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Author Topic: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)  (Read 2158 times)

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brandon

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I grew up with CRTs ( curved ones) and recently picked up a 27" flat trisync arcade monitor (WG D9800) with high hopes of building the MAME cab I've dreamed of.. and man, the geometry on this thing is garbage!  I also picked up a 27" flat Trinitron television.. it too is crap. My main gripe is scrolling games are nauseating due to the warped geometry.
 Were these flat screens ever great or do mine just need TLC?  I have serious doubts that replacing caps will fix either one of them but I'm not an expert.   Should i just ditch this monitor for a curved one?
« Last Edit: September 18, 2021, 08:39:15 pm by brandon »

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #1 on: September 18, 2021, 08:25:23 pm »
They're just more difficult to calibrate. You really need to learn what each setting does and how they all interact with each other. This includes the position and size controls which often affect the geometry pretty dramatically.

I would also make sure that all the capacitors measure at their listed values. Most flat screens came out right in the middle of the capacitor plague.

If you have a dvd player I would get a copy of the Avia II DVD, it has a wide range of patterns that can really help.

brandon

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #2 on: September 18, 2021, 08:38:03 pm »
I currently have a PC connected to the D9800 and I have a VGA to component video box to do the same with the Trinitron.  So I can load up any test pattern you can think of.  My main question was whether or not this was something I can fix with caps and tweaking the yoke, purity magnets etc.  I don't mind putting the effort into it IF it's not a monumental task but I've never messed with a yoke or magnets before.   I just want to be sure it's these issues aren't inherent in flat tubes or if I'd be better of just getting some "old school" curved tubes.  I know flat CRTs CAN have excellent geometry because I have a 20" flat PC monitor that does.  I guess when you get to large sizes like 27" it becomes more difficult. 

 Thanks for your input! :)
« Last Edit: September 18, 2021, 08:41:12 pm by brandon »

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #3 on: September 19, 2021, 01:55:52 am »
Flat screen CRTs looked like garbage when they were new.

 :cheers:
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lilshawn

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #4 on: September 19, 2021, 02:16:01 am »
hey, you try and bend an electron traveling at the speed of light 110 degrees at the neck though the envelope and then hit the same spot in a straight line a half millimeter apart. wouldn't be so bad if the turn wasn't so sharp...but then you tube would be 40 inches long.

superflat tube geometry requires some serious processing power and tuning, since you basically have to rely on a microcontroller and dedicated chips to automatically change the scan timing/duration 28,800 times a second (every line, 60 times a second.) and that's just the horizontal sweep.

it's not going to be perfect, you are going have to live with some compromises in your image unless you shell out for some serious video display monitors. the linearity is going to be a little uneven. The corners are going to be a little weird. The focus is going to be a little off here or there. it's a CRT, they aren't perfect. That's the charm of them.

you want a insanely bright, perfectly square, perfectly in focus, perfectly linear, perfectly stable picture 100% of the time, buy an LCD.

super bright, super sharp, HD displays have changed your idea of what "good" looks like.

Throw a game on there with stuff moving around, you won't notice the corner convergence is off cause literally nothing gets displayed there. play a game on there. you won't have time to notice the linearity is slightly off cause you are too busy getting killed by enemies.
« Last Edit: September 19, 2021, 02:17:48 am by lilshawn »

brandon

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #5 on: September 19, 2021, 01:34:59 pm »
I'm aware of the quirks of CRTs because like i said, i grew up in the 80s.. I'm not obsessing over grid patterns, the poor geometry is obvious in the games.  Slow scrolling games, Double Dragon, Golden Axe.. it's like I'm looking through a fisheye lens. I really don't remember it being this bad.  it has to be a flat CRT thing because as i said, I've never used them until recently.

Flat screen CRTs looked like garbage when they were new.

 :cheers:

i think you're right
« Last Edit: September 19, 2021, 01:42:56 pm by brandon »

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #6 on: September 19, 2021, 03:57:08 pm »
I was a tv engineer in the 80's and 90's.

The most common flatties in the early days were the trinitrons. I could never understand why people raved about them. Close up, as I would be as the repairman, they were awful. The convergence was never even close. And the viewing angle was very limited. From the other side of the room though this was much less noticeable.

My last CRT tv was a 36" philips matchline. It was a widescreen flattie, and the geometry was perfect in every way. The picture was superior in every way to the hitachi I had before it, even though it was older. But philips had cheated. The face of the screen was indeed flat, but the phosphers in the corners were behind about 1 1/2 inches of glass, so it was really a curved screen pretending to be flat. I never noticed this until right before I scrapped it. That explained why the thing was so incredibly heavy.

brandon

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #7 on: September 19, 2021, 04:10:00 pm »
my main issue with the geometry is the compression around the edges. it creates this weird fishbowl effect with scrolling. It's almost like this chassis was designed for a curved tube and WG just stuck it on a flat one. I emailed them and they said they only had a manual for a D9400 and every tech who knew anything about CRTs is gone.  I have a Virtual Fighter in storage with a dead curved monitor its 25-27.  I guess I'll either try to repair it (again) or see if I can use it's tube with this WG chassis and end up with at least one decent monitor.

