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Author Topic: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver (SOLVED!)  (Read 6275 times)

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BumbleChump

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Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver (SOLVED!)
« on: February 25, 2020, 01:00:33 am »
(Edit: I've solved the issue! See my last post! Woohoo!)

Hi Everyone,

New user, but I've been participating over on Arcade Projects.com restoring an Astro City. Nice to meet all of you!

https://www.arcade-projects.com/forums/index.php?thread/11781-astro-city-restoration-and-monitor-fix/

So I've got CRT Emu driver working on my Nanao MS8 29FSG, but there's pretty bad artifacting on everything. Even the desktop at 320 x 240 has it. I'm using a Radeon HD 5770 with Windows 10 and a JPAC.



There's quite a lot of white spots on the right side of the pixels. It's noticeable pretty much everywhere, especially on the right side of Sakura's skirt and hair, as well as the background. I know it's not the monitor because this does not happen when I have the Neo Geo (real hardware) plugged in. The chassis and PSU have been completely recapped and fixed as well. Here's what I've tried.

Various Monitor presets, Generic, Arcade 15khz, Nanao MS9, etc. Different games, Super resolutions, original resolutions, I can't seem to figure it out.

Would I need to create a monitor preset for the Nanao MS8 29FSG? I've been doing a lot of reading on CRTs. Learning about Front Porch, Back Porch, stuff like that.

Thank you in advance! And I'll be sure to share anything I learn about the MS8 29FSG, as it doesn't seem to be a very common monitor.
« Last Edit: May 01, 2020, 03:59:17 pm by BumbleChump »

lilshawn

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #1 on: February 25, 2020, 04:42:08 pm »
The MS8 is actually a very popular monitor....just not outside of Japan.

your issue looks like a signal problem not a monitor problem....and like you say, real hardware doesn't exhibit this issue... which basically eliminates the monitor as a source.

i'd look into how your PC is connected and how the ground from the VGA cable is tied to the computer. VGA has several grounds and some cables might only use one for ground where your videocard might be expecting more. try running "nokia test" or "eizo monitor test" and see if just particular color is doing it... or if it's them all. see if there is some kind of graphics smoothing or something going on in your videocard driver.

it's not much, but it's something to start with.

BumbleChump

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #2 on: February 25, 2020, 07:59:40 pm »
Thank you! I'll definitely look into the grounds for my setup, as well as those tests you mentioned.

Will report back soon!


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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #3 on: February 28, 2020, 02:13:28 pm »
I've tried various things, but none of them worked. There's also a small spark sometimes when connecting the JAMMA to the computer. The grounds and video ground on JAMMA are the connections causing the spark, so I think I have a ground loop. All the equipment is ultimately grounded at the same point, so I need to figure out how to reduce or remove the ground loop.


buttersoft

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #4 on: February 28, 2020, 10:12:30 pm »
To digress, because i have no idea what's causing your issue, the MS8's can be a little sensitive in other ways too. Lilshawn, do you have any idea if the MS8-29FSG is going to have the same issues as the one's the MS8-26SE does, that i linked to a while back?

Relevant posts are by Jomac in the linked thread:

https://www.aussiearcade.com/forum/aussie-arcade-sponsor-s-trading-forum/arcade-pinball-and-amusement-machine-sponsors/jomac/70010-hold-issue-on-ms8-26se-chassis

lilshawn

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #5 on: February 29, 2020, 04:00:20 pm »
they are the same monitor (same electronics) ... just a different tube.

BumbleChump

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #6 on: March 02, 2020, 12:29:48 pm »
Figured out some more things, but no closer to solving the issue.

Just to rule it out, I disconnected the ground from the Astro City, and it didn't change anything. (Wasn't planning on keeping this fix, I know it's dangerous)

Tried VGA cables with ferrite chokes, tried powering the jpac with a battery pack in case the vga and usb were causing a ground loop?

Most interesting though, I hooked up the jpac to my super gun, which is connected to a PVM, and the image is perfect.



But if I hook the jpac up to the Astro City, it looks like this. Lots of white spots in areas of high contrast change, like the right edge of her ponytail, or all over her pants. Her belt is also perfectly clear on the PVM, but it's a mess on the Astro City.



