820-00165 pulsing

[Francisco.s]

Hi, have a 820-00165 pulsing once. All voltage seems to be ok only for a moment, then it stops and takes 22 miliamps from power supply and fan stops.

cpu vcore rises to 1.8v and PLT_RESET_L goes hi level also.

SPI ROM have good pulses, but its contents are not modified, even a clean ME region remains intact. (CPU doesn't attempt to write new ME data)


SMC bypass shows the same symptoms, but fan spins faster. Charger circuit works ok and battery can be charged properly.


I have cleaned ME region and reset pram via Medusa programmer and even write a completely new bios with the same programmer.

How can I test if memory is working properly? I cant find any signal equivalent to ddr reset in the circuit diagram.

[mon2]

https://www.logi.wiki/index.php/820-00165_Pulsing

[Francisco.s]

Originally Posted by mon2

https://www.logi.wiki/index.php/820-00165_Pulsing

Hi moon2, I've read all related threads about pulsing in 820-00165 motherboard and perform some of the tests they mention.

Probably i've not tested the failed component, but I'm starting to think that a damaged cpu could be the problem.

Forgot to mention that some corrosion (sulfated capacitor) affected the +3v rtc circuit.

[Francisco.s]

After replacement of U7400 the board is working now.

PP1V2_S3 is the output of U4700, and it was ok before replacing this chip, but the waveform at pin 1 of L7430 was distorted and causes DDRREG_PGOOD not to be stable.

One of of the first thing I did, was remove Q8150 in order to disable ALL_SYS_PWRGD protection, but didn't see that this signal goes to low level via R8168 when a problem is detected in U4700 circuit.

So problem is solved.