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Hello, an 820-2879 came in with minor water damage around Q9807 area. green light OK ppbus_g3h 12.52v PP3V3_S5 OK Does not boot. What do I measure first? Thank you

CPU Vcore is coming high for a moment. U6100 was replaced with one from donor board. Same issue. About checking rails for shorts: do I also need to test all the sub-rails or just the main ones?

Hello,, I've got a MacBook Pro 15 820-2850 board that has a green light on the charger, both fans are pulsing every second. If I keep SMC_ONOFF shorted, the pulsing of the fan occurs at twice the speed. PPBUS_G3H is fluctuating between 12.54V and 7V. I also changed the C9560 cap, did not help...

Oh, and I do get a green light on the charger!

Hello, I have an 820-3115 with water damage around U6100 and U3890 areas. Cleaned up and now getting a single quarter fan spin, no loop. I started checking for shorts, but am not exactly sure what is meant by that: if I am to measure short to ground on PP3V42_G3H do I also have to measure all...

I don't want to sound mean, but this section is for MacBook logic board repair questions...

Does the machine chime at startup?

Okay!! It was a shorted high side FET, replaced Q7402 and short is gone. All S5 rails seem OK, I still get no fan spin. What next?

Sorry, guys. As stated in the beginning, I removed the inductor L7000 to inject some voltage and find the short. I didn't know I had to put the inductor back on in order to measure... So, with L7000 back in place I measure in diode mode and both pins show 0.009. In resistance to GND mode I...

Power is not applied. In diode mode I measure on L7000 and pin 1 is 0.496, pin 2 is 0,012. In resistance to GND mode I measure on L7000 and pin 1 is 7.64 MOhms and pin 2 is 20.8 Ohms. Does that make sense?

Resistance to GND on L7000 pin 1 is 35.31 kOms and pin 2 is 21.9 Ohms. The other two tests you ask me to do, I have not done before. Can you give an example of two points to check for low resistance to PPBUS, also an example of two points for shorted "high side" FETs? Thank you.

Somewhere in particular, or corrosion could be just about anywhere? Thanks anyway.

Let's have a look at another 820-2327 while we're at it. This one also has a green light on the charger but no fan spin. I got to the point where I found out that there is a short to ground on pin 2 of L7000. I used a bench power supply to inject some current on pin 2 and it does not get above...

I get 0.989V on pin2 of L7400 :( Oh, well. At least we tried. Thank you Duke.

You are right, I measured in diode mode. Resistance to GND on 3V42 is 22.84 kOhms. Taking a closer look I saw that there has been worked on this board before. U2801 was missing and I put it back in place. Now I get a fan spin for about 10 seconds, short pause for 2 seconds and then spins...

Hi, I am new to board repair myself but never heard of the term "no MagSafe". To start diagnosing you need an original Magsafe charger, and a known working DC-IN board. A possible scenario would be: "green light in the charger but no fan spin"

Am I supposed to measure resistance between these pins with the MagSafe disconnected? That's what I did and resistance between pins 17/18 is 21.2 Ohm, 27/28 is 20.5 Ohm. Resistance to GND on 3v42 rail is 0.324.

Hello guys, ancient board, I know, but still practicing. Board was clean except some mild corrosion on U7000. Replaced the chip and now I get 8.15V at pin 1 of L7000. When I plug in a good battery I get 12V on pin 1 of L7000. I short the SMC_ONOFF pads, no fan spin. What next?

Bright white screen!

Hi, got this macbook with no backlight. LVDS connector around ppvout_sw_lcdbklt pins was totally burned. Replaced the connector, got backlight back but no image. Mac is working fine with external monitor via displayport. Also tried another good display, no image still. What to measure?