Do I need to use the same exact model and series or can I use any similar capacitor?

[giyad]

Hi,

I recently had a board crap out on me and as I took the case off I noticed some bad capacitors. I want to replace them, but its an old board and I can't find the exact capacitors. I'm able to find caps with the same voltage and uf rating, but not the same series number. I know the diameters as well. The caps are rubycon 16V 1800uf mcz, rubycon 6.3V 2700uf mfz, and samxon 6.3V 1500uf gc (m) voa. I can find the rubycon mcz on amazon, but the others I can't find. So I'm thinking to just go into digikey and choose caps with similar voltage, uf, and diameter for all of them. Is that fine?

Also, when soldering, I'm new to this as well, I notice that my iron doesn't melt the solder to liquid, it melts it and then it falls down into a ball. Is my soldering iron not hot enough? Its a radioshack brand, and I'm using the 40W setting (highest it goes). Ive never tinned my iron because as I try to it just makes the solder fall off into a ball, so it doesn't stick to the iron.

[rhomanski]

Re: Do I need to use the same exact model and series or can I use any similar capacit

Manufacturer and series doesn't matter as far as replacements. It's the type, low noise or low leakage or low ESR and the values that matter. Also use good quality Panasonic, Nichicon, or United Chemi-con, something like that. Epcos or Cornell-Dubillier. Stay far away from Chinese capacitors. If the unit is old it will be hard to find the same diameter without getting a higher voltage. The caps are much smaller than they were 40 years ago. In the eighties they made major improvements to caps.

Your soldering iron tip is unsolderable. You can try filing it down to fresh metal or get a new tip or just take it back and get a new one. Corrosion will cause it to not be solderable. One time I got a bunch of banana jacks out of stock, 130 of them, got them all mounted and then tried to attach wires. They were ruined, had to throw all of them out and get new. If you want, try chucking up your tip in a drill and hold it against a file. Let it spin against the file until your down to new metal, you can put a new tip on it too when it gets thick and dull.

[Per Hansson]

Re: Do I need to use the same exact model and series or can I use any similar capacit

The caps on your board are Ultra low ESR.
Most of the major manufacturers that rhomanski mentioned have unfortunately stopped production of them and switched to solid polymer caps.

Depending on what part of the circuit the failed caps are in it might be advantageous to switch to solid polymer caps instead.

[BustinCaps]

Re: Do I need to use the same exact model and series or can I use any similar capacit

@giyad. I would be cautious about buying capacitors at Amazon or ebay. A lot of fake capacitors being sold out there. Stick to more reputable sites such as Digi-Key or Mouser.

[giyad]

Re: Do I need to use the same exact model and series or can I use any similar capacit

Thanks for all your help!

So I'll definitely be using Digikey or Mouser, but I'm not able to find caps with the same ESR or Ripple. If my ESR is .012 Ohms, but I can't find any, should I go with something lower (like .07 ohms) or higher (.14ohms)?

Same thing for ripple, mine is 2220mA, but I can find only 1950mA or 2880mA.

Also, if I select the same height, I end up only having options for .3ohms

[Stefan Payne]

Re: Do I need to use the same exact model and series or can I use any similar capacit

To be safe, use the value closest to the original specced caps.
So in this case 14 Ohms would be better than the 7 Ohms one.

Still, depending on where you are using them, it may work with lower ESR values as well.

[giyad]

Re: Do I need to use the same exact model and series or can I use any similar capacit

So I've chosen three caps. If someone doesn't mind looking them over and comparing them with the ones I'm replacing I'd appreciate it.

Nichicon UHW replacing Rubycon 16V 1800uf MCZ, 10mm diameter
Nichicon UHV replacing Rubycon 6.3V 2700uf MFZ, 10mm diameter
Nichicon UHV replacing Samxon 6.3V 1500uf GC, 8mm diameter

[Per Hansson]

Re: Do I need to use the same exact model and series or can I use any similar capacit

You need to show some pictures of where the old caps are, otherwise it's impossible to give recommendations about the replacements.

