xbox360 trinity power issue

[sas67]

hi guys,i have a major problem with my trinity mobo
it wont power on at all now.it beeps but nothing else.when the problem first started i googled and most posts said power brick was going bad,so i bought another new power brick.
initially with new power brick it booted up first time,but never since
i have tested both power bricks on another xbox slim and both work
so my guess is motherboard issue,i have discussed this in length with "maseo" and he has spoken to people here and at c4eva and they think its issue with transformer on the mobo.
i should add,before its asked,this trinity was rgh'd but only to get dvdkey for ltu2 pcb on the d5s drive.
it has run fine for a year but alas now seems foobarred.
i have a multimeter so any ideas on places to check on mobo to find cause or eliminate from inquiries?
thanks lads

 

[BrockThunderjam]

Check the resistor at STDBY_CLK (point B) to make sure it's not damaged or lifted.

 

[sas67]

Check the resistor at STDBY_CLK (point B) to make sure it's not damaged or lifted.

the point where i soldered wire too during rgh for key?

 

[BrockThunderjam]

the point where i soldered wire too during rgh for key?

Yes. The symptom of damaging that resistor or lifting the pad where you solder to is a beep when you press power, and nothing else. Check for continuity between the pad (if it's still there) where you soldered to and the right side of the resistor the trace leads to. Then check the resistance of the resistor, should be ~33 ohm.

You should post some pictures of that area anyway.

 

[sas67]

sorry for delayed reply Brock,wifes been ill.
anyway the resistor and pad look ok,resistance is 33.2 ohms and got a continuity test and it beeps which is good,in a way
anything else you can think of mate?
as said in OP trinity was rgh'd but only to get to xell,for ltu2 pcb purposes
i read somewhere about removing resisotr on rf board?C5
any help would be most welcome

 

[BrockThunderjam]

It's hard to tell anything with your picture. It's very blurry. Could you please circle the points you measured for continuity? See below, this is what you should be checking.

 

[sas67]

That's where I probed for continuity

 

[Krafter]

You shouldn't be measuring continuity on those points. You need to read resistance. You should get ~33 ohms.

 

[BrockThunderjam]

So this console ran fine for a while and all of the sudden this started huh? Can you try applying a light amount of pressure to the southbridge and see if it boots?

 

[chase]

check R3B15 and make sure its 33 ohms .. then you need to check your standby voltages.. 5v, 3.3v and 1.8v

 

[stucknvegas]

After you can confirm R1-resistor and its trace is OK !!! do you have 3.3 stand by voltage at J23C header pin
You can try a different RF board --for me thats never the problem
That console worked for a year after the RGH to get keys
It could be south-bridge ..or Hana chip as well

 

[sas67]

thanks for your replies guys,
yes i can confirm R3B15 resistor reads 33ohm's and continuity tester beeps so its ok

http://prntscr.com/69ls1c

ive tested voltages on all 3 stby points,as in above pic
J23C im not getting any readings from
i did as you asked Brock and yes it powered up,flashing green light,but im presuming its because i havent got dvd drive and hdmi cable inserted
i powered it down and tested 3 more times and it powered up all 3 times without pressure on the southbridge!!
so tonight after work ill hook up drive and hdmi cable and test

 

[Antalpromille]

thanks for your replies guys,
yes i can confirm R3B15 resistor reads 33ohm's and continuity tester beeps so its ok

http://prntscr.com/69ls1c

ive tested voltages on all 3 stby points,as in above pic
J23C im not getting any readings from
i did as you asked Brock and yes it powered up,flashing green light,but im presuming its because i havent got dvd drive and hdmi cable inserted
i powered it down and tested 3 more times and it powered up all 3 times without pressure on the southbridge!!
so tonight after work ill hook up drive and hdmi cable and test

Sounds like your southbridge needs a reflow or a reball then.

 

[sas67]

hi guys,sorry for delayed reply.
since i powered on with pressure on the southbridge all has been ok.xbox powers up everytime
when i first connected hdmi to tv i had amessage appear onscreen.
should have really taken photo but didnt have phone to hand
it was about ventilation and system shutdown if memory serves me right
i havent rebuilt console as yet,just have it in chassis
ill monitor it before i fully re-assemble

 

[sas67]

gone down again,either doesnt power up or powers up then shuts down again.
would it be worth replacing paste on cpu or is it southbridge reball?

 

[Krafter]

My money is on the Southbridge. If your in the US then I suggest you get with nofeloniesyet for a reball.

 

[sas67]

im in uk unfortunately.anyone know of reputable people who could do this?