A2338 820-02020

[silver60618]

Hi I am working on A2338 logicboard with liquid spill damage around LVDS and CR638

Im getting 20v, .05-.40 amp draw on amp meter with boot loop

Im getting a heat signature on U0500 (what is this chip? I cannot find it anywhere, do any different board have this?
(Schematic says SEP EEPROM). reflowed with no difference

L77D0 .~0.27 (should be .49 based on repair wiki)

Any help on where I can look?

 

[2informaticos]

First of all, welcome to the forum!

"boot loop"
Do you get Apple logo and restarts?
Test with external monitor, disconnecting internal LCD assembly.

 

[silver60618]

Hi, no display, no apple logo. Sorry I didnt mean boot loops, amp meter loops 20v .05-.45 amps then amp meter reboots on both ports

 

[2informaticos]

Remove F5200 and check if you get steady voltage at C5250.

 

[silver60618]

F5200 (before removal) 12.07v
C5250 (after removal of F5200) 12.35v steady

 

[2informaticos]

"F5200 (before removal) 12.07v"
Steady, doesn't pulse in the rythm of USB-C ports?

 

[silver60618]

When amp meter reboots, F5200 goes down to 11.96v then back to 12.07v

Any idea of function of U0500?

 

[2informaticos]

U0500 stores some CPU informations.

You still didn't clarify if C5250 fluctuates, or not; with F5200 removed.

 

[silver60618]

with F5200 removed. Amp meter stuck at 5v, amp meter no longer loops
C5250 steady 12.35 v with F5200 removed, same behavior with fuse pad

 

[2informaticos]

So fluctuation is caused by something connected after F5200.
You may have a problem with a secondary power rail.
Check diode mode to ground on these rails.
Start with 3V8_AON, 3V3/5V_S2, etc...