CRT PAL screen flicker (RCA/Composite)

Varno

Hello,

I bought an old 14" CRT monitor to replicate that old retro feel when using RetroPie. I connected my Raspberry Pi 3 Model B to the CRT via a RCA cable from Adafruit with a SCART adaptor at the end. I changed to PAL in the config.txt and adjusted the overscan settings, but I still get a lot of horrible flickering. It hurts my eyes and it's not really playable. I've seen a lot of posts commenting on the flickering, but with no real solutions.

Any help is much appreciated !

Best,
Daniel.

Jakob Holz

Have you tried changing it to the American protocol (NTSC)?
I heard tough it provides a lower resolution it has less flickering.

Anyways I have a similar problem, have you solved your problem and if yes how?

edmaul69

@Varno @Jakob-Holzim not sure if this works for pal but look at user "popcornmix" he has a fix that allows you to output 320x240 to fix the 480i flicker. Look for his post with a download link

https://github.com/raspberrypi/firmware/issues/683#issuecomment-283179792

Jakob Holz

@edmaul69 Thank you very much.

Jakob Holz

@edmaul69 I have installed the firmware and changed the config via the SSH protocol.
First I experienced an issue with the synchronization signal but after changing the SDTV mode to 18 (progressive PAL) I got that fixed.
I'm still experiencing severe flickering though and unfortunately the firmware wasn't able to fix my problem.

Thank you anyways and please keep me up to date if you catch something new.

edmaul69

@Jakob-Holz can you show me a link to where the progressive modes are??

edmaul69

@Jakob-Holz what happens if you set

sdtv_progressive_scan=2

You might have to remove sdtv_mode=18 if that is what you had set

Jakob Holz

@edmaul69 My config currently looks like this:

sdtv_mode=18
sdtv_aspect=1

Synchronization works but the flickering is still there.
When you scroll down the forum link you sent, you see popcornmix describing the different commands.
I only know as much as he has said there.

edmaul69

@Jakob-Holz remove the

sdtv_mode=18

And add this

sdtv_progressive_scan=2

And see what happens

Jakob Holz

@edmaul69 Still flickering hard, but thank you.

edmaul69

@Jakob-Holz im thinking there is a pal issue here.

Jakob Holz

@edmaul69 NTFC is the same

Jakob Holz

Well after revisiting my old settings and comparing it multiple times with my current I can clearly tell that the firmware from popcornmix with "sdtv_progressive_scan=2" in my config definitely improved the flickering but there is still quiet some over.

edmaul69

@Jakob-Holz said in CRT PAL screen flicker (RCA/Composite):

@edmaul69 NTFC is the same
When you tried ntsc did you change this:

sdtv_progressive_scan=2

To this:

sdtv_progressive_scan=1

Jakob Holz

@edmaul69 Well I think its best to tell the whole story to make sure I didn't mess up somewhere else I'm not using an old CRT monitor. I'm using a hacked 3.5-inch car monitor (PAL/NTFC) which I bought on Amazon for about 15€.

Link: https://www.amazon.de/gp/product/B0056WJP1M/ref=oh_aui_detailpage_o00_s01?ie=UTF8&psc=1
(German store, but they are all the same)

It has 2 composite video inputs and is designed to work with 12V DC from a car battery. But I found that the screen itself operates with 5V DC. So I shorted the step up chip on the board and connected a 5V pin from the Pi3's GPIO directly to the output of said chip. The ground of the monitor is also connected to one of the Pi3's ground pins of its GPIO. I soldered the video signal input 1 of the monitor to PP24 on the back of the Pi3.

edmaul69

@Jakob-Holz ok you need to undo everything you have done. This was a fix for crt monitors. There are tutorials for small lcd monitors on the pi. You do something completely different. It is really simple too. I believe you just set a dtoverlay in the config.txt. I forget though. It was really simple. However the flickering could be a problem with how you shorted it out or the lcd just wont run on 5v properly.

edmaul69

@Jakob-Holz i have a theory. You need to shorten your shorted out wire. The red one and get it as far from those capacitors as possible. Im pretty sure thats your cause of the flickering as i have had that issue myself. And if it still flickers, use a thinner wire for that jumper.

Jakob Holz

@edmaul69 Ok I feel like a total idiot right now.
But thank you so much for your kind advice.
But isn't it a bit strange then that it somewhat helped my problem?
I was about to undo all my config changes & my 5v shorting and power it with 12 from my lab bench power supply.
But I will try to shorten the shorting and maybe shield it and ground the shielding, would that maybe help?
By the way, doesn't the video composite video signal need a ground potential?

edmaul69

@Jakob-Holz shortening it, and getting it away from the caps should do the trick. Shielding it isnt neccessary. If you need to you can twist your composite and ground wires going to the pi if you are still having video issues.

edmaul69

@Jakob-Holz also remove that point on the 5v solder joint. You could be creating a spark gap with it pointed right at the ground.