[ChaosLegionnaire]

Re: Do I need to use the same exact model and series or can I use any similar capacit

Also, when soldering, I'm new to this as well, I notice that my iron doesn't melt the solder to liquid, it melts it and then it falls down into a ball. Is my soldering iron not hot enough? Its a radioshack brand, and I'm using the 40W setting (highest it goes). Ive never tinned my iron because as I try to it just makes the solder fall off into a ball, so it doesn't stick to the iron.

your tip is badly oxidised thus the solder will no longer adhere to it. an oxidised tip can also no longer transfer heat as effectively to the solder joint thus the solder on the pcb wont melt. always tin your tip the first time u use it and then wipe it with the wet sponge to prevent it from oxidising. also dont let it heat up for too long the first time or it becomes oxidised and u can no longer tin it due to non-adherence of the solder.

u can also use a tip refresher like this goot tip refresher which burns off the oxide layer and retins the tip for u at the same time. however, be warned that it is acidic so u will need to wipe the tip with a wet sponge after dipping it in the tip refresher then rinsing the sponge and wiping the tip a few times to get rid of all traces of acid or else the acidic residue will corrode the pcb traces.

for me, the cost of the tip refresher cost as much as a new tip so it made economical sense to get the tip refresher to retin any badly oxidised tips i had in future to salvage them rather than keep buying new tips.

[stj]

Re: Do I need to use the same exact model and series or can I use any similar capacit

you may be using shit solder,
the chemical mix in the flux makes a huge difference between solders.

if you need to solder brass btw, make sure the flux has Halide in it.

[giyad]

Re: Do I need to use the same exact model and series or can I use any similar capacit

You need to show some pictures of where the old caps are, otherwise it's impossible to give recommendations about the replacements.

I attached a picture.

So the ones I circled in red are the Rubycon MCZ, the ones in blue are the Rubycon MFZ, and the ones circled in green are the Samxon GC.

[giyad]

Re: Do I need to use the same exact model and series or can I use any similar capacit

your tip is badly oxidised thus the solder will no longer adhere to it. an oxidised tip can also no longer transfer heat as effectively to the solder joint thus the solder on the pcb wont melt. always tin your tip the first time u use it and then wipe it with the wet sponge to prevent it from oxidising. also dont let it heat up for too long the first time or it becomes oxidised and u can no longer tin it due to non-adherence of the solder.

u can also use a tip refresher like this goot tip refresher which burns off the oxide layer and retins the tip for u at the same time. however, be warned that it is acidic so u will need to wipe the tip with a wet sponge after dipping it in the tip refresher then rinsing the sponge and wiping the tip a few times to get rid of all traces of acid or else the acidic residue will corrode the pcb traces.

for me, the cost of the tip refresher cost as much as a new tip so it made economical sense to get the tip refresher to retin any badly oxidised tips i had in future to salvage them rather than keep buying new tips.

Does the image I attached of my tip look like its oxidized? Its the first time I use the soldering iron, so it shouldn't be oxidized, but my .022" diameter lead-free solder is not sticking to the tip.

[stj]

Re: Do I need to use the same exact model and series or can I use any similar capacit

your iron got too hot - it takes a lot to blue the metal!

[giyad]

Re: Do I need to use the same exact model and series or can I use any similar capacit

your iron got too hot - it takes a lot to blue the metal!

It can get too hot?

I filed it down and got it shiny again, and then tried to get some solder on it. I actually was able to, but not on the tip of the tip, just around the angle. I tried then putting it to my board, but the caps are soldered on there pretty well, I guess I need some solder braid to make sure the solder comes off before it just hardens back on.

