[help]Imac 820-2641 TOTALLY DEAD; NO LED

[phantom]

hi! i don't know the history of this computer...it is completely dead, no status led at all..i already tried another good power supply without luck:.....any hint?

thanks

 

[2informaticos]

Do you get 3V3_S5 (L7710)?

 

[phantom]

no voltage at all, line not shorted...

compared with another board

 

[2informaticos]

Post U7700 basic voltages.

 

[phantom]

U7700: 17, 18, 5, 4, 24, 12.

12v, 5v, 5v, 5v, 0,3v, 0v

i have 0v on pin 1,2,14 of u6900 0,3 on pin 3

 

[2informaticos]

Check R7722/23 and their traces.

 

[phantom]

i've done a mistake: i have 3,8v on pin 12

 

[2informaticos]

Then 3V3_S5 must be present at L7710.

 

[phantom]

i confirm i have 0v on both sides of l7710

 

[phantom]

i recheck all voltage and i confirm them
U7700: 17, 18, 5, 4, 24, 12.

12v, 5v, 5v, 5v, 0,3v, 3,9v


i havent voltage on l7710....

 

[2informaticos]

Bad chip, solders, or adjacent components...

 

[phantom]

u7700 changed: no luck

 

[phantom]

how is it possible???'

 

[phantom]

Then 3V3_S5 must be present at L7710.

from where is generated 3v3_s5?i'm pretty sure that u7700 is soldered good

i confirm that i have 0,3 on pin 12

 

[2informaticos]

Be aware, is not easy to solder chips on iMac boards; you've mentioned such a problem on the other board in fact.
Apply first leaded solder on the pads; chip and board too.

 

[phantom]

i've resoldered another u7700 and i have had for a moment the first led.