timestamp: May 20, 2019, 09:43:02 pm
content: I don't see any conflict here. Obviously the broken one needs to be changed, but I would not mess with the others. Replacing a part risks damage to the PCB, I do not know the skill level of the OP but over the years I've seen a lot of repairable equipment damaged or written off by ham fisted repair attempts.

author: Bashstreet
author_rank: Frequent Contributor
timestamp: May 22, 2019, 11:29:57 am
content: Quote from: james_s on May 20, 2019, 09:43:02 pmYeah kind of my point with the "Do not mess with it unless it is broken" after myself messingup things over the years by being perfection freak i try help "new players" avoid such mistakes.How good one is there is always risk of damage to the boards and he did say he is relatively inexperienced (OP) might not have best equipment etcI also got the impression he was quite fond of this card and wishes to add it to his collection of vintage equipment as working specimen, so maybe just fix what needs fixing unless he is purely experimenting.I do not claim to be any level of expert or professional, just a hobbyist and maybe this is sometimes good as a person who has experience of decades with the most advanced equipment thousands upon thousands of hours of sucking up solder and replacing components might sometimes forget limitations of others.