Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

[kitt7]

Hi Everyone, I need help on my mac 820-00165-A. Here is the problem:

1. Mac does not turn on when power key pressed. Adaptor shows green then amber and stuck to amber. I tried to reset SMC using the keyboard techniques. Still it doesnt power up.

2. Prior to this, i plugged the MAC at 220v power outlet while it is off and took around 2-3 days plugged in at OFF condition without anybody using it for 3 days. The repairman i talked to said that it is wrong to leave the laptops OFF and plugged in and charged for very long time.

3. As i know a little about electronics, i opened the cover and unplugged the battery cable based on some advise in youtube, but still the problem persists.

4. Then I removed the board and checked on youtube on how to troubleshoot the problem and followed on it to check on some voltages. Here are my findings:

I checked the voltages on the 6 inductors:

L7130 - 8.5V is good. Fuse is good. so there is G3Hot
L7095 - 3.42v is good. That is why the charger has green/amber light
The other 4 inductors have 0 voltages.

Then I focused on the L7560 inductor which has no 3.3V. I traced circuit up to the TPS51980A powerchip and checked the voltages as follows:

Vin (input)(pin23) -8.5V - OK
VReg5 (output) (pin29) - 0V - NOT OK! which is supposed to be 5V
VReg3 (output) (pin22) - 3.28V - OK
VRef2 (output) (pin13) - 1.7V - OK
EN (input) (pin12) - did not check because my probes kinda fat and hard to reach the pin
EN2 (input) (pin21) - 3.3V - OK
VBST2 (input) (pin26) - Ov - Not OK!
SW2 (input) (pin 25) -0V - Not OK!
DRVH2 (output) (pin24) - OV - Not OK!

Pls note that i wasnt able to check other pins because I was afraid to create additional damage, etc.

Based on these readings, I deduced the problem is on the chip TPS51980A BUT im still having considerations on the the capacitor C7505 which is connected to VREG5 of this chip. Either the chip or the capacitor or both are the problems, or any other component. Pls. enlighten me on what to do. Thanks very much for all your help.

[kitt7]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

May I iknow if you have datasheet of TPS51980A. I cant seem to find in the net. thanks v much

[piernov]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

Board doesn't turn on with only DC-in board, fan and Magsafe connected to it?
Using an original Apple Magsafe 2?

Check SMC_PM_G2_EN on R8140 for example, and measure voltage and resistance across C7505.

[kitt7]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

sorry i meant my mac laptop doesnt turn on im using magsafe 2 power adaptor 45W designed in california. assembled china model A1436 (as per writings in the cover). i think it is original because we bought it at apple store.

SMC_PM_G2_EN shows 3.3Volts, Voltage across C7505 or PP5V_S5 shows 0.16volts. i checked the resistance across the c7505 (capacitor connected) it shows 2.9ohms. i also used continuity checker and it gives beep sound.

I was also able to check other pins like P5VS4RS3_EN and it gives 0 volts.

Is the capactor C7505 defective? or is the TPS51980A? or any other component?

thanks very much

[piernov]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

Ok so that confirms PP5V_S5 is shorted to ground.

Easiest way to find a shorted component is by injecting some voltage with a lab power supply and finding the component that heats up.
Although there are not a lot of components on PP5V_S5 so you could remove them one by one until the short is gone (the resistance should go up in the kiloohms range). Start by removing the capacitors C7505/C7400/C4810, then the IC U7501/U7400. (take a look at the boardview)
If any of those components look funny it may be the culprit.

[Gimi]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

disconnect keyboard battery and check if you get a fan spin

[kitt7]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

Thanks Piernov and Gimi. I removed C7505 (capacitor nearest the VREG5 pin 29 of U7501). Problem still shorted to ground. Then I removed C7400(capacitor of U7400), NO MORE SHORT to GROUND! I tested via multimeter the C7400 disconnected and it really shows the capacitor shorted. Thanks very much Piernov for your help!

Now I have to find the capacitor c7400 (10uF 10V 20% x5R 603) to replace it. Is it ok for now to check voltages or turn on the laptop (without the C7400) while im still looking for a replacement capacitor? so that I can rule out any other component problem or IC problem?

My idea is that since the C7400 was shorted. The U7400 couldnt have been damaged because there was no voltage supply Vin in the first place. I have to check the U7501 IC which might be affected since its 5V output VREG5 pin 29 was the one shorted to Gnd due to the bad capacitor C7400.

Any ideas?

Thanks.

[piernov]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

U7400 may not work properly without C7400 (as there may be too much ripple on the PP5V_S5 power rail when it enters U7400). It doesn't travel a long way from U7501 and C7505 though so it may be fine without it.
This kind of capacitor can probably be found on scrap board if you have any. Find a capacitor with the same package size and use capacitance mode of your multimeter to confirm it is 10uF. It is on a 5V rail so the voltage rating shouldn't be an issue (will work with 6.3V and up).

Your assumption about U7400 and U7501 is right. But there might have been a voltage spike on PP5V_S5 that killed C7400 and could have damaged U7400, even though it's highly unlikely.

