A1708 820-00875-01 no image

[hgoncalves]

Hi,

I have an A1708 820-00875-01, that seams to have no image, even on external monitor. On USB metter I get 19.4V and 0.59A without battery.
It seams to power on (I hear the "little Chime") but get no image. I have tried with two different LCD, but without success. Tried an external monitor, but same behavier.

Can you help?

 

[2informaticos]

Any history available?

What is the final CPU core voltage?
Did you check for USB activity?
Caps Lock light reacts?

 

[hgoncalves]

Hi,
The client says that it stoped working.
I have USB activity, and CPUVR_SW1 = 4V and PPVCCCPU_S0G_PH1 = 0.9V
CAPS work fine

 

[2informaticos]

Usually VCORE drops to 0.6v when board is working; 0.9V is more like stuck board.
But if Caps Lock reacts, then board is working.

0.59A doesn't look good for me, should drop a bit after 10-15s.
Are you really sure about Caps Lock and USB activity?

 

[hgoncalves]

Yes. I'm sure about caps and USB activity (I use Chipmunk USB Tester).
You're right about the consume. The amperage drops to arround 0.35A after a few seconds, and vcore also drops a bit to around 0.6V (I thought that the inicial amperage / voltage were the most important, and didn't realize that you asked the final voltage of vcore. Sorry!).

 

[2informaticos]

I can only think on iGPU, as you lost both internal/external video.
Not common, as this board has series caps on data lines between CPU and LCD connector.
But still direct connection on some signals.

 

[hgoncalves]

Hi,
Is there any way that i can test or confirm it?
I Now I have here another one that has the same problem, and I'm doubting if my USB C > HDMI adapter is bad...

 

[2informaticos]

Test your USB-C to HDMI adapter on working machine.

 

[hgoncalves]

The adapter is OK. Just tested with another mac (different model), and it works.
Is there anything that I can do on iGPU cases, or in this particularly case?

P.S. Just spoke with the client and she confirms that one night it was working fine, and the next morning it didn't show any image.
It has no signs of liquid nor corrosion

 

[2informaticos]

A1708 is Apple garbage.
If you have USB activity and no internal/external video, only bad iGPU.

Try known good BIOS, just in case...