Caps…so many of same to choose from

Thread Starter

robismod

Joined Sep 22, 2015
217
I went to Digi site to order some replacement caps. I entered the values and I get quite a few results/prices and I see a variety of manufacturers. This is for an LG home monitor repair…so many choices for each cap…470mf, 35v and 1000mf, 16v.
(While I’m in there I see a couple more, 33mf, 50v, and .47mf 50v)
Any particular brands I should lean to?
Thanks much!
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
Digikey are quite reputable, when it comes to quality.
Another important issue is the composition, the larger values will be Electrolytic, the others could be ceramic or poly etc.
The higher price for the same value obviously points to a higher composition in general.
 

WBahn

Joined Mar 31, 2012
29,979
I went to Digi site to order some replacement caps. I entered the values and I get quite a few results/prices and I see a variety of manufacturers. This is for an LG home monitor repair…so many choices for each cap…470mf, 35v and 1000mf, 16v.
(While I’m in there I see a couple more, 33mf, 50v, and .47mf 50v)
Any particular brands I should lean to?
Thanks much!
You see surprised that capacitors come in not only different voltage ratings, but also drastically different capacitances (your four examples represent a span of well over three orders of magnitude).

What were you expecting? That a capacitor is a capacitor and you should be able to replace any capacitor with any other capacitor?

That's a serious question, by the way. It's not unreasonable for someone that has never had anything to do with electronic components to think that all capacitors are (or at least should be) essentially the same. What were your expectations?

Ideally, a capacitor is a device that stores a charge separation that is proportional to the voltage applied to it. But while one capacitor might store a picocoloumb per volt, others store a coulomb per volt, so the second stores a million, million times as much. One way of visualizing how big a span they range, consider that the largest supercapacitor on Digikey (that I found) is rated at 13,500 F. Now let's equate this to a room that can hold all of humanity, all 300 million metric tons of us. At the other end of the spectrum, the smallest capacitor sold by Digikey (again, that I found) is 0.1 pF. That's a ratio of 1.35x10^17, which would then equate to a room that can hold about 2 mg. A typical 20 lb bond letter-size piece of paper weighs about 4.5 g, so the room could only hold a piece of paper that was about 0.2" on a side.

As amazing as that is, now consider that the reason why manufacturers make capacitors that span that kind of range is because there are enough applications for each of those sizes to create a viable market.

That's just the capacitance. The next big characteristic is the voltage. Like all physical devices, capacitors have limitations. Some capacitors can withstand thousands of voltage, while others will be destroyed by just a few volts. In general, two otherwise identical capacitors but where one can withstand 10 V and other 1000 V, the latter will be larger and more expensive. It will likely have other characteristics that had to be sacrifices in order to get it to stand up to that higher voltage.

Then there are many other characteristics that are critically important for some applications and don't matter at all for others.

That's were the fun comes in as a designer (or a repairman). Which characteristics matter for a given use of a given capacitor in a given product?
 

Thread Starter

robismod

Joined Sep 22, 2015
217
You see surprised that capacitors come in not only different voltage ratings, but also drastically different capacitances (your four examples represent a span of well over three orders of magnitude).

What were you expecting? That a capacitor is a capacitor and you should be able to replace any capacitor with any other capacitor?

That's a serious question, by the way. It's not unreasonable for someone that has never had anything to do with electronic components to think that all capacitors are (or at least should be) essentially the same. What were your expectations?

Ideally, a capacitor is a device that stores a charge separation that is proportional to the voltage applied to it. But while one capacitor might store a picocoloumb per volt, others store a coulomb per volt, so the second stores a million, million times as much. One way of visualizing how big a span they range, consider that the largest supercapacitor on Digikey (that I found) is rated at 13,500 F. Now let's equate this to a room that can hold all of humanity, all 300 million metric tons of us. At the other end of the spectrum, the smallest capacitor sold by Digikey (again, that I found) is 0.1 pF. That's a ratio of 1.35x10^17, which would then equate to a room that can hold about 2 mg. A typical 20 lb bond letter-size piece of paper weighs about 4.5 g, so the room could only hold a piece of paper that was about 0.2" on a side.

As amazing as that is, now consider that the reason why manufacturers make capacitors that span that kind of range is because there are enough applications for each of those sizes to create a viable market.

That's just the capacitance. The next big characteristic is the voltage. Like all physical devices, capacitors have limitations. Some capacitors can withstand thousands of voltage, while others will be destroyed by just a few volts. In general, two otherwise identical capacitors but where one can withstand 10 V and other 1000 V, the latter will be larger and more expensive. It will likely have other characteristics that had to be sacrifices in order to get it to stand up to that higher voltage.

Then there are many other characteristics that are critically important for some applications and don't matter at all for others.

