LG C2 screen flashes rainbow puke every few minutes

[Jon-Slow]

I have my LG C2 connected through a 15m fiber optic HDMI, things were fine for almost 2 years. Since early this year, I've noticed that sometimes my TV flashes a 1 frame rainbow, like as if the colors are inverted in rainbow. This isn't a TV issue since my PS5 output doesn't do this, and I use the TV to watch movies and shows regularly. Only happens on my PC. And doesn't seem to be a driver issue because my main monitors don't have the same issue.

 

Does anyone know what this specific issue is?

[Alex Atkin UK]

37 minutes ago, Jon-Slow said:

I have my LG C2 connected through a 15m fiber optic HDMI, things were fine for almost 2 years. Since early this year, I've noticed that sometimes my TV flashes a 1 frame rainbow, like as if the colors are inverted in rainbow. This isn't a TV issue since my PS5 output doesn't do this, and I use the TV to watch movies and shows regularly. Only happens on my PC. And doesn't seem to be a driver issue because my main monitors don't have the same issue.

 

Does anyone know what this specific issue is?

I'd assume the cable, as if its like the ones I have they can get really hot and particularly if this is happening when the GPU is under load, its going to add even more heat.  One of mine used to drop out for a second at random until I increased the GPU fans to reduce how hot the IO plate got.

 

I'd try putting a small fan blowing on the back of the GPU to see if it stops happening or maybe a short HDMI extension (assuming you can find an HDMI 2.1 compliant one) that will prevent heat from the GPU from being transmitted straight into the fibre cables shielding.

 

A more extreme method is you might be able to dismantle the plug on the cable and stick a small heatsink directly onto the chip.  Although you really need to know this is the problem first as those are hard to remove in case you have to return the cable for warranty replacement.

[MootEndymion752]

Try a shorter and/or better quality cable. The issue may be caused by interference.

[Jon-Slow]

@Alex Atkin UK Thanks, that's good inpout. I wonder if heat would make it do the one frame rainbow puke, but definetly worth a try to see if that's the case. My PC hasn't changed since I've started using this fiber optic cable and it's nott hotter. I've switched the GPU fans with 2 14cm Arctic P fans but it has only improved the temps, but it does make sense what you said about the port and the backplate. I'll try to keep that im mind.

[Alex Atkin UK]

9 hours ago, Jon-Slow said:

@Alex Atkin UK Thanks, that's good inpout. I wonder if heat would make it do the one frame rainbow puke, but definetly worth a try to see if that's the case. My PC hasn't changed since I've started using this fiber optic cable and it's nott hotter. I've switched the GPU fans with 2 14cm Arctic P fans but it has only improved the temps, but it does make sense what you said about the port and the backplate. I'll try to keep that im mind.

I mean to be fair, I cannot be 100% sure heat was the problem I just noticed it was REALLY hot to the touch and it didn't seem to happen once I cranked the fans up. 

 

Worth noting the reason that worked is possibly because it was a 4090 FE.  So it partly exhausts out the IO port which means increasing the fans inherently helped cool the HDMI plug too, whereas when I had it on slow it actually helped heat up the plug due to exhausting hotter air.  Most GPUs despite having vented IO plates, that's just to avoid turbulance, they don't exhaust air out there.

[Stahlmann]

As others have said, the problem is probably the cable. I had to use 10m active HDMI 2.1 cables in the past and it was very hit or miss, and tbh, none of the dozen or so cables I tried gave me a 100% reliable connection. Some were pretty stable, but none were able to be as reliable as a certified standard 2m copper cable.

[Jon-Slow]

22 hours ago, Stahlmann said:

As others have said, the problem is probably the cable. I had to use 10m active HDMI 2.1 cables in the past and it was very hit or miss, and tbh, none of the dozen or so cables I tried gave me a 100% reliable connection. Some were pretty stable, but none were able to be as reliable as a certified standard 2m copper cable.

This is a fiber optic cable mind you. I also didn't have this issue for almost 2 years with the same setup. But it is possible that the cable has degraded or something similar.

Waiting to do more tests.

[Stahlmann]

5 minutes ago, Jon-Slow said:

This is a fiber optic cable mind you. I also didn't have this issue for almost 2 years with the same setup. But it is possible that the cable has degraded or something similar.

Waiting to do more tests.

Fiber optic cables can be very fragile. Maybe you tripped over it ot something and cracked some fibers. All the 10m cables I used were also active fiber.