Gonna continue to experiment until this is solved....
« Last Edit: March 02, 2020, 12:44:27 pm by BumbleChump »

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #7 on: March 02, 2020, 04:20:30 pm »
Did some more research. The actual term for what I'm seeing is "Edge Enhancement" "Unsharp Masking" or "Ringing Artifacts"

https://en.wikipedia.org/wiki/Edge_enhancement

https://en.wikipedia.org/wiki/Unsharp_masking

https://en.wikipedia.org/wiki/Ringing_artifacts

The Unsharp Masking article says it's generally a filter that amplifies the high-frequency components of a signal. I know the jpac amplifies the video signal to arcade levels, so maybe that's playing a part in this? PVMs aren't picky and accept a lot of signals, so that's possibly why it's working on the PVM, as opposed to the picky MS8 29FSG.

Still researching....


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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #8 on: March 03, 2020, 12:51:44 am »
If you have a spare gpu, i would try it, just to rule out the gpu.
I've seen very strange issues happening due to bad gpu.

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #9 on: March 03, 2020, 05:01:15 pm »
Ok I just ordered a new GPU. I didn't know how cheap these were! Got an HD 6450. My current card, the HD 5770 is a gaming card with an 8 pin power input. Maybe that was too much in some way for this, which is what was causing the ringing? At least, that's what I'm hoping.

Thanks for the tips so far, everyone!

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #10 on: March 04, 2020, 07:30:31 am »
Well, I've seen very weird defects on cards that have been overclocked in the past. It won't come to me as a shock if this turns out to be a defective gpu.
Do you know if your gpu has worked correctly or did you try crtemudriver straight away after getting the card?

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #11 on: March 04, 2020, 01:01:38 pm »
Actually, I got this card brand new back in 2009 for my gaming computer. It's always worked fine as far as I know. I never overclocked it or did anything weird to it.

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #12 on: March 08, 2020, 11:16:11 pm »
I tried the other graphics card, no difference at all.

So I measured the voltages across RGB and Sync on my Neo Geo, each color is about 0.49v, and sync is about 3.3v. Lines up with what I've read online.

But the JPAC is outputting the following:

Red= 0.18v
Blue = 2.14v
Green = 1.31v
Sync = 3.08v

This can't be right, can it?? Anyone have some insight?

Zebidee

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #13 on: March 09, 2020, 07:06:36 am »
Try isolating/bypassing your JAMMA completely and feeding video signals directly into the monitor. Signal should be weak but visible - see if you still get artifacting. If the artifacting disappears, then it looks like your JAMMA or maybe the jpac is the source of your problems.

You shouldn't be getting any sparks when connecting JAMMA, even when power is connected (this is bad form anyway, you might cause some damage). Video signals are very low voltages. There are 12v & 5v available on JAMMA if you have a DC power supply connected inside your cab, but even then sparks would be unusual and alarming. I suspect that you have some problem with the grounds in your JAMMA connector.
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BumbleChump

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #14 on: March 10, 2020, 03:35:11 pm »
Thanks for the info. I would bypass the Jamma, but my monitor doesn't have a VGA connector. I could splice it up, but I'm going to try another thing first.

I also realized it's actually ghosting, not artifacting. When I switched the screen to 640 x 480 @ 30hz, I noticed the mouse cursor was clearly ghosting as in, multiple mouse cursors appearing.

More reading has led me to find this:

"A separate video ground connection to the monitor can help to maximize picture quality, so many arcade
cabinets are wired this way. Pin 14 of the JAMMA standard is allocated to 'video ground', which is this
separate ground connection. However, many classic-era arcade games don't have a separate video ground
connection: they assume that the monitor is connected to the same ground as everything else. These games
need a connection from video ground to power ground to work correctly in a JAMMA system. "

https://martinjonestechnology.files.wordpress.com/2014/11/jamma-fingerboard-instructions-v1-1.pdf

I also found someone who had a similar issue. They replaced their entire Jamma harness and got ghosting issues with their Naomi. He ended up cutting a ground from the "video wire" (I'll assume video ground) to solve the problem.

https://www.arcade-projects.com/forums/index.php?thread/5589-strange-ghosting-after-jamma-connector-change/&pageNo=1

On top of all of this, the wiring diagram for a New Astro City shows that the video ground does not connect to the others grounds.

http://1.bp.blogspot.com/-kIQl10gvTe0/UmZud3tXqxI/AAAAAAAACcs/mJXdU4cbKQ4/s1600/Sega+New+Astro+City+Wiring+Schematic.png

If I remember correctly, when I tested continuity on the cabinet's Jamma harness, the video ground and general ground were connected. I'm going to break this connection and see if this helps. If it doesn't, then I'll splice the computer's VGA directly to the monitor.

BumbleChump

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #15 on: March 11, 2020, 02:55:04 pm »
Try isolating/bypassing your JAMMA completely and feeding video signals directly into the monitor. Signal should be weak but visible - see if you still get artifacting. If the artifacting disappears, then it looks like your JAMMA or maybe the jpac is the source of your problems.

