Xbox One X 3.3v Short - Page 1
Forum section: electronics / repair

author: ajp8868
author_rank: Regular Contributor
timestamp: June 28, 2020, 06:22:48 pm
content: Hi All,Looking for some help/advice on trying to fix an Xbox one X motherboard which seems to have a 3.3v short to ground. The symptoms are quite common, it turns on for a second then goes off instantly.I've checked a number of points on the board and it seems there may be a short somewhere but locating that seems to be very difficult. Does anybody have any advice on how to locate a short without removing every component it could be?I'm also looking to see if anybody could identify this component attachedas I've broken it when removing (my hot air station doesn't seem to be hot enough)... The only marking on it is GEH which I can't find any info for!Many thanks!

author: fzabkar
author_rank: Super Contributor
timestamp: June 28, 2020, 08:55:53 pm
content: AP2127-ADJTRG1, Diodes Inc, 300mA, 2.5V - 6Vin, HIGH SPEED, EXTREMELY LOW NOISE CMOS LDO REGULATOR, marking GEH, SOT-23-5:https://www.diodes.com/assets/Datasheets/AP2127.pdf

author: ajp8868
author_rank: Regular Contributor
timestamp: June 29, 2020, 02:28:58 pm
content: Ah brilliant thank you! Don't suppose you have any advice as to why these are so hard to remove with a hot air rework station? Can't seem to melt the solder..

author: TheMG
author_rank: Frequent Contributor
timestamp: June 30, 2020, 04:27:14 am
content: It's probably sitting on large power/ground planes in the inner layers of the PCB, through all those vias.Pre-heating the PCB can help a lot by reducing how much heat is being sucked in to those planes.

author: ajp8868
author_rank: Regular Contributor
timestamp: June 30, 2020, 11:19:29 am
content: Makes sense, thank you for the advice.Sorry to ask so much but do you have any advice on what components to check first for a short to ground? I've checked some MOSFETs and voltage regulators which seem to be behaving normally and when removed the short is still there.Is it likely that it could be one of the tiny smd capacitors between ground and the 3.3v rail or do these very rarely cause issues?

author: TheMG
author_rank: Frequent Contributor
timestamp: June 30, 2020, 06:35:18 pm
content: The technique I use to find a shorted component on a rail that has a lot of components on it is to carefully apply current from a bench power supply to the rail. Start low and see if any component gets warm. If nothing then give it a little bit more current, keep going and eventually the offending component will usually start to heat up as long as it's not a total dead short (much less than 0.1 ohms).It help to have an IR camera but obviously not something everyone can afford. I use my fingers or some isopropyl alcohol on a cotton swab. The alcohol will evaporate noticeably quicker from a hot component.

author: ajp8868
author_rank: Regular Contributor
timestamp: June 30, 2020, 07:43:17 pm
content: Thanks so much TheMG, found the location of the short (sort of)It seems that the whole area around the chip in picture 1 is heating up.. could it be this chip or components around it?I've pictured the other side of the board too where it heats up, wondering if it might be another layer at fault?

author: ajp8868
author_rank: Regular Contributor
timestamp: June 30, 2020, 07:46:10 pm
content: Other side of the board (images are too large)

author: fzabkar
author_rank: Super Contributor
timestamp: June 30, 2020, 08:20:52 pm
content: Have you checked whether any of the ceramic capacitors are warming up? They are a common problem.This is the datasheet for the MP2853:https://www.monolithicpower.cn/cn/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/MP2853/

author: ajp8868
author_rank: Regular Contributor
timestamp: June 30, 2020, 09:08:54 pm
content: It's quite hard to tell as the whole area seems to get warm, think I might need to get hold of a thermal camera.. anybody in the Teesside area hiring them out?I guess the easiest thing to do from this point would be to de-solder a few?Thanks for the datasheet, that's some light reading for later lol

author: fzabkar
author_rank: Super Contributor
timestamp: June 30, 2020, 09:34:41 pm
content: I've never used one, but what about an IR thermometer?https://www.drivestar.biz/index.php?main_page=product_info&products_id=1038&zenid=v2dch9v76so2ef637gb827cv84

author: ajp8868
author_rank: Regular Contributor
timestamp: June 30, 2020, 09:41:03 pm
content: I think my work has one I might be able to borrow actually. Will give it a go!There's no real way to test these caps without removing is there?

author: fzabkar
author_rank: Super Contributor
timestamp: June 30, 2020, 09:44:17 pm
content: I always end up removing any suspect caps, but there are probably techs who know a better way.

author: ajp8868
author_rank: Regular Contributor
timestamp: June 30, 2020, 09:52:24 pm
content: Just waiting on some flux to see if I can actually remove anything so will try again tomorrow and see if I get anywhere. Thanks again!

author: langwadt
author_rank: Super Contributor
timestamp: June 30, 2020, 10:24:08 pm
content: Quote from: ajp8868 on June 30, 2020, 09:08:54 pmthe Luis Rossmann trick is to pour on some alcohol and see where it evaporates first

author: TheMG
author_rank: Frequent Contributor
timestamp: July 01, 2020, 12:08:57 am
content: That IC, MP2853, is a voltage regulator controller for the switching regulators presumably providing power to the CPU. The chip itself doesn't handle much power, it's just a controller for the actual switching regulator ICs.Per the datasheet, this IC appears to have a ground pad underneath that's soldered to the ground plane of the PCB, that's probably why the whole area is heating up.https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/MP2853/document_id/6613/Any other ICs or transistors in the vicinity also getting warm?

