820-2936-B Green light, chime, fan Spin - NO VIDEO

[xalapamac]

The motherboard in not liquid damage

I have all the voltages you need, but I found that with the RAM PPVCORE_S0_CPU. = 0.8v

Removing the RAM is measured PPVCORE_S0_CPU = 1.15v and beep for 1 second and repeats the beep every 5 sec.

ALL_SYS_PWRGD = 3.3 v
SYS_PWROK_R = 3.3 v

Any idea where to repair it?

[zpi]

Re: 820-2936-B Green light, chime, fan Spin - NO VIDEO

Hello,
If you have Chime, you have working cpu and rams, so forget about these measurements. You should check if LCD is recognized.

First please measure:
L9008 Pin 2
L9004 Pin 2

Lcd has to be connected when you do measurements.

[xalapamac]

Re: 820-2936-B Green light, chime, fan Spin - NO VIDEO

The LCD is testing it on another motherboard and it works perfectly. Turn on and gives perfect background light.

With the screen and the RAM connected gives me these signals

L9008 Pin 2 = 3.3v
L9004 Pin 2 = 0v
----------------------------------------------
When I hear the CHIME, I see these signs in the oscilloscope for just a second

LVDS_DDC_CLK
LVDS_DDC_DATA
----------------------------------------------------
U9000
Pin 1 = 0v (I understand I'll never have 3v until the screen is recognized)
Pin 2 and 3=3.3v
Pin 4 and 5= 0v

Why don't it recognize the screen? …if this works perfectly with another MOTHERBOARD


Any idea what I'm doing?

[zpi]

Re: 820-2936-B Green light, chime, fan Spin - NO VIDEO

You are doing everything ok. Check continuity between L9080 pin 4 with pin 1, And pin 3 with pin2, Check continuity not with probes on L9080, but next nearest components. Lot of times L9080 goes bad, also possible that lvds socket on board is bad. But first check continuity as i said

[xalapamac]

Re: 820-2936-B Green light, chime, fan Spin - NO VIDEO

check the continuity of L9080 to the LVDS connector. Both circuits have continuity, also check the coil and the continuity is correct. I've changed the LVDS connector but continues the failure. What do you recommend?

[piernov]

Re: 820-2936-B Green light, chime, fan Spin - NO VIDEO

Internal panel doesn't show up in macOS Preferences when connected to external display?

Voltage and diode mode to ground on LVDS_DDC_CLK and LVDS_DDC_DATA?

[xalapamac]

Re: 820-2936-B Green light, chime, fan Spin - NO VIDEO

Diode mode:

LVDS_DDC_CLK = 0.595
LVDS_DDC_DATA = 0.558

The voltage of the two signals is 3.3 v.

In the oscilloscope, I see no communication pulses. Signs are always 3.3 v

[xalapamac]

Re: 820-2936-B Green light, chime, fan Spin - NO VIDEO

resistance value

R9008 = 2.18 k
R9009= 2.18 k