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I had assumed that the trackpad click was a sign of life on all of them.
Plus the fact the power button would seem to turn the trackpad on and off.
However, no signs of life from any USBC port with a USB with a LED on it.
PPVCC_S0_CPU = 0v
PPBUS_HS_CPU = 12.56v
PPVPCORE_S5 = 0v...
I get 20 volts to F3001 when connected to the outer USBC port on J3300.
The trackpad clicks, so the unit is turning on, but there is no display.
The power button will turn the unit on and off - i.e. the clicking will stop, or start, again.
There is no signs of any liquid ingress to...
I have a dead 820-00269 from an A1706.
I get 20v on F3001, however no voltage on F8400.
I removed F8400, and injected 1 volts into pin 1 and found U7960 getting very hot.
I removed that and there still appears to a direct short (zero ohms) to ground on the pads of...
Thanks again for your advice 2informaticos.
Unfortunately, that job went pear shaped. :(
What temperature do you need to remove UB400?
I ended up overheating the board, to the point that other components started floating....its game over unfortunately for this board.
I read that all 4 CD3215...
Hi again 2informaticos.
Thanks for your advice once again, and sorry for the delay.
I measured all 4 LDO rails on all four CD3215 chips.
In diode mode with red to ground, most rails measure between 524 & 570.
However, 2 rails do not, and appear as short circuit.
I have a 820-00239 that appears dead - no life, no fans.
No USB activity at all.
No signs of any liquid anywhere on either size of the board.
Tried with known good AC adaptor with just the bare board.
I don't seem to get 20v anywhere - the most I get is 5.7 volts.
Hi again all.
Short circuit to ground on PPVRTC_G3H.
I suspect the CPU is dead, but thought I'd check before writing it off.
Magsafe light OK, no fan, no chime or anything else.
No signs of liquid ingress or other damage.
I've removed all caps on PPVRTC_G3H, short to ground (0.08Ω)...
I have an 820-00928-A that does not detect the internal SSD.
This unit was apparently water damaged.
Another technician cleaned the board, unfortunately, so I cannot see where the liquid got onto the board.
There are no signs of corrosion anywhere.
Booting from a Monterey boot disk...
Cleaned J6100 - was a tiny residue of crap still there surprisingly, but no change.
Cleaned both U6100 and U6101 - no change.
Checked voltages on SPI Bus Series Termination resistors.
SPI_SMC_MISO 3.31v (measured at pin 2 of R6114)
SPI_SMC_MOSI 0v (measured at pin 2 of R6115)
Sorry, i had tested video prior to checking if there was USB activity. I guess its easier to go the other way.
Still learning. :)
I was also rushed yesterday, so apologies for the typos... PPBUS_G3H is 8.56v.
PLT_RESET_L = 3.31v
I have a water damaged 820-00165-A that has no display, either on the internal panel, or on an external screen.
There is zero change on the screen when power is connected.
I cannot see an Apple logo or folder question mark while shining a light from the back.
I have tried another...
An interesting one.
We have an A2338, running Monteray, that has no back light from the moment you turn it on, until you have logged in with your password, when it will turn on, and stay on.
i.e. the Apple logo doesn't have a back light at all, or the login screen.
We have tried two...
Thanks again 2informaticos.
I only have a CH341A programmer, with a standard 8 pin SOIC adapter.
To load a good BIOS, do you have to manually solder wires to the board, or is their an adapter I can just plug in?
Never programmed a Mac BIOS before.
And, given I can get the unit to boot in Target...
I rechecked CPU core - goes to 0.69v then stays there.
I get USB light flashing on all 4 USBC ports.
Yes, Capslock light works correctly.
Touchpad does tap correctly when unit is turned on.
NO Chime after PRAM reset - no chime, ever.
No fans, ever.
The macbook appears as a disk...
That makes sense.
Thanks again for your help.
With the screen disconnected, red lead to ground, all seem to read around 256:
Diode mode to ground readings: