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Screen flickering with Arpicade

Posted: Fri May 22, 2020 11:21 pm
by rickshred
Hi, I'm having an issue with an arcade setup. I have the Arpicade running on a PI 3B with version 3.84 installed. I have had it running on an older NBA Jam cabinet and it works perfectly. I love it! I purchased a much newer (2009) Showtime cabinet. This more modern PCB is still using Jamma, and it has a Makvision monitor (tri mode) with a replacement chinese 23" tube that has only been used for 1 year out of the box (NOS). It looks great and works only in standard res mode for for some reason when connected to the PCB. Well, I can't seem to get the arpicade to work with this new setup without either a flicker in mode 6 (only flickers with the vertical games and the attract mode screen), or in mode 8 the attract screen is a little jumbled and the vertical games are half the normal width (not much fun to play :roll: . The horizontal games work flawlessly in either scenario, it's only the vertical games and attract screen that are giving me a problem. Also, I have tried changing the resolution to mode 1, and it works perfectly in either hor. or vert. but alas, the vga output from the arpicade isn't very sharp, I'm assuming because of conversion to VGA from CGA. Any help would be appreciated. Ultimately, my goal is to port my jamma switcher from my original nba jam cabinet to this new one and be able to run original showtime from the PCB and then switch over to the arpicade for all the other games. All on a glorious CRT. Thanks for your help!

Re: Screen flickering with Arpicade

Posted: Sat May 23, 2020 8:45 am
by dee2eR
Sounds like your newer monitor doesn't handle 480i very well. The horizontal games are switching to 240p so they look fine. Unfortunately as you've found using the whole system in 240p is a bit of a compromise for the menus and any rotated (or 480i originally) games.

This is a bit of a hard one... NBA Showtime is not emulated properly in MAME and I don't have the PCB so I'm more familiar with the Dreamcast version of NBA Showtime. Is the arcade version a low res game? It's low res on DC but can be patched for VGA (which looks better on DC)... If NBA Showtime PCB is low res I would consider swapping the cabs monitors so you have the one with the nicer handling of interlacing. Depending on our plan for the other cab that may or may not work for you though. While I don't actually have any multi-res monitors I have heard they often arn't as good at low res as a dedicated low res monitor (maybe nothing to do with interlacing though, there's pretty big variation in how it can look on any particular monitor).

When you say converting VGA to CGA (when you mentioned trying mode1) are you using some sort of scaler or something? Or are you just talking in the software? If you have some other hardware in the video chain it could be effecting the image, hard to say as I don't know if you do...

There are some config changes you could make to sharpen up the high res image, although they may not be consistent across all the emulators. The default high res settings are setup to make LCDs look OK, they may not be the best settings for a high res CRT. No matter what you do though they won't look as good in high res as on a low res CRT as that's what the games were intended to be used with.

Another possibility may be to run the system in 240p and change the menu theme, some will suit 240p better than others. You could even modify the launchers/res switch script so the system swaps to 480i for vertical games to get the screen real estate back for rotated stuff. It's a bit of a compromise but if the monitor you want to use doesn't look great interlaced...

Re: Screen flickering with Arpicade

Posted: Sat May 23, 2020 4:35 pm
by rickshred
Ok, some things to digest here. You may be right that the newer monitor doesn't handle 480i very well. It sounds like the flicker must be related to the interlacing, because in widescreen, we are at 480p it sounds like. It looks great in widescreen. I really have 2 issues here, but I was only trying to solve the one directly related to the Arpicade. Issue, 1, is getting the arpicade to display properly with my setup. Issue 2 is that my PCB doesn't work in Medium resolution, which the game was DESIGNED for, so that's a big disappointment.

Back to issue #1. Perhaps you are right about the low res issue and the Makvision chassis with the new Chinese tube combo doesn't really support interlacing in low res very well. The flicker isn't terrible, but it's what I wanted. I'd like it to look great, since that's the whole reason I'm sticking with a CRT in the first place! A little clarification on the emulation to VGA. I'm talking about the software. I changed the mode in Arpicade to VGA (mode 1) and plugged the DCA(I think that's what it's called) from the arpicade into the monitor with a VGA cable, switched the monitor to accept high res (1K ohm 3v vs 75 ohm 1V to get to 31K) and it worked just fine- no flicker. But then I lost detail on the Mame games. The images look much less sharp. I will upload a picture. I assume that's because the arpicade is converting the image to work in VGA, rather than CGA, at 15K which it was designed for. I could have this be a permanent solution, but then it is a compromise, which I didn't want to make. I might actually prefer the slight flicker in low res vertical games CGA over the lost detail in VGA on every game...

OK, so a little detail on issue #2, just so I can get it all out there (this journey was not supposed to be quite this painful but in the end it's all for the hobby, right?). Showtime/blitz 99/Hangtime are all designed for Medium res. This is the entire reason I bought the new cabinet with the working PCB (showtime) so I could have the best of both worlds: a working medium res showtime and then all the original mame games in standard res. Also the unit has a tri mode monitor so in theory it was supposed to work. When I pulled up the service menu on the showtime PCB, it showed by that it was in low res. I switched it to medium res with a dip switch, and the whole thing freaked out. I will upload a short video if this forum will let me. So obviously I have a problem in medium res. I don't know if it's the video board associated with the PCB, or some other problem related to the mismatched monitor/tube. either way, it's a big problem. I also am not sure how to isolate this issue, since I can't convert medium res from the PCB to VGA to test the video card by connecting the PCB to a LCD monitor and see if I can get medium resolution to work outside of the CRT. I might buy a conversion board that supports CGA medium res to VGA for $25 on ebay to test that theory...

Which brings me to my final thoughts about options. I'd like to have the CRT setup work out, but it seems quite difficult at this point. I could

#1. switch monitors with the original NBA Jam cabinet that I started with. This has a standard res monitor and it works fine. I'm sure it's 25 years old or something, who knows. It looks fine, and I had the chassis repaired a few years ago... The downside to this is that I will never get hangtime in medium res. But the NBA jam monitor is 25" whereas the new cab with the chinese tube is only 23" (weird size).

#2. Keep the new setup with the new cab and figure out how to fix either the monitor/tube/video board problem in Medium res and compromise the Mame stuff with the arpicade in either low res with interlacing, or vga with fuzziness.

#3. Put an LCD in the hangtime with a medium res to VGA conversion board for the showtime PCB and the arpicade in VGA mode. this has some big compromises as well. I can probably get a 26-28" LCD in there, but then I'm widescreen, and upscaling and loss of detail etc.

I'll see what I can upload and I appreciate any thoughts in case you have any suggestions. Did I mention that I love the arpicade?

P.S. looks like I can't upload the short video of the monitor/cab freaking out making a ton of noise in medium res. Also can't upload pictures, as the smallest format I could get it into at 500KB was too large.