820-2915 shorted gpu

Chuck60

Member
Ok so I removed the gpu and i have no chime. I checked the tona resistor r7402 12.55v and it’s 91k. Ppvcore_s0_cpu ph1,2,3
.78-.9v PPVCORE_so_axg_L=.458v
Cpuimvp_boot1G=4.7v is this right ?
 

2informaticos

Administrator
Staff member
Why did you remove the GPU so fast?
Even shorted, disabling GPU for test is very easy on this board.

VCORE looks good now, but you still need to force iGPU.
Did you check USB activity?
 

Chuck60

Member
Someone had previously remove and mount it sideways I just removed it and placed correctly but it was shorted. So I took it off.. Yes blinking mouse and blinking usb stick
 
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Chuck60

Member
Ok.
1-What would be the right usb mouse solid light ? I just wanna know for next time.
2- Also after a newer gpu “2017” is swapped and the client wanted the underfill replaced I was gonna use Loctite 3513. Because High temp silicone smells Strong so I’m hoping 3513 is better. Do you have a product Suggestion that is better ?
3-the video memory was also reflowed because there’s flux and the underfill is removed here as well. Will this cause my current issue?
 
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2informaticos

Administrator
Staff member
As I said, you should try disabling GPU first.
You must get steady light on USB mouse and video with iGPU.
If not, you have another problem on the board.

I will not waste the time changing GPU on these boards.
Explain to the client, impossible to get real new chip; you've probably soldered a refurbished one now.
 

Chuck60

Member
Ok i was wrong it was booting I just had no chime. Weird thing is I just have no chime but the audio does work When it boot into OS X the audio works :/ . I’m not sure why I don’t get a chime I tried PRAM a few time and nothing. all I have left it to resolve no WiFi hardware installed and 1 usb isn’t working :/ thank You In advanced for any help. I’m gonna start at L3401
 

2informaticos

Administrator
Staff member
PRAM reset should bring chime back.
I remember someone else claimed about this issue last month.
However, chime matters so much?
 

Chuck60

Member
I’m not sure it’s not in me :/ I’m just trying to resolve all issues before it leaves so they have nothing to complain about. I found the usb issue it was d4600 along with 3 vias that I ran jumpers to. All I have left is the chime so if I solve it I will post it here so maybe it can help someone else. :) thanks a lot for your help
 

Chuck60

Member
ok I found something only there 4 caps I found 28ohm short. In diode I get .028v two are tantalum c6622 and c6632. The other two are ceramic. I was thinking that maybe that tantalum as they have a higher failed rate but at 5v I’m not sure which direction to go. At first I thought it was the chip but measurements I have around chip .489v to .520v and the gain test point measures .487 off u6630 but u6620 is cover with underfill so I couldn’t test all leads. What is your honest opinion? I’m still trying to recover chime :/ oh and oddly audio does still work but only after OS X boots :(
 
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Chuck60

Member
I replaced u6620 and got chime I really took my time protecting all the plastic and only burned just the upper corner of the sub connector :) I’m so glad that’s over
Thank you informatico for all your help
 
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