For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
Pulse on pin 7 ok, no pulse at pin 3.
I had pulses on SMC_DELAYED_PWRGD, but not at each trigger of SMC_ONOFF_L
Removed U1950, I got a couple of pulses on SMC_DELAYED_PWRGD, then no more. Do this pulse should appear at each SMC_ONOFF_L trigger?
R5191 ok
Fan spins first low speed a few seconds then high speed when I put the scope probe on pin 7, with power supply giving 200mA
What can I do about SMC_DELAYED_PWRGD not always there?
I tied them without U1950, and for some reasons I had pulses on SMC_DELAYED_PWRGD
Reinstalled U1950, I could start the board (blinking folder) by triggering SMC_ONOFF_L, with power supply giving 700mA, a bit higher than normal. The board did not start alone when giving power.
When trying later again: impossible to start.
Then I tied together pins 5 & 6 with U1950 present, I have pulses on pins 7 and 3, but the board does not start, SMC bypass or not, just fan spinning 1 second, as before.
Finally found a tiny corrosion spot around C4090 C4691 linked with PP5V_S4RS3, which gave also a pulse previously. Cleaned around and now the board starts alone, let's see for how long.
Thanks for this very detailed investigation! Always learning
Cold, the board does not want to start. Again, no pulses on SMC_DELAYED_PWRGD
I tied again together pins 5 & 6 with U1950 present, I have pulses on pins 7 and 3, but the board does not start, SMC bypass or not, just fan spinning 1 second, as before. Don't know where to go. It worked, I could boot in a SSD, but now dead again
Indeed. I heat the board square cm per square cm, I finally found that heating U7200 allowed to start the board. Tiny short between pin 10 and 11...
Now ok, thanks!