A1534 820-00244 no boot

[DCSTechs]

Hi, new to the forum and have been reading some of the posts on the A1534 and not feeling good about getting this one. Device had battery changed by another tech and now will not power up. Below are the voltage measurements. PM_SLP_S4_L = 0 which I think is due to PM_RSMRST_L being at 61mv. R7810 resistance measures fine and did not find anything out of the ordinary with diode mode. Tracing back on the schematics I think the issue could be with U7800 but wanted some expert advice on where I might go next to validate. I do not have an Oscope to check clock signals. Thanks in advance.

PPVRTC_G3H = 3.09
PCH_SRTCRST_L = 3.07
PP3V3_S5 = 3.34
PM_DSW_PWRGD = 3.35
PP3V3_SUS = 3.34
PM_BATLOW_L = 3.32
PM_RSMRST_L = 61mv
PM_PWRBTN_L = 3.34
PM_SLP_S4_L = 0

 

[2informaticos]

First of all, welcome to the forum!

What is the exact PPBUS_G3H voltage?
Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L at same time.

PM_RSMRST_L can be pulled down by U7800, SMC, or PCH.
Check PCH_RTCRST_L and PCH_INTRUDER_L.

 

[DCSTechs]

Thanks for the welcome and the help.

PPBUS_G3H = 8.72

PM_PWRBTN_L dropped to .3 from 3.3 when PM_PWRBTN_L triggered

PCH_INTRUDER_L = 2.57 (seems low to me)
PCH_RTCRST_L = 3.07
PPVRTC_G3H = 3.08

 

[2informaticos]

PCH_INTRUDER_L is good enough.

"when PM_PWRBTN_L triggered"
Do you mean SMC_ONOFF_L?
If yes, PCH receives the power button information from SMC, but cannot reply while PM_RSMRST_L is pulled down.
Post diode mode to ground at PM_RSMRST_L with red probe at ground.

 

[DCSTechs]

sorry, yes I meant SMC_ONOFF_L

PM_RSMRST_L diode measurement is .415

 

[2informaticos]

You can try replacing SMC and U7800.
If PM_RSMRST_L still low, then bad PCH (CPU)...

You should already know the CPU on A1534 board doesn't have long life...

 

[DCSTechs]

Thanks and I have read a lot on here about these CPUs so hoping it is not.

 

[DCSTechs]

Thanks again for all of your help. One more question. Do you know where I can find the ICs? I have been unable to locate them.

 

[2informaticos]

Which ICs???

 

[DCSTechs]

U7800 and SMC for the 820-00244

 

[2informaticos]

SMC MUST be from donor board, same model.
I don't know if U7800 has specific firmware for particular board; maybe not, need to try...