Is this the right capacitor? - Page 1
Forum section: electronics / beginners

author: ASHOT3359
author_rank: Newbie
timestamp: June 21, 2023, 06:40:16 am
content: A little background: I'm learning to solder to fix my old graphics cards for fun. Two weeks ago, I didn’t know how watts differ from volts and what a short circuit is. So just in case explain everything to me like I'm 5 years old.In the photo, all capacitors in a row should be the same (Black ones, 16v and 270 something). I changed one of them because it looked a little "puffy" on the top. I checked the old one with a multimeter, it seems to behave the same way as the new white ones. Did I buy the right one? Or is it better to insert the original back.p.s. Went through hell to get him out, using ways that make me think i burned and tore everything inside. Oh well. After that I have to change 1-2 mosfet drivers.

author: mengfei
author_rank: Regular Contributor
timestamp: June 21, 2023, 07:02:29 am
content: looks ok to me But unless you have the right tool & equipment to repair a 6 layer or even a 12 layer board you won't get that far w/o breaking other parts more so the PCB trace & pads.....so did work?

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 21, 2023, 07:29:57 am
content: It should be fine. Bulk capsusuallydon't need exacting parameters anyway.Quote from: ASHOT3359 on June 21, 2023, 06:40:16 amNow I'm concernedI assume you at least got hot air/rework station.

author: ASHOT3359
author_rank: Newbie
timestamp: June 21, 2023, 07:33:24 am
content: Not yet, the main problem is one (probably 2) of the mosfets (i hope, so i don't need to keep searching) Checked them with bench supply and multimeter set to millivolts. One is not good, the other is worse. Then i plug it in my test rig the card comes to life for a moment and that exact (worse) mosfet driver is lighting up in my thermocamera.equipment...well. I guess i don't have a pre heater, and this usb microscope is not enough. Should i invest in the preheater? Any recommendations?

author: ASHOT3359
author_rank: Newbie
timestamp: June 21, 2023, 07:40:38 am
content: Yeah i got HotAirGun. Used it to desolder capacitor in question. That, and 2 rusty sewing pins. Hope i didn't destroy anything then i was forcing them out with pliers

author: 807
author_rank: Frequent Contributor
timestamp: June 21, 2023, 09:36:54 am
content: Quote from: ASHOT3359 on June 21, 2023, 06:40:16 amWhat range did you have your meter on to check the capacitors?You need to measure capacitance & ESR.Can you post a photo of the puffy capacitor?

author: ASHOT3359
author_rank: Newbie
timestamp: June 22, 2023, 11:52:16 am
content: Quote from: 807 on June 21, 2023, 09:36:54 amIt is a auto range multimeter. Switched to the symbol -||- it shows around 250uf. All of the new ones show 280-290. Close enough? Don't have a tool to check ESR but i ordered it, should arrive tomorrow. What considered bad ESR?Quote from: 807 on June 21, 2023, 09:36:54 amIt's hard to see the "swelling" on the photo, so i'll show it on a video. You can see how the capacitor i'm holding slightly warps the reflections while the one on the board does not.https://drive.google.com/file/d/1-R17Z19uUl6xWu19L6f9uEltM8luS4JQ/view?usp=sharing

author: wraper
author_rank: Unknown
timestamp: June 22, 2023, 12:01:15 pm
content: This is an aluminum polymer capacitor, no liquid electrolyte to dry out. If it was a normal electrolytic, you would see a vent pattern on top. And this is not swelling, just manufactured not perfectly flat. 250uF is well within spec which usually is +/-20%.

author: ASHOT3359
author_rank: Newbie
timestamp: June 22, 2023, 04:50:38 pm
content: I have to put it back now ... shit. Tnx you all.Oh btw, can somebody tell me a good way to isolate capacitors from hot air?

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 22, 2023, 06:02:23 pm
content: Quote from: ASHOT3359 on June 22, 2023, 04:50:38 pmSMD ceramics? Typically it can withstand some amount of hot time.