author: ajp8868
author_rank: Regular Contributor
timestamp: July 01, 2020, 08:37:48 am
content: Well I can't feel anything specific heating up. But I've noticed that when I put positive lead on the point circled in blue the CPU heats up, where as when I put voltage to the point circled in red, that other area around that other chip heats up.Could it be a CPU issue?

author: TheMG
author_rank: Frequent Contributor
timestamp: July 01, 2020, 02:07:52 pm
content: The point circled in blue I don't think is on the 3.3V rail, that looks like the output of the switching regulators going to the GPU chip, which is normally going to be much less than 3.3V (usually in the range of 1-2V).

author: ajp8868
author_rank: Regular Contributor
timestamp: July 01, 2020, 02:27:11 pm
content: Oh really? In that case it seems there's a short on that rail too, and it's the graphics chip that gets hot.. would that mean it's quite likely the GPU is knackered or at least shorted?

author: grumpydoc
author_rank: Super Contributor
timestamp: July 01, 2020, 04:01:39 pm
content: Inject a low voltage - max 1.0V into the 3.3V rail from a current limited PSU then- see what gets hot, pay particular attention to ceramic caps- try Rossmann's alcohol trick- probe the 3.3V rail starting at the PSU, as you work towards the short the voltage will drop (really need at least a 20,000 count DMM), if the voltage stops dropping you are moving away from the short.- if you can get hold of a thermal camera by all means try to see if you can identify the hotspot.

author: ajp8868
author_rank: Regular Contributor
timestamp: July 01, 2020, 06:24:03 pm
content: Thanks for that, really tried to narrow it down with all 3 techniques but so far all I see is that chip and the area surrounding it getting hot.I don't think my MM is good enough to detect the tiny voltages you're referring to but as far as I can tell it's getting to 0.1 near that chip and that's the lowest reference voltage.I was going to try removing it to find out if the short was fixed but I cannot for the life of me remove anything with hot air, doesn't even seem to make the solder soft. Do I need flux paste?

author: cheeseit
author_rank: Regular Contributor
timestamp: July 01, 2020, 06:37:15 pm
content: Which hot air station is it and what temperature is it set to?

author: ajp8868
author_rank: Regular Contributor
timestamp: July 01, 2020, 07:13:01 pm
content: It's a WEP 853D and I've tried it on all sorts of temperatures right up to (what it says is) 896c. Heated up the whole board first too but nothing comes off..

author: cheeseit
author_rank: Regular Contributor
timestamp: July 01, 2020, 08:22:50 pm
content: It's secondary to your problem with the Xbox but it's critical for fixing it. Something must be wrong with that hot air station, it should be able to melt the solder. Do you have a suitable thermocouple for your MM? If so, check the temperature of the hot air. If not, see if you can get hold of that IR thermometer or buy one, they cost next to nothing.Check a few videos on using hot air, just to see if you've got the technique down and don't cook the board in the process.

author: ajp8868
author_rank: Regular Contributor
timestamp: July 01, 2020, 08:55:20 pm
content: Just bought an IR thermometer, it'll come in handy more than once I bet. The gun does get very hot so I'm surprised it's not melting the solder, seems like I might end up having to fix that firstSo I've been doing a little more investigation on the parts that are shorted and it seems that nothing around the AP2127 chip is shorted. However, everything on the left hand side of the chip, towards the CPU is shorted to ground. Is it likely that the CPU is fried?I've also come across a component labelled FB2 which looks a little damaged, does anybody know what this is?

author: grumpydoc
author_rank: Super Contributor
timestamp: July 01, 2020, 09:36:04 pm
content: Quote from: ajp8868 on July 01, 2020, 08:55:20 pmSMD ferrite bead

author: ajp8868
author_rank: Regular Contributor
timestamp: July 01, 2020, 09:46:57 pm
content: Thank you. Looks like these should have some resistance?

author: grumpydoc
author_rank: Super Contributor
timestamp: July 02, 2020, 03:28:04 pm
content: Assuming that itisa ferrite bead it should be low resistanceThere's some info including a diagram showing how they are constructed here - I assume it is the same sort of thing.https://www.viking.com.tw/en/category/EMI-Bead-CBM-Series/Inductor-CBM.html

author: ajp8868
author_rank: Regular Contributor
timestamp: July 02, 2020, 10:00:33 pm
content: It would make sense, looks like one and is labelled FBNot had chance to look at the Xbox tonight but I'm going to focus on trying to trace the path from the MP2853 to the CPU as it seems to me that if that heats up first it must be shorting close to that. The four pins (VOSEN1, VORTN1, and 2) are all shorted to ground but the rest of the pins are fine.So is this chip only heating up because of the large ground pad or could it be shorted internally?

author: ajp8868
author_rank: Regular Contributor
timestamp: July 03, 2020, 04:14:37 pm
content: I think I may be at a loss with this board, both VORSEN pins on MP2853 as well the VDD33 input rail are shorted to ground.The only things warming up are the CPU area, and MP2853 and nothing gets particularly hot (not even enough to evaporate alcohol quick enough to notice)Can't seem to remove anything, so I'd probably need a preheater.Anybody have any more ideas before it goes in the bin?

author: ajp8868
author_rank: Regular Contributor
timestamp: July 03, 2020, 10:48:11 pm
content: Does anybody know if it's possible to separate the sections of the motherboard by removing a couple of components?