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[MadMaxGR]

Check the MOSFETs with a multimeter. I think RDC has more details about how many V they must be etc.

[Murkonem333]

This thread seems old.. but its the closest one i found by searching on google that resembles my problem.

ok so.. i have 2 broken xboxs.. they both worked fine and then both got red ring.. one just sat around and i did the xclamp fix.. well after about a month or so it got red ring again.. maybe this has to do with me not really knowing that much about doing the xclamp fix..

anyway.. after this second time fixing it i go to hook it up and i have nothing.. no power whatsoever.. and the light on the power block is orange. so i hook up the other and it still has red ring.. i take it apart.. do the fix and then plug it up and have the exact same problem as the other one..

i know that its not the power block because i have a 3rd xbox that it works fine with.. but somehow.. when all i did was do the xclamp fix.. did not touch anything else.. both xboxs had the same problem at the same time..

there are no scratches or otherwise obvious damage to the motherboard. what could cause this when i have did no modifications or anything to it?

please and thank you to anyone that can help
i would appreciate it more than you know..

[PRiME2008]

Hello, I am going to presume a dead south-bridge but am hopeful some people have a couple more tricks I can try as I have the same issue as you as per mention in other thread.

If in the end the southbridge is fried then is only good for parts but it be nice exhaust all options first at getting the bastards to power up.

Heres hoping some smart fellas have some suggestions.

[MadMaxGR]

Your x-clamp fix must short out somewhere. Check if your heatsinks are tighten too much and touch capacitors. Just go thru any mod you have made and look for shorts.

[PRiME2008]

This is a possibility however the console didn't work even with Xclamps on, I removed those and just put in the bolts and does same thing. There also not over tightened, worth a second look anyway. Was hoping someone could suggest a series of resistors etc I could test, I have checked the 3.3, 1.8v ones they seem good.

[wilgo45]

Besides those Mosfets that handle power regulation, I have found powering capacitors and Inductor coils that are not working.

Currently I am working on a NO Power board.  It has two blown Inductor coils.  The bubbling on the tower is evident.  This unit will not hold standby power.

So look around your Mobo.  Look around for damage or browning in an area.  Get a meter and test things.  Test your Mosfest, Capacitors and Coils.

Don't worry about the RF module yet - focus on the Mobo

And don't always presume a Dead Southbridge.  I've usually found another issue to the No power.

Also check all your USB ports for damaged prongs.  They can cause a powering problem

[wang_chung]

what does it mean if you have 3.3 at u5b1, and 0v at u5b2 and u5b2 gets REALLY hot after about 20 seconds? i have tried replacing it with the same part off a xenon board i have (same part number too 17-18g)

according to the xenon board diagram online, u5b2 gets it's input voltage from c5b5 capacitor. well i can't find it anywhere on this board, unless the falcon's don't have the same cap feeding it.

[avenging robi]

hi i no this post is old but i need some help if possible as i love playing my 360 . im new to fixing 360s and was working on my own it was working perfectly and i got rrod so i loosened the x clamps and it worked but then it over heated to i tightend it and put it on the metal casing to boot it up it showed the green light and after 5 mins went to rrod then i turned it off botted it and it buzzed and smoked slightley from the bottom i turend it off and it was soldered to the metal casing  i pulled it off and now it wont boot the psu turns red straight away i have tried many psu and all the same one off the pins on the coil is shorter than the others could this be my problem if it helps i have a 2nd gen mother board and heat sinks its a hdmi xbox

[Roden]

Hi my friends, i wonder if you can help me, i stumbled across this thread  and is identical to i problem i have.

http://forums.xbox-s...o...539761&st=0

I fitted a cygnos to my falcon 360, exploitable dash 7371 and cb

All went well, i dumped my flash 3 times, programed the cygnos, all good, i went of to have some tea, when i got back my box was dead, will not power on, psu stays orange.

I noticed it was quite hot, even though it was not on, so i stripped it down again checked all the wiring all is good.

