Gigabyte Brix Pro 4770R motherboard shorted! - Page 1
Forum section: electronics / repair

author: gamalot
author_rank: Super Contributor
timestamp: December 20, 2018, 07:30:52 am
content: This mini PC is powered by a common laptop style 20V/7A DC power adaptor. When I connect it to the mains, the power adaptor will enter the protection state and cut off it's output to PC.I measured the input resistance of the PC's power in jack, which was determined to be shorted. I also measured all the MLCCs on the motherboard, between 20V rail and ground, all their resistance values are less than 100 milliohms.Any suggestions? MLCCs, MOSFETs, or maybe DC-DC converters?

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 20, 2018, 11:39:06 am
content: heat gun? starting from input jack?

author: wraper
author_rank: Unknown
timestamp: December 20, 2018, 11:59:57 am
content: Look for TVS diode connected between 20V rail and GND.

author: gamalot
author_rank: Super Contributor
timestamp: December 20, 2018, 01:16:22 pm
content: Quote from: Mechatrommer on December 20, 2018, 11:39:06 amIt seems like the input jack is OK.

author: gamalot
author_rank: Super Contributor
timestamp: December 20, 2018, 01:17:15 pm
content: Quote from: wraper on December 20, 2018, 11:59:57 amI didn't find anything looks like TVS.

author: gamalot
author_rank: Super Contributor
timestamp: December 20, 2018, 01:18:18 pm
content: Damn it! I can't even get a capacitor off the motherboard, it must be red glue !!!

author: wraper
author_rank: Unknown
timestamp: December 20, 2018, 01:25:31 pm
content: Quote from: gamalot on December 20, 2018, 01:18:18 pmVery unlikely. Not used motherboards. Post photos of the PCB.TVS diode should look like this:

author: gamalot
author_rank: Super Contributor
timestamp: December 20, 2018, 01:35:59 pm
content: Quote from: wraper on December 20, 2018, 01:25:31 pmI know TVSs look like diodes, actually I have even checked all TO23 components.Pictures attached, sorry maybe they are not clear enough.

author: wraper
author_rank: Unknown
timestamp: December 20, 2018, 01:42:42 pm
content: Quote from: gamalot on December 20, 2018, 01:18:18 pmDo you mean black capacitor nearby connector? If it's sitting on 20V rail, quite possible it has gone short.

author: gamalot
author_rank: Super Contributor
timestamp: December 20, 2018, 01:46:54 pm
content: Quote from: wraper on December 20, 2018, 01:42:42 pmNo, I mean those size 0805 MLCC capacitors. Big black components are 330uf tantalum capacitors, maybe only rated at 2V, I guess.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 20, 2018, 02:06:12 pm
content: Quote from: gamalot on December 20, 2018, 01:16:22 pmnext? black ic and diode near it look interesting. the 2nd left diode? in the group of 4 also looks not so good.

author: gamalot
author_rank: Super Contributor
timestamp: December 20, 2018, 02:28:12 pm
content: Quote from: Mechatrommer on December 20, 2018, 02:06:12 pmThose things look like diode are actually low voltage tantalum capacitors.

author: gamalot
author_rank: Super Contributor
timestamp: December 20, 2018, 03:19:19 pm
content: Finally I decided to add 5A current to the motherboard, after a few seconds a DC-DC chip becomes very hot!

author: Rasz
author_rank: Super Contributor
timestamp: December 20, 2018, 03:50:27 pm
content: Quote from: gamalot on December 20, 2018, 01:18:18 pm8 or more layer pcb, hotair + preheater or you risk deforming/ripping pads offtake off TPS51363 and measure againI would also measure all the PL inductors to ground

author: gamalot
author_rank: Super Contributor
timestamp: December 21, 2018, 05:50:58 am
content: Quote from: Rasz on December 20, 2018, 03:50:27 pmThe trouble I am having now is that I don't have a preheater.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 21, 2018, 06:16:38 am
content: Quote from: gamalot on December 20, 2018, 03:19:19 pmcheck downstream for the short. or disconnect load if possible. and also check the dc dc if its "pwm"ing.. tool needed... oscilloscope..thats the reason i bought seek thermal