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checked again, for sure there is usb activity.. also, if it means anything, caps lock green light comes on and off when pressed.. will try dfu restore again.. anything that can cause the gpu not to kick in or just the gpu itself?

by locked i mean find my mac was on?

i might be getting it wrong, because i think there is no vcore now.. which i'm pretty sure there was before (there was a chime, pram reset) etc... any idea why a restore would cause that? maybe it was locked?

these boards should have cpu vcore , on the table - when only connected to charger without anything else connected?

hi got a usb flash drive with a led showing activity looks like there is activity on this mac when it's on..

sorry about that, but can't find the "how to" section can you please send a link? just to make sure wheter it has or not usb activity...

when i connect usb mouse i get the light working on it. nothing on external video pram reset does not work after the restore can't get the mac into Target disk mode... interesting because before the restore it had pram reset and chime. now those gone..

correct, DFU restore finishing with no error but again, black screen (backlight is on, but no apple logo or os installation) also, no chime or pram reset after the restore. i tried to restore a few times, from machine with catalina and also big sur.. both same result...

hi pram reset chimes but does not solve the problem tried revive option - didn't do the trick same for the restore option. now the mac no longer chimes but comes on with a bright black screen, than dims and nothing more. also pram doesnt respond now..

Hello having a problem with 820-01700-05 from 2019 16" macbook pro unknown history the machine is powering on (chimes) probably to login screen (double clicking the power button activates the voice over option).. the backlight seems to be on but no image on display and also not on external...

PPBUS_G3H is 0.3 ohm to ground. big coils around cpu and gpu, i hope i understood correctly - measured for exa. on L7211 - 2.7ohm L7221 - 2.7ohm L7231 - 3.0ohm LA340 - 1.6ohm LA640 - 1.4ohm LA650 - 1.4ohm measured all with black probe to ground between ppbus_g3h and L7211 there is 2.6ohm my...

Hello working on a board 820-01814-a from a1990 machine. the mac is dead, does not charge or power on.. while checking with usb c measuring tool on the charger it is drawing 5.17V and 0.01A took out the logicboard, looks very clean, missing PPbus_G3H and also missing every other power rail...

thank you louis and duke.. can you please give your thoughts on the 820-4924 with keyboard not working.. i just posted all the reading from the TPAD connector.. https://www.rossmanngroup.com/boards/forum/board-repair-troubleshooting/38274-820-4924-no-keyboard/page2 many thanks...

hi the lcd is good with another board the lines and garbage on hdmi screen, with the lcd disconnected meaning the board is toast?

hi here all measurement on diode mode all pins of trackpad connector (red probe to ground) o.l is ok on pins 1-13? 1 - o.l 2 - 0.000 3 - o.l 4 - 0.000 5 - o.l 6 - 0.000 7 - o.l 8 - 0.000 9 - o.l 10 - 0.000 11 - o.l 12 - 0.000 13 - o.l 14 - 0.000 15\17 - 0.000 16 - 0.000 19 - 0.746 20 - 0.676 21...

seems like it's been messed with.. i've passed on this one, giving it back to the owner... this thread can be closed... btw john, duke - can you please give your opinion on the 820-4924 no keyboard \ trackpad...

ok thanks, just never ran into a beep in a macbook... so i've done this diagnosing.. the cpu and ram area looks very clean, no visible corrosion.. i replaced the next parts that was corroded around the board.. c8300 d2920 c8030 c2350 c8051 all of those was corroded or burned and were...

hi it's 11.5 k ohm on USB_TPAD_P and 60k ohm on USB_TPAD_N measure the same on a good board and it's the same.. the other side on this connection is the cpu so no way to measure when trackpad connected.. the PPVIN_S4_TPAD_FUSE is 12.56v is that normal? on the schematic says 8.6v..

:| i don't see a way to check when the trackpad is connected... can you say on which pin of the trackpad to measure? maybe on the boardview there is another point to check from? i also have a 820-00138 board with almost the exact same issue didn't thought would be such a nightmare to diagnose...

i agree that it seems like trackpad is maybe causing short to ground not by trackpad but on the logicboard... where can i measure pch or usb while trackpad is connected \ disconnected?