I noticed that one of the components you mentioned : Voltage Regulator U5B1 (3.3V) , is getting red hot, so i can only asume this is short, or something else is overloading it.

I am really gutted as i was 2 steps from having a jtag box, i have no idea what happened or caused it, i was wondering if you could shed some light on what to test and where to look, if its fixable or not.

Hope to hear from you, thanks, Jason.

[UnitedStatesRanger]

hey guys my psu sparked and no longer works (no lights showing) I went ahead and replaced the psu with the same model type, however now when I try turning the 360 on the psu and 360 flashes green for a split second than goes back to yellow (no red at all) same goes with the fans after a split second they shut off. I did the xclamp and I notice that it did turn on leaving a 0001 code error than after I shut if off it didn't work any longer and atm I'm at a lost right now cause its not powering on.

Any tips on what could it be?

ps. I took a picture of where I'm hearing a rattling sound and circled in yellow.
http://i35.tinypic.com/eupk7k.jpg

could this be the problem?

[syntaxerror329]

QUOTE(UnitedStatesRanger @ Aug 14 2010, 03:49 PM)

hey guys my psu sparked and no longer works (no lights showing) I went ahead and replaced the psu with the same model type, however now when I try turning the 360 on the psu and 360 flashes green for a split second than goes back to yellow (no red at all) same goes with the fans after a split second they shut off. I did the xclamp and I notice that it did turn on leaving a 0001 code error than after I shut if off it didn't work any longer and atm I'm at a lost right now cause its not powering on.

Any tips on what could it be?

ps. I took a picture of where I'm hearing a rattling sound and circled in yellow.
http://i35.tinypic.com/eupk7k.jpg

could this be the problem?

LOL, nope that is the tilt switch. It has a ball bearing in it the signals the southbridge as to the orientation of the 360 so that the ring of light knows what quadrant is player 1.

Try this. Power up a 360. Sync a controller. Move the 360 from vertical to horizontal and you will see the ROL will change.

Anyhow, i wqas just trolling this thread. I have a 360 that wont power on at all. Was loking for some tips. I wish i had RDC sitting here with me.

[psp_ps2_2005]

QUOTE(G0t M4xx 21 @ Aug 20 2006, 07:20 PM)

Chris, I replied to your PM on this, but to spread knowledge on the scene, I will post basically what I said in my PM (a little bit more detailed):

If the PSU is confirmed working, it is either something wrong with the microcontroller in the southbridge that controls the power on sequence, the linear regulator that powers it and/or the ROL board, or a short in the 5V standby (blown capacitor, transistor, etc).

The easy way to determine which one of these is the problem is to look at the light on the PSU, if when you plug it into the 360 it turns red briefly (or stays red), there is a short on the standby power (If the short was on the switched supply, the 360 would power up then flash 3 red lights with error 0001 or 0002, or power up for a split second then shut itself off). Also measuring the resistance from 5VSB to ground is a pretty sure fire way to tell

If the 5V standby power is NOT shorted, then the issue is either in the power button on the RF board (easily tested by powering up the box via another method), the southbridge, the the voltage regulator supplying it.

The two regualtors are U5B1 (3.3V) and U5B2 (1.8V). They are located on the top of the motherboard near the back, jsut to the left of the large screw hole in the center of the motherboard (near the fans). The large tab opposite the 2 smaller pins is the output of each regulator, so they should measure 3.3v and 1.8v respectively when the 360 is in standby (off but plugged in).

If those measure ok, then I'd say the southbridge is dead (that motherboard is nothing but a nice paperweight)

i have had the same situation with a dead southbridge,,and swapped it by someone else from another mobo..
the system now is ok and starting up once pressing the power button but  with 3rlod,,i also swapped the gpu but still the same 3rlod....

has the southbridge married with the cpu and could not be replaced??

[hangover]

I have a xenon that wont power up, it was working fine before i replaced the thermal paste with AS5 and put the x clamps back on. When i plug it in and power with rol i get no light change on the psu- it stays orange , i checked the usb ports for damage and cant find anything else that would cause this ?