asus k56cm missing resistor

[jasko_jacker]

Hi, HDMI hot plug pin 19 HDMI connector: This pin if I understand well send a signal to a transistor gate to flow a tension from 3VS to pch . The signal on pin 19 HDMI is not direct but is managed by two resistor.
In asus g73 there are two resistors but I don't understand the function of D4802 and how the motherboard manage the hot plug signal, probably from GPU

I

[piernov]

Re: asus k56cm missing resistor

On G73JW, I think D4802 is only acting as a clamping diode. Seems like the HDMI port is driven by the MXM video card only.

[jasko_jacker]

Re: asus k56cm missing resistor

Ok,
but on k56cm can I use 1 K resistor ?
Pin 19 on HDMI connector is an output signal, right ?

[BlueMidnight]

Re: asus k56cm missing resistor

Yes, on the G73JW, D4802 clamps voltages that are less than ground (negative) or higher than 3V.

The monitor provides 5V on pin 19 so the board knows when a monitor exists. The larger resistor to ground (10K on the K56CM) makes sure the pin is not left floating (or else it may trigger a false detection). And the smaller series resistor being 1/10 of that value (i.e. 1K) should be just fine. The resistance can't be too much higher than that, or the transistor will never turn on

The transistor is used to convert the 5V signal to a 3V signal for the the rest of the board (PCH and EC).

[jasko_jacker]

Re: asus k56cm missing resistor

I have used a 1k resistor and now the mosfet reach the treshold voltage and send +3VS voltage to PCH, but the hdmi don't work.
I have repaired this motherboard after another technician fails ; I don't know what he did but it seems that he changed the hdmi port. I checked all pins and all seems ok but there are two resistors:
R4821 (HDMI_CLK_C -> HDMI_CLK_R) in place
R4822 (HDMI_DAT_C -> HDMI_DAT_R) missing
I think that R4822 is required because I don't see any connection for this data line.
Unfortunately, the boardview is in .ASC format and it is not known whether a component must be placed or its value, based on R4821 I think that R4822 must be the same.

[BlueMidnight]

Re: asus k56cm missing resistor

Yes, both resistors are required, and there is no reason why they wouldn't be the same value.

[on/off]

Re: asus k56cm missing resistor

Hope this helps.
This my interpret by base from Asus N73SV, but need confirm from BlueMidnight and Piernov is correct or not.

Actually on page 23 and 48 only.

Red rectangle mark on schematic is part from your BV K56CM.
Sadly on HD image K56CM R4821 and R4822 covered by black tape.


Link HD image:
https://drive.google.com/drive/folde...EU1WVlKWmtJQnM
Credit to [tsurik] Nikolay Tsurka

[EnricoS92]

Re: asus k56cm missing resistor

I have used a 1k resistor and now the mosfet reach the treshold voltage and send +3VS voltage to PCH, but the hdmi don't work.
I have repaired this motherboard after another technician fails ; I don't know what he did but it seems that he changed the hdmi port. I checked all pins and all seems ok but there are two resistors:
R4821 (HDMI_CLK_C -> HDMI_CLK_R) in place
R4822 (HDMI_DAT_C -> HDMI_DAT_R) missing
I think that R4822 is required because I don't see any connection for this data line.
Unfortunately, the boardview is in .ASC format and it is not known whether a component must be placed or its value, based on R4821 I think that R4822 must be the same.

Hi,

I have a K56cm, both resistors are present (under the black tape under the heatpipe) and they are 0 ohm.

[jasko_jacker]

Re: asus k56cm missing resistor

Thanks All for the support
I replace the missing resistor with 0 ohm and the hdmi works great-