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #8 on: September 19, 2021, 06:30:59 pm »
philips had cheated. The face of the screen was indeed flat, but the phosphers in the corners were behind about 1 1/2 inches of glass

yeah my uncle had a toshiba 34" that was a cheater screen TV. was "made for home theater viewing" or something like that. It looked great, but holy christ was it heavy. it literally took the 2 of us to lift it when he moved. a literal ton of leaded glass in the front of that thing.

brandon

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #9 on: September 19, 2021, 09:47:51 pm »
I'm find that my issue with my D9800 is the exact opposite of what it should be.  That is, compressed geometry around the edges instead of the center.  This makes me think that something else is the issue.  perhaps the chassis is designed to compensate for the distortion of flat tubes and is overdoing it.  Did any of these digital WG monitors have service menus or is it WYSIWYG? 

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #10 on: September 20, 2021, 03:27:19 pm »
oy vey

look at the datasheet for the TDA9112, the IC chip that is responsible for carrying the entire screen deflection. it has like 5 pages of waveforms showing what has to happen when you change something like the H-size or the pincushion. maybe something in there will let you know what you need to adjust to get your LCD looking fine.

as for the menu, To enter the factory menu turn the monitor off. Hold the buttons 'OSD' and 'Key +' and turn it on. be warned, you can seriously mess stuff up in here to the point you cannot see the menu to even change it back. then you are looking at an EEPROM swap.

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #11 on: September 20, 2021, 04:37:24 pm »
based on what you said, I probably couldn't put this chassis on a different curved tube because the deflection circuit or the EPROM is "programmed" for a flat tube.  I may try a factory reset and see if the previous owner screwed it up.  I found a D9200 a few hours frome but its a flat tube as well and I'm reluctant to buy another one.
« Last Edit: September 20, 2021, 10:27:24 pm by brandon »

brandon

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #12 on: September 20, 2021, 10:41:39 pm »
i made some great progress getting the geometry acceptable in the service menu but the minute i switch to a different resolution it's WAY off.  i guess these are global settings maybe? it doesn't seem to save per resolution in the service menu.. I'm starting to think I'll have to just set the monitor up for one resolution and leave it. Ditch GroovyMame  :-/
« Last Edit: September 21, 2021, 04:25:42 am by brandon »

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #13 on: September 21, 2021, 12:18:30 am »
Wow, that really is a wide screen. No wonder it gets a lot of distortion.

I've got a couple of small 21" flatscreen TVs (Sony + Sanyo) circa 2005 with component inputs that look good, geometry is perfect or at least close to. Tested with Groovymame and PCBs via GreenAntz.

Like that infographic explains, flatscreen geometry errors are a bigger issue for larger/wider screens.

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brandon

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #14 on: September 21, 2021, 04:24:34 am »
the photo uploaded weird.. it's not a wide screen. lol  i can live with the geometry now that I have more controls with the service menu. i just have to figure out why adjusting it correctly at one resolution completely ruins it on the others.
« Last Edit: September 21, 2021, 04:29:42 am by brandon »

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #15 on: September 21, 2021, 05:17:38 am »
the photo uploaded weird.. it's not a wide screen. lol  i can live with the geometry now that I have more controls with the service menu. i just have to figure out why adjusting it correctly at one resolution completely ruins it on the others.

Haha looks better now you've tweaked it or whatever :D

Why would geometry be different when changing resolutions? The things normally shouldn't be related.

lilshawn may be onto something here.

oy vey

look at the datasheet for the TDA9112, the IC chip that is responsible for carrying the entire screen deflection. it has like 5 pages of waveforms showing what has to happen when you change something like the H-size or the pincushion. maybe something in there will let you know what you need to adjust to get your LCD looking fine.

as for the menu, To enter the factory menu turn the monitor off. Hold the buttons 'OSD' and 'Key +' and turn it on. be warned, you can seriously mess stuff up in here to the point you cannot see the menu to even change it back. then you are looking at an EEPROM swap.
Check out my completed projects!


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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #16 on: September 22, 2021, 02:25:56 pm »
don't quote me, but  :laugh2: I believe all the controls are all on a GLOBAL adjustment. (IE changes the baseline adjustment of the monitor) so i don't know that you are going to be able to get a per resolution adjustment that you are looking for.

people are kinda using these monitors for an unintended purpose. generally tri and quad sync monitors do just fine... for their intended purpose... the idea being that you would put the monitor in a game...the screen would detect for that games resolution and you'd tweak the pic to look good never touch it again. it doesn't switch resolutions to work with this game and that game all the time. it's designed to work with a bunch of different games at a bunch of different resolutions but not at the same time. It's basically so you don't need to have 3 or 4 different monitors all with different specific resolutions and have to pick the right one to go into it.

yes you can load up a 32k game and have it run 32k, then load up a 15k and have it switch to that... but that's not really what it was designed to do.

i think to achieve what you are looking for, you'd have to program a custom microcontroller to interface the tda9112 through the i2c bus and have it set up to have custom screen profile for each resolution so that the 9112 can properly tweak the screen at each resolution.

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Re: Are flat CRTs crap? I bought a flat WG 9800 and I kinda hate it! :)
« Reply #17 on: September 22, 2021, 03:24:36 pm »
Yeah, I think you're right about that.  I think the "super resolutions" from CRT Emudriver are further complicating things as well.  If I tweak the image in 640x480 and then switch to 2650x240 it's way off.   Honesty, I'm not super picky even though it may seem that way.  I just want the image to not look swimmy while scrolling.  I think I'm going to delete all the resolutions except for a few.  Most everything I play is 240p+- and 15khz.  I think 640x480 and a 240p super resolution will do 99% of what I play.  I just want to get it close and tweak the width in MAME.