[ChaosLegionnaire]

Re: Do I need to use the same exact model and series or can I use any similar capacit

it looks like the mcz rubies are for the cpu vrm input filtering. over there, esr and ripple matter the most. therefore, the uhw u linked cannot be used as they have inferior esr and ripple to the mcz. the mcz 10x25mm has an esr of 9 mOhms and 3230 mA rms of ripple handling. suitable replacements would be nichicon hn and hz or u can try polymodding with 330uF or 470uF 16v poly caps. suitable series for polymodding would be sanyo/panasonic oscon sepc, ncc/ucc psc or nichicon fpcap.

as for the mfz rubies and samxon gc, they look like they are being used for the vrm in and out of the northbridge but i could be wrong. but if im right, then u basically have the same situation as the mcz. the replacements must have equal to or better esr and ripple rating than the originals for vrm usage.

btw, the way your caps failed is quite bad. the caps have even vented their internal goo. bloated caps is one thing but a leaking cap from the vent is another. this suggests serious overheating of your board. i strongly recommend besides replacing the caps, u improve the cooling and ventilation of your case to prolong the life of the caps or else you'll be doing this exercise again a few years in the future with bloated caps again. and even then, it may not be just the caps that have failed the next time due to the heat! if the bga solder fails, its going to be a highly technical and tricky exercise with a hot air gun and soldering flux trying to reflow the chipset or other stuff!

Does the image I attached of my tip look like its oxidized? Its the first time I use the soldering iron, so it shouldn't be oxidized, but my .022" diameter lead-free solder is not sticking to the tip.

eeks, i just saw the image of your board as i was posting my msg. at first, i thought we were dealing with a p4 or pentium-d era leaded solder board due to the electrolytics caps. but then i saw the q6600 lga775 socket and the nvidia logo on the northbridge heatsink and i realised we were dealing with a rohs lead-free solder board! u said u had a 40w iron? im afraid that is inadequate wattage for desoldering/soldering a lead-free solder board. u need at least 60w or maybe even 80w or more because lead-free solder melts at a much higher temperature than leaded solder so u need a high wattage iron to maintain the high temps to keep the solder at its liquidus temperature while u desolder.

so i dont think its your tip. its just the wattage of your iron is inadequate for lead-free soldering/desoldering.

also, lead-free solder is a pain to work with by hand especially for a newbie soldering for the first time. i suggest u use rosin core 60/40 leaded solder instead. dont worry, u wont get poisoned by the lead. just dont inhale the soldering fumes and wash your hands after u're done soldering and u'll be fine. u need to add a dab of leaded solder to the lead-free solder joint, its okay to do this. this lowers the melting temp of the lead-free solder making it much more easier to melt and desolder the caps.

your iron got too hot - it takes a lot to blue the metal!

i thought soldering irons are supposed to come with a thermostat to cut off the heating element if the temperature got too hot. i dont know much about the build quality of radioshack irons to comment further. i.e. if they properly calibrated their thermostats or not.

[giyad]

Re: Do I need to use the same exact model and series or can I use any similar capacit

Can you recommend an iron for this job? Would this or this be a good candidate? I might need a more precise tip for the first one, but these get up to 80W.

I'd prefer to use lead free solder, since the board itself as you say is lead-free. I did use a similar iron a few years back to repair the caps on a monitor, that worked out well, and I used the same lead-free solder. I'll get a better iron if that is what you think is the issue with my board though. I'm just not able to melt the solder and remove it to clear the way for the pins to come out of their holes. Gonna get a solder braid to help with that.

In regards to the caps. I have been told that the only things which matter are the Voltage and uf. I can't find any caps on mouser that qualify what you said with the same exact voltage, uf, and then ESR and Ripple. I found these, do you think they will work? They all say obsolete by the manufacurer but they don't suggest substitutes, they're still available though..

Nichicon UHN replacing Rubycon 16V 1800uf MCZ, 10mm diameter, 25mm height
Nichicon UHW replacing Rubycon 6.3V 2700uf MFZ, I dont have the ripple or ESR of this one. Can't find it online, 10mm diameter, 20mm height
Nichicon UHM replacing Samxon 6.3V 1500uf GC, 8mm diameter, 12mm height

What matters when replacing a capacitor? The Voltage, Capacitance, ESR, Ripple, how about size? If any of these don't have to be exact, do they need to be greater or lower? For example, voltage needs to be equal or greater otherwise it will burst.

Thanks for the advice about the caps, the computer was great for 8 years and then this year started rebooting on me. I think it was due to probably one capacitor but since I just kept letting it boot it probably blew out the others as well. Didn't actually hear anything burst.

