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| adding capacitors to a PC power supplies output [ project ] |
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| forestelf:
--- Quote from: mariush on March 25, 2019, 12:43:14 am ---Yes, that's big capacitor is the main one which will have up to 400-420v DC on it while the power supply runs. Right near it, there's a "bleeder resistor"which slowly discharges the capacitor as soon as the psu is turned off. However, sometimes these resistors aren't installed or they're broken, so it's possible to have high voltage on that capacitor after psu is shut down. So NEVER assume that capacitor is discharged. Safest would be to get a multimeter and MEASURE the voltage on its terminals before you get close to it. If there's more than around 10-20v on it, discharge it. You COULD just use a screwdriver and make a short circuit between the two terminals, but if there's a lot of energy in the capacitor you can damage the screwdriver and in rarer cases even the circuit board if you just short the capacitor with a screwdriver. Safer method would be to get a resistor (let's say 100 ohm 1w or higher) and carefully connect the resistor between the terminals for a few seconds and then measure voltage again with multimeter. regarding color on polymer capacitors - it's mostly related to who manufacturers them, some company may prefer RED (for example nichicon), other may prefer light blue (I think teapo for example), others use the plain black or gray. You can often tell which manufacturer is by the series - for example FP is an indicative of "nichicon fp series", fp being short for "functional polymer" or something like that. In one of your posts, there's one with FP and 49cr written on it - FP is series, 49cr is factory code, like manufacturing date or extra series information, and then there's 2 numbers ... the one ending with 1 is the capacitance in short form ... like for example 471 means 47 x 101 = 470uF , and the last line 16 means voltage, 16v. In another picture there's some light blue capacitors, those are made by Nippon Chemi Con / United Chemi Con - i can tell that because of the tiny "hat", the small rectangle like thing over the text Here's an example (click on picture to see what i mean) : https://www.digikey.com/product-detail/en/united-chemi-con/APSC6R3ELL152MJB5S/565-3229-ND/1826693 In your picture, you easily see the capacitance (330uF - in long form because the capacitor is wide enough to fit more than 3 digits), and 16 which means voltage rating. The series may be determined (or not) from the letter and numbers above capacitance. There's usually enough room on these capacitors to have capacitance and voltage written on them Yes, there's differences between them, like ripple current values, esr etc, but in power supplies you want polymer with very low esr and high current ripple so there's a bunch of series with similar values, therefore you don't have to use the exact series from the exact maker. Don't mess with the main capacitor, won't make any difference and it's from a quality manufacturer. --- End quote --- i appreciate you sharing your knowledge;' if this project entailed removing caps i wouldent of considered it+the main capacitor isnt something i was really planning on anyways to be honest, ( also lol@damaging the screwdriver XD thts last priorities there :P ) so i have a question, on capacitors you linked, the c 929 marking at the top of it, what does it mean, dosent match the short form you explained as the number is allready written below but if i compare it to the one in my second post or so the one there is c 529 , is this number a specification or something not as relevant such as factory or date made kinda thing? i figure there suitable for the task of the front panel location and the price was fine so i was trying to compare it down to the last details - also what does ripple current at low frequency represent? (looking at caps trying to find something) if its over 600ma at 120khz will it not have effect on the 60mv ripple |
| TimNJ:
--- Quote from: forestelf on March 27, 2019, 04:06:17 pm --- --- Quote from: mariush on March 25, 2019, 12:43:14 am ---Yes, that's big capacitor is the main one which will have up to 400-420v DC on it while the power supply runs. Right near it, there's a "bleeder resistor"which slowly discharges the capacitor as soon as the psu is turned off. However, sometimes these resistors aren't installed or they're broken, so it's possible to have high voltage on that capacitor after psu is shut down. So NEVER assume that capacitor is discharged. Safest would be to get a multimeter and MEASURE the voltage on its terminals before you get close to it. If there's more than around 10-20v on it, discharge it. You COULD just use a screwdriver and make a short circuit between the two terminals, but if there's a lot of energy in the capacitor you can damage the screwdriver and in rarer cases even the circuit board if you just short the capacitor with a screwdriver. Safer method would be to get a resistor (let's say 100 ohm 1w or higher) and carefully connect the resistor between the terminals for a few seconds and then measure voltage again with multimeter. regarding color on polymer capacitors - it's mostly related to who manufacturers them, some company may prefer RED (for example nichicon), other may prefer light blue (I think teapo for example), others use the plain black or gray. You can often tell which manufacturer is by the series - for example FP is an indicative of "nichicon fp series", fp being short for "functional polymer" or something like that. In one of your posts, there's one with FP and 49cr written on it - FP is series, 49cr is factory code, like manufacturing date or extra series information, and then there's 2 numbers ... the one ending with 1 is the capacitance in short form ... like for example 471 means 47 x 101 = 470uF , and the last line 16 means voltage, 16v. In another picture there's some light blue capacitors, those are made by Nippon Chemi Con / United Chemi Con - i can tell that because of the tiny "hat", the small rectangle like thing over the text Here's an example (click on picture to see what i mean) : https://www.digikey.com/product-detail/en/united-chemi-con/APSC6R3ELL152MJB5S/565-3229-ND/1826693 In your picture, you easily see the capacitance (330uF - in long form because the capacitor is wide enough to fit more than 3 digits), and 16 which means voltage rating. The series may be determined (or not) from the letter and numbers above capacitance. There's usually enough room on these capacitors to have capacitance and voltage written on them Yes, there's differences between them, like ripple current values, esr etc, but in power supplies you want polymer with very low esr and high current ripple so there's a bunch of series with similar values, therefore you don't have to use the exact series from the exact maker. Don't mess with the main capacitor, won't make any difference and it's from a quality manufacturer. --- End quote --- i appreciate you sharing your knowledge;' if this project entailed removing caps i wouldent of considered it+the main capacitor isnt something i was really planning on anyways to be honest, ( also lol@damaging the screwdriver XD thts last priorities there :P ) so i have a question, on capacitors you linked, the c 929 marking at the top of it, what does it mean, dosent match the short form you explained as the number is allready written below but if i compare it to the one in my second post or so the one there is c 529 , is this number a specification or something not as relevant such as factory or date made kinda thing? i figure there suitable for the task of the front panel location and the price was fine so i was trying to compare it down to the last details - also what does ripple current at low frequency represent? (looking at caps trying to find something) if its over 600ma at 120khz will it not have effect on the 60mv ripple --- End quote --- Don't worry about the CXXX marking on the cap. The 'C' probably just indicates PSC, the series from United Chemi-Con. The other digits are likely a manufacturing date code or factory identifier as you mentioned. The ripple current rating of an electrolytic/polymer capacitor basically says: "You can run this capacitor at both the stated ripple current spec and at the rated operating temperature (105C typically), and expect to get the stated life expectancy (1,000 - 15,000 hours typically). The ripple current spec is fundamentally a function of the capacitors equivalent series resistance (ESR). The lower the ESR, the higher the ripple current spec. This is pretty intuitive because a higher ESR means the capacitor will dissipate more heat internally, leading to a higher core temperature, and shortened life. |
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