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I just got A1707 with the same type of short circuit on the PPBUS_G3H line, and 1V injection detected a shorted cap on the audio line.
I agree with what you said, but can we clarify what internal ohm shortage or case scenarios we should look for before any injection? Even on low voltages...
So far I have reflowed the GPU just in case if it is a cold joint. Same behaviour, loads Windows every time but shuts when test engages the GPU. Stable when test is run on the Intel GPU.
UCd the board as GPU Core MOSFETs were soaked in a thermal paste.
I went ahead and reflowed and...
Reflowed, it seems to be the same. 20V 0.20A Initially, after a couple of seconds drops and stays at 20V 0.02A board only. 20V 0.5A with battery.
Tried a different case 20V 1.2A seems to be charging. But not turning on
SMC reset didn't work
Working on this Razor Blade RZ09-01953, which seems to work fine on light tasks or when the GPU stress test is running under Intel, but the minute it runs under Nvidia, it cuts power.
Could it be GPU failure? I ran some GUI mem tests and came up fine. MATS GPU RAM test doesn't seem to boot
Replaced the charging chip with the B version. It worked fine and passed all tests. Left on the shelf, and the customer came to pick it up. Not turning on 😲
Back to the repair bench. I am getting 20V 0.02A. No short circuit on coils, and no heat signature.
PPBUS_G3H - 13.05V
PP5V_S5 - 5.1V...
+SDC_IN - 18.8V while off 18.4V while on without battery
PQ1900-04 Fluctuates 14.7 - 15.1 without battery and not turning on while I am measuring it
If I measure after it turns on 18.6V
Couple 2R2 looks bit corroded, but they all measure fine including their traces
Seems something is...
1-2 - 2.37Ohm
14-15 - 4.65Ohm
It cycles on each of these every sec, so I added both measures before and during the cycle
Charger Only - B+ 13.56V/0A - 13.6V/1.4A
Battery Only - B+ 9.5V - 8.3V
Charger & Battery - B+ 13.34V/1.5A - 11.5/4.8A