820-2915 no video

[hosoi]

Hello, this MP turns on, charge, have green and orange light at MagSafe, but there is no video and no chime either, there is no sign of water or burned parts, flashed the spi just in case and nothing, removed the ram and no beep, connected external monitor and nothing. Also, did a GPU bypassany clue where to start?

I have these readings:
PLT_RESET_L __3.34
PP5V_S5__5
PP5V_S3__5
PP5V_S0__5
PP3V3_S4__3.34
PP3V3_SUS__3.34
PP3V3_S5__3.34
PP3V3_S3___3.34
PP3V3_S0__1.34
PP1V8_S0__1.77
PPVCORE_S0_CPU__0.75
PP3V3_S0GPU___3.34
PPVCORE_GPU___1.11

BR

[piernov]

Re: 820-2915 no video

Exact voltage on PPVCORE_S0_CPU with and without RAM?

[hosoi]

Re: 820-2915 no video

PPVCORE_S0_CPU
with ram 1.14 then drops to 0.75 few seconds later
without ram 1.15

[piernov]

Re: 820-2915 no video

100% sure there's no beep without RAM?
No activity on USB drive with RAM?
It could be something related to audio circuit like U6880 or U6201.


What method did you use to disable dGPU?

[hosoi]

Re: 820-2915 no video

yes, no beep without ram at all, no usb activity.
to bypass the gpu someone gave a bios with the gpu disabled and I removed 2 resistors R8904/11.
I checked that area and looks good to me. what exactly should I look for in order to determine that everything is good, since I'm a newbie.

[dellxps15]

Re: 820-2915 no video

volts on r7402 both side,

bios voltage ? all pin

[hosoi]

Re: 820-2915 no video

r7402 -2____12.53
r7402 -1____12.43 fan stopped when I measured here

bios
1___3.34
2___3.32
3___3.33
4___gnd
5___0
6___0
7___3.15
8___3.34

[dellxps15]

Re: 820-2915 no video

7402 is 90.9 k ?

[hosoi]

Re: 820-2915 no video

r7402 88.5K

[hosoi]

Re: 820-2915 no video

any help or sugestions?

[dellxps15]

Re: 820-2915 no video

did u put a cable from c9711 to r9701both soldered from ic side ?

edit: loks like your problem is that gpu bypass....

for chime to come back... hold Command Option P R and power on the macbook.... hold them till it will reboot 2 time and second time with chime.

for black screen no backlight if u didnt have that jumper from ccapacitor to resistor, put back r8911 resistor and ull get backlight working again.


edit: 1st try is to solder wire from c9711 to r9701 like shown in the attached picture... if no backlight then put r8911 r8904 back and see if backlight comes in.

[hosoi]

Re: 820-2915 no video

thanks for replying. I did GPU bypass just to see if the problem was the GPU, but since didn't work I flashed the original bios, and soldered the resistors back, so everything is back to normal but still doesn't work. at this point dont know what to do.

BR

[dellxps15]

Re: 820-2915 no video

external monitor works only when os is almost loaded.
did u reset pram ?

[piernov]

Re: 820-2915 no video

External display requires working dGPU anyway. And dGPU is probably dead.
Even with a dead dGPU it should beep without RAM, but it may not POST properly with RAM.

[hosoi]

Re: 820-2915 no video

external monitor works only when os is almost loaded.
did u reset pram ?

pram reset doesn't work, external monitor doesn't work either

[hosoi]

Re: 820-2915 no video

External display requires working dGPU anyway. And dGPU is probably dead.
Even with a dead dGPU it should beep without RAM, but it may not POST properly with RAM.

how can I check if this MB POST or not? sorry for my ignorance.

[hosoi]

Re: 820-2915 no video

why do you think is not beeping, but the LED status indicator flashes without ram?

[piernov]

Re: 820-2915 no video

The speakers are plugged in, right?

[hosoi]

Re: 820-2915 no video

sure, i'm also using external speaker

[hosoi]

Re: 820-2915 no video

I connected the external speaker to test the normal booting, I know that the external speakers wont sound when the RAM are not present, just clarifing.