I killed my usb powered router by accidentally feeding it 12v..I want to save it - Page 1
Forum section: electronics / repair

author: bobbydazzler
author_rank: Regular Contributor
timestamp: March 19, 2023, 06:44:00 am
content: As the topic states I've killed my router via over voltage. When I apply usb power now there seems to be a short in the dc-dc converter right after the micro usb jack and it gets really hot really fast. I'm hoping I can desolder/disconnect the dc-dc power supply and feed 3.3v in via the serial port header and it might still work(I assume the dc-dc converter was outputting 3.3v because apparently the router runs fine with usb power down to 3v). Here's a photo of my router board, the dc-dc converter is in between the micro usb and usb port, I'm thinking I need to desolder the 5pin ic which I guess is controller the inductor? Anyone have any thoughts/ideas on what I need to do?

author: daisizhou
author_rank: Super Contributor
timestamp: March 19, 2023, 06:50:20 am
content: It is recommended that you try replacing the 5-pin chip.After attempting to unload the 5-pin chip, measure the circuit again for a short circuit fault

author: magic
author_rank: Super Contributor
timestamp: March 19, 2023, 07:20:27 am
content: Identify the buck converter. The board may be running on less than 3.3V and you could fry it (if it isn't fried already) by applying 3.3V.

author: DavidAlfa
author_rank: Super Contributor
timestamp: March 19, 2023, 08:07:46 am
content: Take a proper image of the DC converter.You might have been extremely lucky and the short be caused by a capacitor or diode, but I don't think so!

author: bobbydazzler
author_rank: Regular Contributor
timestamp: March 19, 2023, 08:18:03 am
content: Well I've desoldered the 5pin IC and it fixed the short and after supplying 3.3v to the serial port vcc/gnd pins the router works fine, I can connect fine to my 5ghz wifi access point lol even the full sized USB port still works if I also add the micro usb input power. Thanks everyone now need to bodge up a permanent 3.3v power supply. I wasn't able to identify the IC to make sure the output voltage was 3.3v but I think it's fine now anyway.

author: magic
author_rank: Super Contributor
timestamp: March 19, 2023, 08:46:59 am
content: Post a picture, maybe somebody will recognize this chip.I once fixed a device with a small switcher like that simply by replacing it with LM317, couldn't be assed to identify and repair it properly

author: bobbydazzler
author_rank: Regular Contributor
timestamp: March 19, 2023, 09:17:49 am
content: I couldn't read the writing on it before I desoldered it and now it's definitely unreadable after I dumped a giant solder blob on it to remove it, if I do apply I small internal 3.3v power supply to run off usb power I will probably use some AMS 1117's. The router's pulling 0.350ma on average so I think a AMS 1117 can handle that.

author: DavidAlfa
author_rank: Super Contributor
timestamp: March 19, 2023, 09:25:46 am
content: Just clean it thoroughly, some brushing with any solvent will work, marking is usually laser-engraved and won't go away.

author: Miti
author_rank: Super Contributor
timestamp: March 19, 2023, 10:04:17 am
content: The USB host must need 5V.

author: shapirus
author_rank: Super Contributor
timestamp: March 19, 2023, 10:09:58 am
content: Quote from: Miti on March 19, 2023, 10:04:17 amIts power pins are probably wired directly to the input jack's one.

author: jonpaul
author_rank: Super Contributor
timestamp: March 19, 2023, 10:28:06 am
content: get a new one $3

author: bobbydazzler
author_rank: Regular Contributor
timestamp: March 19, 2023, 11:07:40 am
content: I can't get a non blurry picture from my camera, I've looked with my magnifying glass and all I can read is FV9VG.. there might be something written after that I can't make out.

author: fzabkar
author_rank: Super Contributor
timestamp: March 19, 2023, 03:51:04 pm
content: The marking style looks like Silergy's, in which case the marking would be FVxyz (FV = part ID, x = year, y = week, z = lot number). Unfortunately, Silergy's datasheets are not publicly available.I think the best you can do is to trace the circuit and try to find a substitute.