[kitt7]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

Thanks again Piernov. So I checked the voltages again this time. Pls note that C7400 is not attached thus i dont have any bypass cap before the Vin of U7400. The ff are the voltage reading i got:

For U7501:

Vin (pin23) = 8.55 volts - OK
VREG5 (pin29) = 2.5 - 4.95V (erratic - going back and forth, etc)
VREG3 (pin22) = 3.28V
VREF2 (pin13) = 0.3 - 1.8V (erratic - going back and forth, etc)
EN (pin12) = 0.6 - 2.8V (erratic - going back and forth, etc)
EN2 (pin21) = 0.8 - 3.3V (erratic - going back and forth, etc)
VBST2 (pin26) = 3.5 - 4.7V (erratic- going back and forth, etc)
SW2 (pin25) = 0.8 - 8V (erratic - going back and forth, etc)
DRVH (pin24) = 3.5 - 19V! (erratic - going back and forth, etc)
EN1 (pin4) = OV!
PGOOD1 (pin5) = 0V
PGOOD2 (pin20) = 0.23 - 2.9V (erratic - going back and forth, etc)

I also checked my PP3V42_G3H and i got 3.42V - ok.

Now my voltages have gone erratic Is it due to the capacitor C7400 not being present in the circuit or due to the defective U7501 (TPS51980A) or could be damaged U7400 (which is highly unlikely)?

Pls. enlighten. Thank you very much.

[piernov]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

With those measurements, C7400 or U7400 should not be the issue. However as it becomes a bit more complicated at this point you'd better replace that capacitor first.
Apparently the short to ground is gone on VREG5 (since it's able to go to 5V), but since it is pulsing (and the enable signals as well), U7501 may need to be replaced.

[kitt7]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

Thanks. you are right. il fix capacitor first and get voltage readings then if i dont get standard reads, il have the U7501 replaced. will keep you posted. wil get the cap 2days from now. hope nothing was affected after my getting voltages witbout c7400 installed

[chimei]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

hi, I got a similar but not exactly problem about this model motherboard.

the problem is the computer when I connect the power supply it will automatically turn on without need to press the power button

For U7501:

Vin (input)(pin23) -8.5V
VReg5 (output) (pin29) - 5.16V
VReg3 (output) (pin22) - 3.28V - OK
VRef2 (output) (pin13) - 2V - OK
EN (input) (pin12) -3.4v
EN2 (input) (pin21) - 3.43V - OK
VBST2 (input) (pin26) - 8.5v -
SW2 (input) (pin 25) -3.35V -
DRVH2 (output) (pin24) - 3.3V
EN1 (pin4) 3.341v
PGOOD1 (pin5) - 3.3v
PGOOD2 (pin20) - 3.4v

what could be the possible reason ?
thx

[piernov]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

After disconnecting battery that's normal behavior. What's the issue? I don't see how it is similar to the previous problem, so if you really have an issue with the Macbook, open a new thread.

[chimei]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

thx, piernov.

my macbook motherboard model is 820-00165-A.

the problem is before I disassembly it, when I plug in the charger, and the battery is connected, the macbook can not turn on by pressing the power button. If I press the power button, Adaptor shows green then amber.

if I disconnect the battery, plug in the charger, the laptop will automatically turn on and can get into the system. but after I shut down the laptop, can not turn on the laptop by using the power button. only can turn on by unplug the adapter and plug in again.

I check the voltage
For U7501:

Vin (input)(pin23) -8.5V
VReg5 (output) (pin29) - 5.16V
VReg3 (output) (pin22) - 3.28V - OK
VRef2 (output) (pin13) - 2V - OK
EN (input) (pin12) -3.4v
EN2 (input) (pin21) - 3.43V - OK
VBST2 (input) (pin26) - 8.5v -
SW2 (input) (pin 25) -3.35V -
DRVH2 (output) (pin24) - 3.3V
EN1 (pin4) 3.341v
PGOOD1 (pin5) - 3.3v
PGOOD2 (pin20) - 3.4v

everything seems ok, what cause that issue?

thx.

[piernov]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

Bad keyboard most likely.

[chimei]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

But why if I press the power button, Adaptor shows green then amber.
I check the keyboard rail, if I press the power button, the voltage will become 0V, it means the power button is working.

[piernov]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

It's doing SMC reset.

[xalapamac]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

Hi, I need your help with a similar problem. The base plate is 820 - 00165 and was damaged by liquid on the Smc (u5000). Clean the area with isopropyl alcohol and remove the components with sulphate (C142y R195), replace them with one of the same value. The Charger does not give green light, and I have these readings:
PPBUS_G3H=8.1v,
pp3v42 _ g3h = 3.41v,
PP5V_S5=0v,
pp3v3 _ S5 = 0v,
PPVRTC_g3h=3.41v.
SMC_BC_ACOK=3.38v.
Sys _ onewire = 3.39v.
SMC_ pm _ G2 _ en=0v. The reading in diode mode of this signal is 528.

that you recommend me?

[piernov]

Re: Need help on Macbook air 1466 with board 820-00165-A. Doesnt turn on

Please open a new thread for a different problem. You clearly have an issue with SMC here…