Strange Issue with CRT

Galaga

@maxriptide I've tried messing with the overscan settings but nothing would change. And when I tried adjusting the monitor, the picture would move but it would still look cut off. It never did this on the original PCB so I'm guessing it's the Pi being stupid. Oh well :(

edmaul69

@galaga does your monitor have a switch somewhere on the board that lets you switch between 15khz and and something like 24 or 31khz on it? It could be anywhere on the board or if your controls are on a seperate board it could be on that.

Galaga

@edmaul69 The monitor is definitely 15Khz, and the JPAC is set for that too.

akafox

I use and old CRT on for my raspberry pi 3 here is my settings:

This is setup of a NTSC crt tv your settings will differ based on your country
The bolded info is one that solved my problem
This is for crt TV NOT an arcade monitor I am not responsible for any damages!

(More here: raspberry pi config.txt)

#uncomment for composite PAL
sdtv_mode=0
sdtv_aspect=1
overscan_scale=1

#uncomment this if your display has a black border of unused pixels visible
#and your display can output without overscan
#disable_overscan=1

#uncomment the following to adjust overscan. Use positive numbers if console
#goes off screen, and negative if there is too much border
overscan_left=10
overscan_right=10
overscan_top=-8
overscan_bottom=-4

#uncomment to force a console size. By default it will be display's size minus
#overscan.
framebuffer_width=720
framebuffer_height=480

edmaul69

@akafox he has to do the 320x240 mode not 640x480 because of his 15khz arcade monitor

edmaul69

@galaga can you look and see if any caps are blown? I think this might be a problem with the monitor and not the pi. Even if the original game board you used didnt show an issue. Its been a good many years since i worked on arcades so i am fuzzy on the cause but it is something i have seen before.

akafox

@edmaul69 I am aware of that...I just didn't know the resolution settings for the monitor.

Question..will the pi burn out a arcade monitor like it will an old crt TV?
Or is an arcade monitor more "like a PC monitor"?

Galaga

@edmaul69 I haven't taken the chassis out but I can't see anything wrong. I've never replaced caps on anything before so doing a cap kit is really scary lol. You think I should take it out anyways?

Galaga

@akafox I will try adding the overscan parts in config.txt and see what happens.

maxriptide

@akafox while pc monitors (multisync monitors) are usually protected against out-of-spec signals and may display a message such as "signal out of range", an arcade monitor may be damaged if an out-of-spec signal is sent to it. If you see a scrambled image on your monitor you'd better switch it off as soon as possible.

Adding overscan will prevent you from getting a pixel-perfect image.

Galaga

@akafox said in Strange Issue with CRT:

overscan_left=10
overscan_right=10
overscan_top=-8
overscan_bottom=-4

I added those lines in config.txt and it made no change :(

Galaga

@akafox Actually I added the framebuffer lines under the overscan lines (used 320 and 240) and it fixed the issue! But only in the terminal...

Galaga

Any suggestions?

akafox

strange..are using advmame? you might have to tweak the settings in the admame.rc

Galaga

@akafox No, RetroPie is completely ignoring the config.txt settings...

Galaga

Ok I think I finally fixed it to the point where it doesn't make me angry. I decided to try someone else's config.txt as mine was cursed or something :P I went here: https://www.dropbox.com/sh/6hdpa7893c3ked1/AABCXqUHjXI-C3PUdcq4f8jya?dl=0 and downloaded the "custom_res" config. I renamed it to "config.txt", changed the resolution to 320x240, and added some custom overscan numbers. The lines are still there, but they don't affect the text and only appear on a black screen. I'm sure I could go further and 100% fix it but right now I'm happy. Whew!