You shouldn't be getting any sparks when connecting JAMMA, even when power is connected (this is bad form anyway, you might cause some damage). Video signals are very low voltages. There are 12v & 5v available on JAMMA if you have a DC power supply connected inside your cab, but even then sparks would be unusual and alarming. I suspect that you have some problem with the grounds in your JAMMA connector.

Wasn't able to try this yet since I realized I need a way to combine the VGA syncs without using the Jpac. I also confirmed that the video ground and general ground are not connected in the jamma harness. I'm going to try something weird though, inspired by this thread:

http://forum.arcadecontrols.com/index.php/topic,158700.40.html

He was able to solve his problem by having a lowpass filter in the chain, so I'm going to use a PVM in the chain. It has outputs for every input, and I'm hoping it will clean up the signal?

GPU>VGA>JPAC>Super Gun>SCART/BNC>PVM>BNC spliced to Jamma harness

By the way, did you ever make that low pass filter for that guy, Zebidee? Did it work out?

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #16 on: March 11, 2020, 08:31:29 pm »
I don't think using the PVM will do anything. The PVM has passive pasthroughs, the use of which removes the 75R termination required by analog video equipment. The last monitor in the daisy chain has the 75R terminations. Arcade monitors do not often use or require these terminations. The lack of them might make the image on the PVM brighter but ghosted a little.

It's worth a try because everything that's not going to hurt is worth a try, but i'd be surprised if you see any positive change.

Can you not output composite sync from your video card directly using crt_emudriver? If not, a 500R resistor and then 1K pot in each sync line, then combine, should give you working sync. Just dial the pots around.


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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #17 on: March 11, 2020, 11:47:10 pm »
A warning note here about arcade monitors and grounds: Be aware that arcade monitors, at least older ones, typically use have a "hot" chassis and require an isolation transformer to physically isolate the chassis from the normal electrical wires. Effectively they have a "local" ground at this point and it *must* be separate from any mains or other grounds. So whatever you do don't ground the chassis to anything else. In summary it can create a situation where you are more likely to be electrocuted, and you may zap something you don't mean to.

Now having said that, your video signals terminate on the "cold" side of the chassis, which means it is OK for your video grounds to be connected all the way through from the chassis to the JAMMA to the PCB/PC etc; and in fact they should be, so this is definitely something to check. You can easily check continuity end-to-end using a cheap multimeter on the diode setting.

Wasn't able to try this yet since I realized I need a way to combine the VGA syncs without using the Jpac.

I would never argue with Buttersoft because he is wise and knows his stuff - but I say you'll be fine just twisting the H&V sync wires together for the purposes of using a VGA breakout cable to test the monitor (assuming that your PC outputs negative sync on both H&V - which is the ATI default so it will be unless you've changed it). Arcade monitors expect higher voltages than TVs so no need to pull it down.

However, putting resistors on sync lines when making cables for TVs is prudent as the standard for TV sync is 0-1vpp, whereas for PCs it is 0-5vpp, so pulling the voltage down makes sense (Full disclosure: I've made plenty of VGA-SCART cables with no resistors and used them with lots of TVs, still am using them, have been for years and years, never had any problems, but maybe it's because my TVs are better-quality ones. If I was to make a new cable tomorrow I'd probably try a 680ohm or 1k ohm resistor on the sync, can't hurt).

I'm going to try something weird though, inspired by this thread:

http://forum.arcadecontrols.com/index.php/topic,158700.40.html

He was able to solve his problem by having a lowpass filter in the chain, so I'm going to use a PVM in the chain. It has outputs for every input, and I'm hoping it will clean up the signal?

By the way, did you ever make that low pass filter for that guy, Zebidee? Did it work out?

Unfortunately life and injuries got in the way after I posted that and I've been finding it hard to get back to my hobby (or even to get into my shed) for the past year or so. However I did eventually make that little video amp circuit as I was attempting to improve a blooming issue I was having with a cheap Chinese arcade monitor - I was using an Ultimarc video amp and it seemed to be boosting the video signals too much, making the picture "bloom" heaps whenever something bright happened. It worked, but was a bit ugly. Unfortunately something else came up and I never got to make a second one for Sublevel (or even to take that particular arcade cab project much further - it is still on-hold).
 
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BumbleChump

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #18 on: March 12, 2020, 12:14:59 pm »
Can you not output composite sync from your video card directly using crt_emudriver? If not, a 500R resistor and then 1K pot in each sync line, then combine, should give you working sync. Just dial the pots around.

