Can be simple electrolytic capacitor replaced by polymer capacitor? - Page 1
Forum section: electronics / beginners

author: Ivanko1
author_rank: Contributor
timestamp: August 29, 2015, 05:06:06 pm
content: My old videocard starting make artefacts, so I decided to clean up her cooler.When I remove heatsink - I notice what one of the electrolytic capasitor (like this) is beign bulging. So I solder him off and replaced by SMD style for surface mounting of aluminum electrolytic capacitors with polymer electrolyte (like this) from old plasma TV. With the same value.Is it possible trade? Videocard is working fine so far. I think it was capacitor on a 12 volt powering line.P.s. Sorry for my english.)

author: Zero999
author_rank: Super Contributor
timestamp: August 29, 2015, 05:19:01 pm
content: That should be fine, as long as you don't expect a used component to have the same life as a new one.How can you be sure it's an aluminium polymer capacitor? That package is used for plain old aluminium capacitors too.

author: Cliff Matthews
author_rank: Unknown
timestamp: August 29, 2015, 05:25:32 pm
content: Is the capacitor of the same value and temp rating?You can test by putting the GPU under load. eg:http://www.ozone3d.net/benchmarks/fur/

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 29, 2015, 05:35:51 pm
content: Is the VOLTAGE rating of your replacement capacitor at least as high as the original capacitor?AND...Is the CAPACITANCE rating of your replacement capacitor at least as much as the original capacitor?The nature of the electrolyte is not nearly as important as the capacitance and voltage ratings.Besides, it is not clear why you think your replacement capacitor is "polymer"? Or why it makes any difference?It seems like you are concentrating on minor factors and ignoring the important parts.

author: Ivanko1
author_rank: Contributor
timestamp: August 29, 2015, 10:39:31 pm
content: Thank you for interesting my question.Voltage and capacitance are the same 16v and 470microF.Here is a photo of old one and same capacitors on pcb from old TV (what I call "polymer").My Uni-T61 shows 40microF on old (that bulging) capacitor and about 450microF on replaced smd.Unfortunately I don't have a new capacitor with the same capacictance and voltage, or same size. I have one new, but much bigger CapXon 470mF 35V 105"C Low ESR - I think he wouldnt fit in notch in heatsink.(Find good radiodetails in my country - it is a big problem, aspecially fast and in my town, mostly cheap and creapy chineese jobbing... Used parts - most accessible.Best manufacurer I have seen - Jamicon, CapXon (mostly), SAM, SAMWHA.The brown electrolytic capacitor on a second photo - also have good conditions: 470mcF (450mcF tested) 105"C, but 35v and bigger size - maybe he will be better?I will try find a new real polymer capacitor and replace as fast as I can.)Also have another question about capacitors in aluminium shell - whether a short circuit if they come into contact with-each-other or other parts? I suspect this is wrong, but I have to ask.)

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 30, 2015, 12:11:45 am
content: Assume that the metal can of a capacitor IS connected to one end of the capacitor, typically the "negative" end. It is NOT safe to allow anything to touch the outside case of a capacitor.Of course there are some capacitors that have plastic around them, typically heat-shrink tubing with the identification printed for capacitor value, etc.

author: Cliff Matthews
author_rank: Unknown
timestamp: August 30, 2015, 02:01:19 am
content: I can't resist... "I spy with my little eye" (a piece bit of copper wire between C1038 and C1046)...

author: Ivanko1
author_rank: Contributor
timestamp: August 30, 2015, 06:25:10 am
content: No, it's not a copper, just some seed or needle from new year tree.)I check connections pins and shell - there was more than Mega Ohms. But for shure - I make one turn of duct tape around of it, becauce main heatsink are very tight there.

author: Ivanko1
author_rank: Contributor
timestamp: September 08, 2015, 10:48:45 am
content: My friend brought me from the capital of the new real polymer capacitor with the same parameters, but it is slightly larger and prevents radiator proper fit to the chip. So I solder it from the other side of the board - he blowing from the CPU and north bridge coolers.So now all is well. I think.)

author: Richard Head
author_rank: Frequent Contributor
timestamp: September 08, 2015, 11:44:23 am
content: At the risk of sounding pedantic simply swopping a wet electrolytic output cap with a superior solid type can result in a control loop instability due to the (generally) lower ESR of the solid polymer capacitor.The op-amp error amplifier transfer function will have been tailored around the location of the zero caused by the original capacitor ESR and output capacitance value. Try to use the same cap value, voltage and physical size if possible to avoid a potential problem.

author: DimitriP
author_rank: Super Contributor
timestamp: September 08, 2015, 12:06:43 pm
content: QuoteYou can replace anything with anything as long as:A) It doesn't blow up when you power it on.B) it worksC) It still works a week laterSo well done on a successful repair !

author: DimitriP
author_rank: Super Contributor
timestamp: September 08, 2015, 12:20:55 pm
content: Quote from: Richard Head on September 08, 2015, 11:44:23 amQuote

author: Gyro
author_rank: Super Contributor
timestamp: September 09, 2015, 09:17:03 am
content: QuoteQuoteYou're not going to win many friends with an attitude like that pal!

author: wraper
author_rank: Unknown
timestamp: September 09, 2015, 10:57:37 am
content: When replacing low ESR electrolytic capacitor with polymer capacitor, generally capacitance of replacement should be about 3 times less. As ESR and ripple current rating is what matters in such uses, not capacitance.Quote from: DimitriP on September 08, 2015, 12:06:43 pmAnd then it dies after a bit more. Approach used by fuckwit repair technicians. If it works 2 years later, you can call it successful repair. You can replace LOW ESR capacitors with general purpose ones too, they'll certainly last way more than a week, but no more than half a year.As I work in repair business, in many years have seen plenty of such retards and fruits of their labor.