Strange Issue with CRT

Galaga

Hi! So I'm still working on my arcade cabinet, and I've been trying for a month now to fix this. My arcade monitor has a strange fold over issue on the top of the monitor. The original PCB doesn't have this issue so it's not the monitor. I've tried turning overscan on and off and it doesn't seem to change. Changing the resolution doesn't help either. Are there some custom overscan settings I can try or something? Thanks!

http://imgur.com/a/DGzAs

maxriptide

How did you hook up the arcade monitor to the Pi?
The picture you posted is not very clear, if the image on the top of the screen is sort of warped and you are using PI2SCART or other similar interfaces connected to the GPIO port, it may be due to the values of HDMI timings set in the config.txt file.

Galaga

@maxriptide Oops should of gave more info. I have it hooked up to a JPAC, and I have it set to a custom resolution of 320x240. I'll try to get better pictures.

Galaga

@maxriptide As you can see, the score on the top of Pac-Man is like cut off and looks messed up.

http://imgur.com/a/7TPLb

jonnykesh

Not related but you have an under voltage warning - the lightning bolt. Your PSU is inadequate.

Galaga

@jonnykesh I've actually fixed that since the picture was taken.

maxriptide

@galaga Tell me more. The JPAC requires a vga input, how did you get VGA from the PI? HDMI-VGA converter or Gert VGA GPIO adapter? and, what are the video settings on your config.txt file?

Galaga

@maxriptide I used a HDMI to VGA adapter, and here are the video settings:

uncomment to force a specific HDMI mode (this will force VGA) (that sentence has a # but I removed it because it makes the words big.)

hdmi_cvt=320 240 60 1 0 0 0
hdmi_group=2
hdmi_mode=87
hdmi_drive=2

Also when I was using an ArPiCade (a Pi to JAMMA adapter) i had the same issue.

maxriptide

@galaga the configuration is correct. Make sure to disable any overscan setting, if the problem is still present you may have to tweak some geometry potentiometer in your monitor board.

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 :(