xbox 360 blowing mosfet

[waldoalvarez00]

Hi Folks:

I have an xbox 360 that had a shorted USB pin. After unbending it and turning it on it came without video and red ring. I tried the towel trick and it came up with video. Then the power source led turned red and I heard a mosfet failing. I tested the mosfets and found the two 5v mosfets were shorted (they showed as two resistances on the tester). I replaced them but now the one closer to the CPU is shorting everytime I power it on. If I remove it it starts with red ring.

Any ideas of what could be failing? Maybe a shorted capacitor? What tests should I do?

Regards

[ReeceyBurger123]

What else have you checked for S/C in that area ?

[waldoalvarez00]

Originally Posted by ReeceyBurger123

What else have you checked for S/C in that area ?

I don't see short circuits in that area. I put the Meter in diode mode to test continuity and there are none with ground.

[momaka]

Post a picture of your board and tell us exactly what parts you think failed (i.e. Qxx, Cxx, etc.) and what you replaced them with.

Also, the towel "trick" is simply that - it is a crappy temporary repair at best, and usually does more damage than good. If you got an RROD with a secondary code typical of GPU failure, then do a reflow on the GPU. Here is a rather crude but fairly easy method:
http://www.badcaps.net/forum/showpos...3&postcount=15

Again, do NOT use oven or towel "tricks" - they are always done by people who don't know what they are doing. Spending a little bit of money to get decent tools (a heatgun and temperature probe) is a must if you want to do it properly, and especially if you intend to keep your 360 console working for as long as possible or fixing other 360 consoles.

[waldoalvarez00]

Ok I replaced those two with ones from another console, it got fairchild ones (both were damaged) so I putted two On semiconductor new ones (tested as good on the transistor tester) http://www.onsemi.com/PowerSolutions...o?id=NTD60N02R



You see the one closer to the CPU next to the small black capacitor blew two times. No smoke no holes no nothing. The fan tries to start for a second then it stops entirely. It gets damaged and shows as to resistors on the tester. Maybe the controller chip? Just wondering. I don't have oscilloscope to test.

Are you sure this gotta do with GPU reflow thing? That part of the circuit I think feeds USB and drives with 5V. Testpoints on all other parts give me 0v readings for RAM, CPU VRM and GPU VRM. Standby testpoints are the only ones good, 3.3v and 1.8v on the upper side of the board. No more voltage readings anywhere else.

I know it gets +12 v on the upper Mosfet base for a short while if I remove it and start the console. Then goes back to zero and give the three rings.

Yes I know towel trick is bad stuff. I just tried it to test it. I had no solder station then. Strange thing is it started for sure and I got video. Then it lost video but was still making sound (so yes maybe GPU reflow as you say is needed). After that trying to start it again it gave me sound, the Mosfet failed and the power brick turned the led red.

I think there are two things here. GPU problem and something else. I am looking to find that other problem and then jump into GPU reflow.

[momaka]

Sorry for the late reply. Finally have enough time to read through this thread.

Originally Posted by waldoalvarez00

You see the one closer to the CPU next to the small black capacitor blew two times. No smoke no holes no nothing. The fan tries to start for a second then it stops entirely. It gets damaged and shows as to resistors on the tester. Maybe the controller chip? Just wondering. I don't have oscilloscope to test.

Yes, that is one possibility.
Though it could also be a short-circuit on that rail (shorted ceramic cap, or some other connector you are missing out). To test that, remove the shorted MOSFET and measure resistance between one of the legs of that toroid inductor and ground. Use the lowest resistance scale on your multimeter (that's usually 200 Ohms on manual meters). Report back what you get.

If there is a short-circuit, that could be the reason why your MOSFET keeps blowing. But if not, then maybe it is the buck controller for that rail that is bad.

Originally Posted by waldoalvarez00

Are you sure this gotta do with GPU reflow thing? That part of the circuit I think feeds USB and drives with 5V.

No. You are correct here.

Originally Posted by waldoalvarez00

Testpoints on all other parts give me 0v readings for RAM, CPU VRM and GPU VRM. Standby testpoints are the only ones good, 3.3v and 1.8v on the upper side of the board. No more voltage readings anywhere else.

That's because the Xbox PSU is shutting down due to an overload or hard short-circuit on the 12V rail from that MOSFET you mentioned above failing.

Originally Posted by waldoalvarez00

I know it gets +12 v on the upper Mosfet base for a short while if I remove it and start the console. Then goes back to zero and give the three rings.

That can happen if the motherboard is checking for all of the voltages, and when one is missing, it shuts down the PSU.

Originally Posted by waldoalvarez00

I think there are two things here. GPU problem and something else. I am looking to find that other problem and then jump into GPU reflow.

I concur.
That's how I would proceed with the troubleshooting as well.

[stj]

when it shorted, did all 3 pins short together?
if yes, then whatever is driving the gate pin may be damaged.

[waldoalvarez00]

Originally Posted by stj

when it shorted, did all 3 pins short together?
if yes, then whatever is driving the gate pin may be damaged.