[stj]

Re: Do I need to use the same exact model and series or can I use any similar capacit

i thought soldering irons are supposed to come with a thermostat to cut off the heating element if the temperature got too hot. i dont know much about the build quality of radioshack irons to comment further. i.e. if they properly calibrated their thermostats or not.

no, only variable ones do.
the cheap-assed "hobby" irons are just a directly connected element.

[ChaosLegionnaire]

Re: Do I need to use the same exact model and series or can I use any similar capacit

I did use a similar iron a few years back to repair the caps on a monitor, that worked out well, and I used the same lead-free solder. I'll get a better iron if that is what you think is the issue with my board though.

umm... a monitor pcb is different from a motherboard pcb which is a many multi layer pcb. a monitor pcb may have less layers than a mobo pcb so u can get away with using lower wattage irons. mobo pcbs also have a LOT of copper in them compared to monitor pcbs. the copper acts as a heatsink sucking the heat away from your iron tip.

unfortunately, i cannot advise u on soldering irons as i only use cheapskate generic "disposable" irons. maybe someone else more "professional" with soldering irons can help u with that.

In regards to the caps. I have been told that the only things which matter are the Voltage and uf. I can't find any caps on mouser that qualify what you said with the same exact voltage, uf, and then ESR and Ripple.

What matters when replacing a capacitor? The Voltage, Capacitance, ESR, Ripple, how about size? If any of these don't have to be exact, do they need to be greater or lower? For example, voltage needs to be equal or greater otherwise it will burst.

what matters when replacing a cap is what it will be used for like what per hansson said. we need to know where the caps are on the pcb so we know what the caps are being used for so that we can know better which specs of the cap matter more.

voltage and uf only matter for general purpose filtering. vrm usage is a specialized type of filtering and is a different matter altogether. cpu or gpu vrm caps need ultra-low esr and ultra-high ripple to maintain stability of the cpu/gpu during transient load.

the can size of a cap is what affects its esr and ripple. generally, larger can sizes will have lower esr and higher ripple rating. if u look at the datasheets of some caps, u'll notice the caps with the same can size but different uf and voltage have the same esr and ripple.

I found these, do you think they will work? They all say obsolete by the manufacurer but they don't suggest substitutes, they're still available though.
Nichicon UHW replacing Rubycon 6.3V 2700uf MFZ, I dont have the ripple or ESR of this one. Can't find it online, 10mm diameter, 20mm height

mfz is a customised order so the datasheets are not released to the public but they should be rather similar in specs to nichicon hz. if hz is unavailable, u can go for hn instead but the uf needs to be raised a bit to 3300 due to the inferior esr and ripple rating.

[giyad]

Re: Do I need to use the same exact model and series or can I use any similar capacit

what matters when replacing a cap is what it will be used for like what per hansson said. we need to know where the caps are on the pcb so we know what the caps are being used for so that we can know better which specs of the cap matter more.

How can I get you exact locations for the caps on the motherboard? Or does that picture I posted suffice? Just trying to see if the caps I chose are good replacements so I can order them and start soldering. I definitely know that these are all pretty close to the CPU.

I can't find the HN or HZ Nichicons in stock. Would like to get a replacement without waiting weeks if possible. If all that matters is the ESR and the Ripple since these are on the northbridge, I think the ones I found are good, except for the replacement of the MFZ because I have no idea what the ESR or Ripple are. What I can do is buy the MFZ Rubycons from ebay, but I didn't want to do that because all the posts advise against using ebay because of knock offs.

What matters when replacing a capacitor? The Voltage, Capacitance, ESR, Ripple, how about size? If any of these don't have to be exact, do they need to be greater or lower? For example, voltage needs to be equal or greater otherwise it will burst. Can capacitance, ESR, and Ripple be higher or lower than the one I have? Size seems to matter just because of space, I can't go larger because they won't fit. Frequencies aren't given, so does Impedance matter or can I just assume 100KHz, making impedance and ESR pracitcally the same?

Appreciate all your help on this by the way!

[stj]

Re: Do I need to use the same exact model and series or can I use any similar capacit

replace the MFZ with polymer caps