820-00875-a - a1708 - frying SSD'S

[Anterweb]

Apologies for any confusion. Yes it was shorted to ground, the resistor appeared to be fried and the short to ground was gone once it was removed from the board. What can I replace it with as I'm struggling to find the correct part number

 

[2informaticos]

I was thinking R5515 was stil in place; it was completely damaged?
The bypass must connect all 4 pins together.

 

[Anterweb]

Yes R5515 was dead, ( It defiantly appeared that way and if by chance it wasn't it sure as shit is now )

Ill try the bypass on it tomorrow but would like to replace it, What part can I replace it with as I can not find the part number?

 

[2informaticos]

Not easy to find: original is 0.003 ohm (3 miliohm).
Is I(current) sense resistor, with special Kelvin lines connection.
2-5 miliohm resistor in same format should work.

 

[Anterweb]

Bypass wires now on R5515 and No shorts to ground and I am getting 3.3v and 3.3v on Pin 56 of ssd connector.

But it still wont boot now, still getting no display and touchpad working for 10 seconds then not for 5 seconds then working for 10 and so on.

could this be in any way related to removing 8600 we did a couple of days back? this is still removed so I get no13v at pin 1.

 

[2informaticos]

"L8600 back in place and L8602 removed, now getting 0v on pin 1 and 3.31v on pin 56.
Disk utility can see the NVME drive"
So, is not related...

 

[Anterweb]

OK that's a good point.
I'm at a loss now ,I still have no screen turning on and what seems like it powering up for 10 seconds then off for 5 seconds then repeating. after a couple of minutes of this I can feel the cpu heat sink getting warm so it has some kind of fight left in it.

Is there anything else I can try or do I have to admit defeat now and give up on this one?

 

[2informaticos]

Check what happens starting in SMC bypass mode.

 

[Anterweb]

No change, same power on for 10 off for 5 seconds cycle

 

[2informaticos]

PPBUS_G3H and 3V3_G3H stable?
L7210/20 voltage appears in these 10s?

 

[Anterweb]

PPBUS_G3H = present and stable
3V3_G3H = present and stable

L7210 and L7220 both Start at 1.5v then instantly drop to 0.0v

 

[2informaticos]

Something went wrong when made the short on the board.
The board may be useless now; good for scrap at least.

 

[Anterweb]

I presume I shouldn't get short to ground on both sides of L7210 and L7220, is it worth injecting voltage to see if anything stands out? or should I just throw in the towel?

 

[2informaticos]

L7210/20 have very low resistance to ground as normal.

 

[Anterweb]

So checking the power rails tonight before giving up I notice PP3v3_S4 is missing, could it be this causing the power cycle no boot? Best way to check diagnsoe? I'm tempted to inject voltage?