That's were the fun comes in as a designer (or a repairman). Which characteristics matter for a given use of a given capacitor in a given product?
Whew! That’s a bit broad there…let me try and address some of it…
First, I’m 63 years old, and have been a “tinkerer” and “Jack of all trades” most of my life. I’ve been agitated many times over those years at my lack of deeper knowledge in many areas, but it never stopped me, and usually I’d figure things out. (Kudos to forums like this and YouTube that in recent years have probably helped me in staying alive, and made my efforts easier)
“Surprised…come in different voltage ratings and capacitance”? I don’t see where that came from—I specifically mentioned the exact pieces I wanted to replace (in case somehow it mattered for an answer) and then I noted that there were quite a few to choose from. (Maybe I should have added “the exact values”)
And “what was I expecting”? Why yes, I could have “replaced a cap with any other cap” (as long as it had the same values) but in this case, there were a bunch of different brand names, and prices varying from one extreme to another. Simply, all I was asking was for my purpose of a simple LG monitor, did anyone want to offer the brands they trusted/liked.
But, the rest of your post I did enjoy, really deep for my aging brain. Thanks for your reply. (Smile)
 

MrChips

Joined Oct 2, 2009
30,720
I don't choose my capacitor purchases based on brand.
Here are my purchasing criteria in order of importance.

1) The value of the capacitance in microfarads, written as μF or MF (mf means something else)
2) Operating DC voltage (assuming that it is for DC application)
3) Electrolytic or non-electrolytic, polar or non-polar
4) Material, aluminum or tantalum (assuming that it is electrolytic capacitor)
5) Lead orientation, radial vs axial and connection style, i.e. SMD, thru hole, spade, screw terminals
6) Physical dimensions
7) Mounting hardware required
8) Plus a bunch of other parameters if they are critical, i.e. tolerance, temperature, ESR effective series resistance.

Hopefully now you can understand why your possible choices range in the thousands or hundreds of thousands.

Criteria such as availability, cost, shipping charges, volume discounts, supplier location and brand are all secondary.
 

sagor

Joined Mar 10, 2019
903
I went to Digi site to order some replacement caps. I entered the values and I get quite a few results/prices and I see a variety of manufacturers. This is for an LG home monitor repair…so many choices for each cap…470mf, 35v and 1000mf, 16v.
(While I’m in there I see a couple more, 33mf, 50v, and .47mf 50v)
Any particular brands I should lean to?
Thanks much!
Another thing to look out for is temperature rating. Some are rated 85C, others 105C. There are other values as well, but those 2 are the most common. If you suspect the old caps are bulging, and were rated 85C, maybe try the 105C caps instead. You can also see that some caps are rated at so many hours at maximum temperature, like 1000hrs, 2500hrs, etc.
Watch out for the size, make sure any replacements fit properly...
 

Thread Starter

robismod

Joined Sep 22, 2015
217
I don't choose my capacitor purchases based on brand.
Here are my purchasing criteria in order of importance.

1) The value of the capacitance in microfarads, written as μF or MF (mf means something else)
2) Operating DC voltage (assuming that it is for DC application)
3) Electrolytic or non-electrolytic, polar or non-polar
4) Material, aluminum or tantalum (assuming that it is electrolytic capacitor)
5) Lead orientation, radial vs axial and connection style, i.e. SMD, thru hole, spade, screw terminals
6) Physical dimensions
7) Mounting hardware required
8) Plus a bunch of other parameters if they are critical, i.e. tolerance, temperature, ESR effective series resistance.

Hopefully now you can understand why your possible choices range in the thousands or hundreds of thousands.

Criteria such as availability, cost, shipping charges, volume discounts, supplier location and brand are all secondary.
Yes sir—that is understood…and all things considered, how about…just pick a name for me? Or maybe since they carry all good brands, I’ll just close my eyes and pick one.
Thanks though for the insight. I do appreciate it.
 

Thread Starter

robismod

Joined Sep 22, 2015
217
Another thing to look out for is temperature rating. Some are rated 85C, others 105C. There are other values as well, but those 2 are the most common. If you suspect the old caps are bulging, and were rated 85C, maybe try the 105C caps instead. You can also see that some caps are rated at so many hours at maximum temperature, like 1000hrs, 2500hrs, etc.
Watch out for the size, make sure any replacements fit properly...
Ahhhh…I have to admit, that element escaped me, and I will look into that. I actually have 3 that are bulging. Thanks much.
 

sagor

Joined Mar 10, 2019
903
Ahhhh…I have to admit, that element escaped me, and I will look into that. I actually have 3 that are bulging. Thanks much.
Bulging caps are one of the most common failure in places like power supplies. Those are one of the first thing to look for. Often, it is best to replace all the electrolytic caps on the same power supply board, as once one bulges, others are often close behind...
 

Thread Starter

robismod

Joined Sep 22, 2015
217
Well…I closed my eyes, circled my finger around in the air a few times, then landed on my “picked” caps. (Of course I had filtered the choices down to the values needed)
Ordered, received, installed. Monitor works like a champ now. Again, thanks for all the input.
 
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