820-00165 - PP5V_S4RS3 8v

[Palhano]

When connecting to the power supply, it quickly draws 0.600A and turns off, the cooler even starts to spin. The logic board had some oxidation on R8164, R3921 and R3558, I fixed everything and the problem persists.

With the thermal camera I noticed that the U7600 and U7400 were heating up when the board turned on for a few seconds. I replaced both of them, the board started to turn on, drawing 0.400A, but both components continued to burn. Then I discovered that the PP5V_S4RS3 was at 8V.

I tried again by replacing the U7501, U7600 and U7400, but it didn't work!

Any tips?

 

[2informaticos]

First, check for short between pins 1-8 of Q7520.
Next, check correct values (ohm scale) of R7520/1/3 and their traces.

 

[Palhano]

The Q7520 does not have a short circuit, I forgot to mention it, but I had already replaced it, but it did not solve the problem.

Everything is fine with the resistors!

Comparing it with another good board, I found something different with the R7520. On a good board, the value increases, on a faulty board, it increases to 9k, I removed it from the board and measured it, it reaches 47k, when in doubt, I replaced it, but it still has 9k on the board.

 

[2informaticos]

Correct value can only be checked out of board!
Only low value resistors (usually under 100 ohm) can be checked onboard; depending on the circuit position.

 

[Palhano]

Thanks for the tip!

So, outside the board, they are OK. Any suggestions as to what could be causing these 8v?

 

[2informaticos]

Broken trace for R7520/3, for example...