Trinity power supply instant Red dot on power on

[SlothGSR]

Hi,

I have a Slim Trinity that I'm attempting to fix. MS seal was intact, So console was never opened. What happens is when I hit power button, the Power supply kicks into red dot. So I opened it up and saw nothing out of place. I checked visually all USB, LAN, AV ports for shorts and couldn't see anything. I took everything off the MB and pulled it out of the cage and attempted to turn on with MS media remote. Same thing, Red Dot on power supply. So i read up it has something to do with the 5vSB rail. I'm no expert when it comes to electronics, but trying my best here to learn as I go. I found a picture showing all the Stand by voltages and tested them.

here is the picture I used for refference:http://xbox-experts.com/pics/xbox_36...ources_top.jpg

and here are my results: I circled the ones that are not normal.

I've read that it could be Mosfets causing this issue. I'm still figuring out how to check which ones it might be. If anyone can help me, its much appreciated. Thanks

 

[Utmad]

I do not think you can check mosfets when connected i am sure they have to be removed, normally you can see bubbling on the surface of them though if faulty

 

[SlothGSR]

I do not think you can check mosfets when connected i am sure they have to be removed, normally you can see bubbling on the surface of them though if faulty

I don't see any problems visually with any of them. I'm wondering if anyone else that has had this problem could steer me in the right direction, as to which one(s) to closer inspect.


UPDATE: After testing on a good trinity, using the picture of the voltages. All the yellow 12v show up as .59 all 7 points.

then on my dead board, I'm not getting anything.

mosfets U5B1 and U5A1 are both getting same results on good and bad boards.

Besides the 12v mosfet points, the only difference between good board and bad board is with the 2 GND points on the standby on the right.

 

[pengekcs]

I know it's too obvious but have you tried the power supply with an other xbox or tried an other power supply with your xbox? I have seen the power supply killing itself, maybe that's it?

 

[Martin C]

Yes, you have a short on the 12v rail.

So possibly one of your 12v FETs is damaged.

 

[SlothGSR]

Yes, you have a short on the 12v rail.

So possibly one of your 12v FETs is damaged.

Ok, So which mosfet should i start to replace first, Is there even an order that it flows? I'm getting 0V at all 7 12V points, So that tells me its probably something before the mosfets?? I might be out of my league trying to fix this, but I like the challenge. Anyone have a diagram of the 12V Rail? Thanks

 

[mr2000jp]

i had this problem with 2 trinity boards , i noticed this happens quite some times with trinity motherboards , and this happens with the ones used for some time ,i think some thing gets too hot and gets burnt by the usage time , i think it might be a design flaw , any way i did thorough tests on one of the boards and found that some mosfet transistors are faulty like martin c said , the problem with those most of the time is that not one mosfet gets damaged ,every module or what ever you can call it is made out of a power controller (pwm) and 2 or 4 mosfet transistors , since they are connected in a series if one gets damaged or the power controller chip, you have to replace the whole circuit , in my case it was this in the picture , its always best to replace the whole circuit as a whole because they would probably all be defect , and if you replaced one mosfet the new one will be burnt immediately if the power controller was defect ,