820-2796 board no PM_SLP_S4_L

[Chip Chip]

Hi Duke,

on this board i had no power ( no green light). A little bit of water was on the LIO board. On the LIO board i found a corroded contact point. After fixing that now i have a green light. The logic board itself looks absolutely fine. But machine is not powering on. My meassurements show that there is no S3 state. S5 voltages are there. At the end i found out that there is no PM_SLP_S4_L. Now what to check?
I looked at the schematics and wanted to meassure PP3V3_G3_RTC voltage but the schematic is confusing me. When i look at the schematic and compare this with the board view software than this voltage is called PP3V42_G3 in boardview software. Anyways this voltage is missing on R1920 and R1921.
What is the next step to meassure? Any ideas?
Thank´s!

 

[dukefawks]

RTC voltage is coming directly from PP3V42 bus. If you have a green light then 3V42 must be ok and there should be 3.3V at R1920. If it really is not there then there must be a corroded trace. Also these boards do not auto power on, you need to short the power pads on the board.

 

[Chip Chip]

Oh man! I just checked it today. And yes, the RTC voltage is there...... I tried to power on the machine with power on pads but nothing
PM_SLP_S4_L still missing.

 

[dukefawks]

Voltages on Y2810?

 

[Chip Chip]

Pin1 = 3.3V / Pin 4= 0V

 

[dukefawks]

Yeah, that is wrong. There is probably corrosion under the MCP right on the side where the Xtal is. Put some flux under it and heat it but do NOT reflow. Just let the flux cook for a bit to clear the crap under the chip. Voltages on the Xtal should never be more than 1.6V on each pin.

 

[Chip Chip]

just did this but no result . The same voltages

 

[dukefawks]

The alternative is to replace the MCP, but these boards are not worth that. What is resistance to GND on bot Xtal pins?

 

[Chip Chip]

Hmmm....

On PIN 1 = 240 OHMs / PIN 4 = 11 OHMs

Just a question....Do you speak german?

 

[dukefawks]

Auf Deutsch ist möglich aber lieber auf Englisch, dann kann jeder hier es verstehen.

Yeah those values are way too low and that indicates a dead MCP. These boards are too cheap to go and replace it, this board is toast.

 

[Chip Chip]

Thank you Duke ! DANKE !