HP DM1 netbook without 5v voltage

[JulioChuts]

Hello, folks from badcaps. I'm coming here to ask for help because I'm facing a tough issue on my workbench.

I received this HP DM1 netbook at my station, and it's not turning on, even though the charger light is on.

After analyzing the circuit, I noticed that there was no 5V voltage. I started measuring the PWM, and eventually, I decided to replace it. I changed the PWM about 3 times, but still no luck. I also checked for shorts and even replaced the MOSFETs, but nothing worked.

Could anyone lend me a hand? I'm feeling quite lost, to be honest.

I'll leave some pictures and the circuit diagram here for anyone who wants to take a shot at it.

The IC responsible for generating these 5V is PU8. I have 5V at LDO5, but when I check PL508, it's showing zero, and the LL1 output is also zero.

MOD Edit: Schematic moved to new thread -> https://www.badcaps.net/forum/showthread.php?t=121299
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[mon2]

Re: HP DM1 netbook without 5v voltage

Remove all power. Meter in resistance mode.

What is the exact resistance to ground at PL508?

[JulioChuts]

Re: HP DM1 netbook without 5v voltage

It's reading about 35.31 ohms, it's not exactly a short circuit.

What I find strange is that when I apply voltage, the current goes up to 100 amps on the asymmetric power supply, and it starts to heat up. I've already replaced it about 3 times, as I mentioned before.

[janocko]

Re: HP DM1 netbook without 5v voltage

You can check voltage PU8 at pin1 or entrip1, its to enable 5v alw. then compare with entrip2 (this is to enable 3v alw)

[JulioChuts]

Re: (Good news) HP DM1 netbook without 5v voltage

Hello everyone, just wanted to share the results with you.

I want to thank "janocko" for the tip to check entrip1; indeed, it was without the enable voltage. After studying the schematic a bit, I realized that to generate this voltage, it required a signal from the PCH. Initially, I thought I might have to do reballing, but upon examining the PU8 datasheet, I found out that if I cut the trace connecting to the PCH, it was possible to activate the 5V voltage. So, that's what I did, and it started generating the 5V voltage. However, it still wouldn't power on, and I began to suspect that some voltage from the PCH was indeed necessary.

Then, I noticed something amusing: the power button was lacking the 3V required to turn on the system. Testing the continuity, I saw that the trace was broken. With a gentle scraping of the trace and connecting my alligator clip to the ground, I touched that trace, and the notebook turned on. After that, I connected the screen to see if it generated an image, and it worked!

It took a little effort, but it worked. Thank you so much EVERYONE for your help! :grupo: