HDMI noise/glitches when analog cable isn't connected.

[dabonetn]

Kawari large board, on 250425 MB.

There are random sparkles on the hdmi output, when HDMI is the only output connected. When both analog and HDMI connected, the HDMI is clean.

To test, power on and set background color to black. Removing the svideo plug from the switcher brings back the glitches, inserting it makes the glitches go away.

[laubzega]

Are you able to only connect GND coming from the analog cable?

[dabonetn]

Ground the video cable, and adding a termination resistor to the composite signal made no difference.

I just put the kawari into a different motherboard, and it's working without glitches. (250466 )

[randyrossi]

The HDMI is plugged into a switcher?

On Sun, Aug 28, 2022 at 2:08 PM dabonetn @.***> wrote:

Ground the video cable, and adding a termination resistor to the composite signal made no difference.

I just put the kawari into a different motherboard, and it's working without glitches. (250466 )

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[dabonetn]

HDMI is straight to the monitor.

My setup is a ASUS 24" hdmi/dvi/vga monitor, with the analog signal going thru a Extron 75C scaler to the vga input of the monitor.

[randyrossi]

Can you reproduce the sparkles and touch a jumper wire from the shielding on the micro hdmi connector to one of the GND holes on the analog RGB header? Any difference?

On Sun, Aug 28, 2022 at 4:11 PM dabonetn @.***> wrote:

HDMI is straight to the monitor.

My setup is a ASUS 24" hdmi/dvi/vga monitor, with the analog signal going thru a Extron 75C scaler to the vga input of the monitor.

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-- Randy Rossi

• "There are only two things that are hard about computer science; Naming things, Cache Invalidation, and Off-by-one errors."

[dabonetn]

I can confirm, adding a gnd between the hdmi shield and gnd on the header eliminates the issue.

[dabonetn]

Also if the gnd to shield is present on power on, the system doesn't boot. unplugging the hdmi allows boot.