Oh duh, I forgot about that. I can definitely just splice it to the Jamma. Thanks for the reminder. Also I'll wait on the PVM thing. Gonna make a low pass filter instead.

Unfortunately life and injuries got in the way after I posted that and I've been finding it hard to get back to my hobby (or even to get into my shed) for the past year or so. However I did eventually make that little video amp circuit as I was attempting to improve a blooming issue I was having with a cheap Chinese arcade monitor - I was using an Ultimarc video amp and it seemed to be boosting the video signals too much, making the picture "bloom" heaps whenever something bright happened. It worked, but was a bit ugly. Unfortunately something else came up and I never got to make a second one for Sublevel (or even to take that particular arcade cab project much further - it is still on-hold).

As far as I know, Astro Citys don't have an isolation transformer, and the monitor is not supposed to be grounded with the other metal parts in the cabinet. And that's a bummer on the injuries! Hope it's better now.

I was wondering though, if you use that video amp you made with a Jpac, isn't that amplifying the signal twice?

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #19 on: March 12, 2020, 09:58:43 pm »
As far as I know, Astro Citys don't have an isolation transformer, and the monitor is not supposed to be grounded with the other metal parts in the cabinet. And that's a bummer on the injuries! Hope it's better now.

Embarrassingly, I used to own an Astro City with that monitor (loooong time ago). I can't remember whether it has an ISO or not (pretty sure there is one). If there is no ISO, then there would be a bridge rectifier on the chassis power supply that eliminates the strict need for one, although they are still desirable as they make the monitor much safer (much less likely to electrocute yourself). To complicate things, cabs use step-down tranformers to get the right voltage, which may also be an ISO transformer even if they don't technically need an ISO. But for your purposes this doesn't really matter -  just don't ground the monitor chassis to anything else (video signal exception).

Thanks for the good wishes - Injuries all better now, I really appreciate walking!

Quote
I was wondering though, if you use that video amp you made with a Jpac, isn't that amplifying the signal twice?

I wasn't using a JPAC then - I was running the signal directly from PC to arcade monitor using a VGA breakout cable->amp->monitor. The composite sync was achieved by simply twisting together wires from pins 13&14, no resistors, directly PC-VGA -> monitor. Very stable. The home-made video amp only processes the RGB signals, does nothing with the sync.

On stable csync - I've found csync via CRT_emudriver to be less stable. A possibly related problem with using csync from CRT_emudriver is that if you have pin 14 (vsync) connected it will create interference on sync, so you if you've made cables with pin 14 connected you'll have to undo and disconnect it. After experimenting a few times I decided it wasn't worth the bother. All my cable are made with 13+14 connected so I'll just stick with that unless I have to change for some reason.

People make such a big deal about csync. If you really want to get fussy about csync then you can get some LM1881 chips and make your own sync combining circuit quite cheaply with a few capacitors and resistors, but you really don't have to bother in this case as twisting 13&14 together and putting them into the sync input on your monitor will be all you'll need.
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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #20 on: March 13, 2020, 11:33:03 pm »
All good to know. My monitor chassis isn't grounded to anything for sure. And dang, walking!? Glad to hear you're better now.

I've done a few things now. I connected the VGA from the computer directly to the monitor by twisting the syncs together like you mentioned. No JPAC. Here's some comparisons between raw VGA and JPAC. The first image is raw VGA, the second is JPAC.









Blegh, Bison's gums are a mess. Based on this, it looks like the computer is outputting those white ringing spots even without the JPAC. It's especially noticeable around the edges of M.Bison's cape. The JPAC is just amplifying the ringing. So I made a low pass filter at 220 microfarads and 75 ohms and I get this:



The image just turns blue? You can faintly see the icons on the computer desktop. I made sure there wasn't any wire issues with the red or green. As I removed each capacitor, it restores that color. If I remove all 3 caps, the image looks normal. I also tried higher and lower capacitances. The higher capacitance didn't change anything. But if I went lower, the image would become slightly less blue. I went down to 0.1 microfarads and it looked like someone smeared the screen like a hot knife on buttered toast. I also tried flipping the capacitors +/-, but that didn't change anything.



I connected the input red, green, and blue to the left of those resistors, and the output RGB to the right of the resistors. I cut a very heavily shielded VGA cable in half, and spliced this low pass filter into it. All the capacitors were grounded to the main ground. I tried video ground too, but nothing changed. (ignore that one flipped capacitor in the photo)

I'm thinking I need to "clean" the signal from the computer with some external device, I'm just not sure what yet. And I'm sure some might think that the image looks fine, I'm just being picky. And you're right. But the Neo Geo outputs a fantastic signal with no ringing so I want to get that from the computer as well!

