Can someone explain me how to read/find that capacitor? - Page 1
Forum section: electronics / beginners

author: TheGenesis
author_rank: Contributor
timestamp: November 11, 2018, 01:35:59 pm
content: I found a dead cap on a graphic card, but i'm not shure if this is a 10pf ceramic/tantalum or just a seller marking.Can someone tell me how to read such a thing?

author: Twoflower
author_rank: Frequent Contributor
timestamp: November 11, 2018, 01:50:39 pm
content: That's for sure not a 10pF cap. As you can see it is polarized and there are no such small caps that are polarized.I would more say that's a 100µF solid electrolytic cap. Looking a bit around it looks like that one is a Panasonic TQC Series cap. And here's the datasheet:https://industrial.panasonic.com/cdbs/www-data/pdf/AAA8000/AAA8000C62.pdfaccording to that it's indeed a 100µF Cap, with 16V (that's the C from C3N).How do you came to the idea that that that one is defect?

author: TheGenesis
author_rank: Contributor
timestamp: November 11, 2018, 03:47:17 pm
content: Because it reads megaohms and intermittent a couple of kiloohms. And its not charging like other caps on this pcb with (although) higher capacities e.g. "470 e3N".Or my Multimeter is probably not accurate enough.

author: Twoflower
author_rank: Frequent Contributor
timestamp: November 11, 2018, 03:56:12 pm
content: That could caused by other circuits that are connected to the cap. Measure parts in circuit might led to false results. One possible reason for your observation: Attaching the Multimeter charges the cap until a certain voltage. That voltage triggers another part of the circuit that discharges the cap and cause the kOhm reading.That behavior you see would be a rather uncommon defect. Static short or open or a constant resistance is more likely to be a defect.Measure parts in circuit might give an indication, but cal you also led to wrong conclusions. Especially if you don't have knowledge of the surrounding circuit.

author: TheGenesis
author_rank: Contributor
timestamp: November 11, 2018, 04:41:45 pm
content: Thanks for the advise. I'll desolder this thing and measure it out of circuit when my new iron has arrivedThese multilayer pcb's are conducting soooo much head

author: Twoflower
author_rank: Frequent Contributor
timestamp: November 11, 2018, 04:45:29 pm
content: I would bet that this cap is not the problem. This parts are very high quality. I would look somewhere else for the problem of this card.

author: TheGenesis
author_rank: Contributor
timestamp: November 11, 2018, 05:41:19 pm
content: Mhmmm ... the card boots (only on HDMI ... DVI and DP are dead) and when the windows-driver tries to initialize the higher resolution, it flickers shortly and reverts to 640x480x16 with a driver error (driver tries this two times before giving up).I thought this could be a power problem, because the image is ok on lowres (safemode).I have found some burnt caps (the small ones) near the drMos chips, but everything else looks fine.Probed all fuses, shunt-resistors and drMos (vin against gnd), all coils and the 470's caps ... all of them having similar values. None of them are shortned or open ... coils are low on resistance, but i think thats normal.Also checked all phases against gnd ... no short at all.Probably there's a fault on a component under load.

author: Twoflower
author_rank: Frequent Contributor
timestamp: November 11, 2018, 06:02:28 pm
content: That the card runs in low res but not in higher resolution could also be a RAM issue. But the problems with the DVI and DP might indicate a different problem. But I'm lost here. Maybe there's VRAM test available you can boot from an USB-Stick to test the RAM.And you don't have any overclocking/undervolting active? I'm counting factory overclocked cards also as overclocked. Some cards have a switch to switch between overdrive/normal BIOS. Just thinking here.

author: TheGenesis
author_rank: Contributor
timestamp: November 11, 2018, 09:43:07 pm
content: VRam is not detected by GPU-Z, but this could be an issue to the exclamation in the driver tab.Is it possible, that these burnt bypass caps causing such errors?I have bought this card as "defect" and the previous owner gave me no info's on the cards history.Seems that dust has sometimes completly blockt the side of the pcb where the power connectors are attached. The fan on this side is only 50% spinning right now due to a clogged bearing.I'm afraid reflashing the bios right now ... if it fails the bios is will also be bricked

author: TheGenesis
author_rank: Contributor
timestamp: November 26, 2018, 08:53:29 am
content: Update ... after i replaced the burned caps (4 on the back and 10 on the top side) and reflowed the vrams, the card performs like new.Thanks to everyone for helping.