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820-02016 5V .450A liquid spill on CD32. Pulsating PMU U7700

S

SolderFungus

Member
I have A2337 with liquid spillage on the CD32s and UF400/500 chips.


One of the CD32s had a short on I2C_UPC0_ATCRTMR0_SCL however that is now restored.
I now get 5V on USB-C and the device is cycling up to .450mah.
The thermal cam indicates rapid heat pulsations on U7700, however there is no visible liquid spilling around that part of the board. All of it is located on the tail end by the CD32s and UF400/500.

Can the CD32s cause the PMU to fail? It is not the easiest part to replace so I hope there is something else I can check before replacing it. Asking for advice. Thanks!

PPVDD_CPU_SRAM_AWAKE R 623 D .247
PP3V8_AON_VDDMAIN R 1.9K D .350


PPVDD_PCPU_AWAKE R 31.8 D 0.037
PPVDD_ECPU_AWAKE R160 D.165
PPVDD_CPU_SRAM_AWAKE R 590 D.242
PPVDD_SOC_S1 R 34.8 D 0.043
PPVDD_GPU_AWAKE R 32.4 D 0.041
PPVDD_DISP_S1 R 252 D .201
PPVDD_DCS_S1 R 707 D .264
PP1v4_LDO_PREREG R 1.32K D .275
 
2informaticos

2informaticos

Administrator
Staff member
"One of the CD32s had a short on I2C_UPC0_ATCRTMR0_SCL however that is now restored"
Which was the culprit?

Check diode mode to ground on CD3217 LDOs; compare with good board.

What about PPBUS_G3H and 3V8_AON voltage behavior?
 
S

SolderFungus

Member
"Which was the culprit?"
I believe it was a short under one of the CD32s.
I found the short with diode mode and it got restored to OBDATA values after a reflow with flux.

Found one deviation on one of CD32 LDOs

PP3V3_S2SW_USBC1 LDO CAP on one of the CD32s read .352 VS .462 from OBDATA
Is OBDATA acceptable? I can acquire a working mobo if not.


I cannot find PPBUS_G3H in schematics or Broadview for this model but if that refers to PPBUS_AON (?)then it's jumping around from 9-12.2V

3V8_AON = 3.8V and appears to be stable
 
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