Not really sure. They show resistances in all the damaged Mosfets so yes could be the case. So what is driving the gate should be connected to a resistance. I have a 360 schematic, I attached it. I think is PAGE_TITLE=VREGS, V1P8 AND V5P0. So seems to me that part of the circuit is driven by the NCP5425 (http://www.onsemi.com/PowerSolutions....do?id=NCP5425) through those resistances R5F5 and R5F6.

[stj]

Originally Posted by waldoalvarez00

Not really sure. They show resistances in all the damaged Mosfets so yes could be the case. So what is driving the gate should be connected to a resistance. I have a 360 schematic, I attached it. I think is PAGE_TITLE=VREGS, V1P8 AND V5P0. So seems to me that part of the circuit is driven by the NCP5425 (http://www.onsemi.com/PowerSolutions....do?id=NCP5425) through those resistances R5F5 and R5F6.

do you have schem's for other xbox boards?

[waldoalvarez00]

Originally Posted by stj

do you have schem's for other xbox boards?

I didn't but found them here is for Falcon. Enjoy

[keeney123]

So they have a phase Lock loop on the power supply. They must have a problem with the frequency of the power supply drifting?

[stj]

Originally Posted by waldoalvarez00

I didn't but found them here is for Falcon. Enjoy

nice

[waldoalvarez00]

Sometimes in SMPW I get the Mosfets blown when the feedback is damaged as they run on superhigh duty cycle. Also with shorts somewhere else as the tension output is so low the duty cycle is way too high for the Mosfet.

[waldoalvarez00]

I noticed this model is not the same exactly as the one in the schematic (Xenon), it is a Falcon board. It has no SMD resistors coming from the controller to the gates and has this controller http://www.analog.com/en/products/po...s/adp1823.html

I tried another thing. I removed the USB ports since they were bent anyways and just in case they had some shorts. I have a Xenon board bent and broken picked from the garbage, with some stuff missing but the USB ports and many things are ok.

So putted another mosfet and took the risk to power it on. Well this time it holded and didn't got damaged but the power brick is sensing something as the console spins the fans for a second and then the power brick turns the led red activating sort of an overcurrent protection mechanism.

[momaka]

Originally Posted by waldoalvarez00

So putted another mosfet and took the risk to power it on. Well this time it holded and didn't got damaged but the power brick is sensing something as the console spins the fans for a second and then the power brick turns the led red activating sort of an overcurrent protection mechanism.

That means there is still a short-circuit somewhere. I would bet that 5V rail again. Just because the MOSFET there is no longer blowing doesn't mean the controller is working right. It could be that the controller is trying to turn on both the lower and upper MOSFETs for that rail, causing a temporary short-circuit and thus shutting the PSU down.

Originally Posted by waldoalvarez00

Someone suggest me in another forum to change the controller chip same as stj. Let's see how I can get one of those new chips.

Which controller is that? I might have it on a spare junk 360 motherboard.

Originally Posted by waldoalvarez00

BTW I was thinking in this case since I don't have the chip around now. Just inject those 5V from an ATX PSU in the electrolitic capacitor pins, removing the FETs to isolate and see what happens. Problem I think is the common ground.

Excellent!
I've done that before on TV board power supplies, and I can tell you that this method works. But definitely do remove the FETs and even the toroid inductor before doing that. Better yet, first check the resistance on that rail with respect to ground as I suggested in my above post. If you have a dead short-circuit, even your ATX PSU will not like it.

As far as common ground: some Xbox 360 PSUs are grounded and others aren't. But either way, just connect the ground of your ATX PSU to the ground of the Xbox 360 motherboard and it will not be fine.

Originally Posted by waldoalvarez00

No no, CPU and/or GPU doesn't feeds from that. One side is 5v for USB + Drives (i think southbridge too). I saw what seemed to be like 3 regulators feeding from there too. The other side of the chip is for RAM. I think is 1.8v, gotta check this again.

Here's a diagram I made a long while back of the voltage rails on the Falcon board:
http://www.badcaps.net/forum/attachm...1&d=1461040574

These voltage rails will be quite similar on the Xenon, Zephyr, and Jasper as well, so you can still use the above diagram as a general guide.

[diif]

Here's the Xenon stj

[stj]

Originally Posted by diif

Here's the Xenon stj

that was posted earlier in the thread.

[keeney123]

It would appear that the Phase Lock loop control is on page 50 at this IU7U1

[waldoalvarez00]

Originally Posted by keeney123

It would appear that the Phase Lock loop control is on page 50 at this IU7U1

Just a buck converter for the CPU. It just lowers the 12v from input to the VID specified by the CPU.

[keeney123]

So why is is listed as phase 1, phase 2, phase 3? You will also notice the output looks back to the input through the V_CPUCORE as a reference. I have not look up the IC, but it would seem to me that the different phases are being sent up by what is being feed back form the V_CPUCORE and this is what is causing when the phases are sinking.