A1708 820-00840-A no power

[hgoncalves]

I have an A1708 820-00840-A with no power.

It has 19.8V on ampmeter, but 0.01A

PPBUS_G3H = 0.066V and 0.412 on diode reading

It seams that someone has already replaced U3100, and worked on the U6990 area. Client said it was in another store before, but dosen't know what was done there.

Can you help?

 

[2informaticos]

Remove F7000 and check C7050 voltage.

 

[hgoncalves]

Hi.

It seams that F7000 was already removed on the other shop and I din't noticed it.

C7050 has 19.8V

When I've resoldered F7000 again, the ampmeter reboots at 4.5V

 

[2informaticos]

"C7050 has 19.8V"
!?!
Looks good for you?

Check Q7030/40 for internal short.

 

[hgoncalves]

I couldn't check TBA_GATE_Q3 of Q7040 because I can't find any test point to do it. Shal I lift it up?

Everithing else seams to be ok on Q7030/40

 

[2informaticos]

How can you get 20V at F7000, if none of them shorted?
You must check between their pins, not in respect with ground.

 

[hgoncalves]

Sorry, I havent understood it first.

It seams that TBA_LX2 it's shorted with TBA_PHASE2, and TBA_LX1 is shorted with TBA_PHASE1.

I'm not sure if their just low resistence. On schematics seams that they are connected, but not sure if my reading is right.

Everything else seams to be OK

 

[2informaticos]

Do you really get 20V at F7000?

 

[hgoncalves]

Hi.

With F7000 soldered I get only 5V and than mac reboots.

However, with F7000 lifted, I get 20.27V on F7000 pad 1 (PPVBAT_G3H_CHGR_REG), and ampmeter stays steady at 19.8V. and 0.01A

On PPVIN_G3H_P3V3G3H I also have 20.22V and using an original Apple charger

 

[2informaticos]

Don't you plan to check Q7030/40 as I explained?
If you don't know how to check a MOSFET, replace them directly.

 

[hgoncalves]

Hi.

I've checked both (continuity beetwen their pins), and I thought that they were OK. However, after replacing them the mac powerd on again. You're right as usual.

How should I test MOSFET's like those ones?

 

[2informaticos]

Doesn't matter if you have single, or dual MOSFET.
Just identify the S-G-D pins and check as Google shows you.