A1706 820-00239-A No LED External Only / No SSD

[Cire3]

A1706 820-00239-A No LED External Only / No SSD

No liquid damage found. No power a the nand. Boots to external screen only, then flashes folder.

U8203 Gets really hot.

PP3V3_S5 Pin 1 - 3.36V
PP3V3_S5 Pin 4 - 3.37
PP3V3_S4 Pin 6 - 0.19V

Best method to isolate PP3V3_S4 ?

 

[2informaticos]

"PP3V3_S4 Pin 6 - 0.19V"
Check it in diode mode.

 

[Cire3]

Pin 6 - 0.000 in diode.
Pin 6 to ground 0.5 Ohms

 

[2informaticos]

Low enough to use voltage injection method.
Start with 1V, no more than 4V.

 

[Cire3]

Gotcha, I'll report back !

 

[Cire3]

That was helpful, found short in cap C4205. Didn't take much at all. (Had to order)
U8203 cooled down

PP3V3_S4 Pin 6 3.36V now

However now, no display? Gonna poke around, but good progress !

 

[2informaticos]

Did you test USB activity and external video?
What is CPU core voltage behavior?

 

[Cire3]

Must have goofed something up. I do have video.

I have external video Via USB C. Still a flashing folder. Unit is running outside of chassis.

Sorry, also a first responder. So time on this has been sporadic at best this week.

 

[2informaticos]

So missing internal video?
In such case, check diode mode to ground at pins 1 & 3 of J8500.

Is the lifeboat connector (J9600) closed?

 

[Cire3]

Yes, checked J9600 is closed. Appears clean and connected.

unsure of internal video, board is out. Flashing folder on boot. Booted to disk utility, unable to see SSD.

J8500
Pin 1 : 0.314
pin 3 : 0.315

This unit they are really looking for the data.

 

[Cire3]

Trying to trace SSD Nand power. Schematic shows U5910. I see soldered pads, but missing ?

Doesn't look ripped off?

 

[2informaticos]

If U5920/30 also missing, then U5910 is not used.

 

[Cire3]

Well, I guess I have spares of those...lol yes, U5920/30 missing.

 

[2informaticos]

Then these chips are not used...

 

[Cire3]

Ok, back at it. Little fun fact.

PP5V_S4 is at 13v !
PP5V_S4 to PPBUS_G3H 0.7 Ohms

 

[2informaticos]

You may have lot of damage on the board now.

Replace U7600 and pray!
Be sure R/C7609 are both good; as their traces too.

 

[Cire3]

Trying to track down the data sheet for 58879D CSD55879Q3D = U7600

Not finding a whole lot. Ordered this as the closest I could find from Digi key

CSD87334Q3DT​