Thanks again for the help so far, will continue to figure this out.

« Last Edit: March 13, 2020, 11:38:45 pm by BumbleChump »

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #21 on: March 14, 2020, 04:51:57 am »
So yeah, you still get an image without the JPAC but just fainter/weaker signal. Your JPAC pics look sharper too, but that may just be because your camera will auto-adjust aperture/exposure settings to available light.

Breadboards can be finicky beasts for video signals. I suggest you simplify your breadboarding slightly by putting the negative (-) ends of the capacitors on the negative (-) rail because then they'll all be connected. Then you can remove those bridging wires and just run a single ground wire from the negative - rail. Ground to video ground rather than main ground (although I bet you'll find they are connected if you test with a multimeter). Then you can take the video output from the rail that runs between your resistor and capacitor + end.

The value of 75 ohm for the resistors works well for video signals, but the 220uF value for the capacitors is mostly educated guesswork. TBH it is all guesswork. So I decided to stop guessing and, rather than hurting my too much head with the math, I found an online low-pass (RC) filter calculator (http://sim.okawa-denshi.jp/en/CRlowkeisan.htm) and plugged some value in. According to that, if we are using 75 ohm resistors and want to filter out frequencies above 60hz (and not below) with this then 33uF capacitors would seem like the way to go. But I guess you've already tried that value.

Good idea to check your VGA cables for resistance end-to-end with your DMM. Occasionally I've found VGA cables that have significant resistance, either by design (eg sometimes happens with VGA cables scavenged from dead monitors) or by poor quality.

Also suggest that you try another computer or at least another video card.

Eventually I'll get around to doing that video amp circuit with the THS7314 chip again. I've still got a few stashed away. Now that I've just had to scrap my international travel plans for next week I might even have some time to do so!

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BumbleChump

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #22 on: April 27, 2020, 08:07:35 pm »
Thanks for the suggestions. I did already try another computer, and GPU. Same thing.

I got the parts to put together a THS7314 RGB amp/low pass filter.

https://www.retrorgb.com/thsamps.html

Did exactly what it said. 75 ohms, 0.1 microfarad ceramic capacitor. I pulled 5 volts and ground from Jamma, and I got this:







It's way worse! I understand that it's gonna be bright, but I was hoping it would at least get rid of the ringing, but the ringing is even more visible now. I did read that someone had a similar issue as me, and got this multi-scart adapter which has a low pass filter in it:

https://lotharek.pl/productdetail.php?id=159

But it's pricey, especially for something that I'm unsure will fix this issue. Is there anything else I can do?



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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #23 on: April 27, 2020, 09:37:40 pm »
Made a discovery!

After reading the manual for the THS7314, I realized that the RGB website failed to mention that an additional 22-100 micro farad capacitor is to be used in parallel with the 0.1 microfarad capacitor.



So I added a 100 micro farad capacitor, as well as three 47k ohm resistors on the input side of the chip, and it completely removed the ringing! (Edit: Actually, I tried it without the additional 100 microfarad capacitor. It looks the same, so I guess it's actually not necessary. Using those three 47k ohm resistors at the input side is what fixed the ringing)





The issue now is that it's still too bright, and if I use higher resistance capacitors the image becomes blurry and colors start to bleed. (I tried three 100k ohm resistors at the input side) But at least now I know that a low pass filter is the solution to my problem. Now to figure out what filter to use, or how to pull down the signal because the THS7314 combined with the JPAC is amplifying the signal too much.
« Last Edit: April 27, 2020, 09:46:32 pm by BumbleChump »

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #24 on: April 28, 2020, 11:59:42 am »
That's good news!

Do you actually need to use the JPAC? You can bypass it with the video, but still use it for the controls if needed.

I once got around this issue completely once (when using PC->JPAC->monitor) by using resistors to ground on the RGB inputs (between the jpac and the monitor) to create a voltage divider (between that resistor and the 75ohm termination on the Sony PVM I was using), reducing the voltage level and therefore brightness. I can't remember what value I used, but probably 75R - 220R.

You could try doing similar, maybe with pots to get a value that suits (200R or 500R pots should be sufficient).
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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver
« Reply #25 on: May 01, 2020, 03:58:13 pm »
I'd like to use the jpac since its shortcut commands are very useful. I also tried it with just the low pass filter, and it looked pretty bad.

But I figured out how to get the picture just right! Whatcha gotta do is put 25k resistance to each of the input lines of RGB, and ~500 ohms on the output lines. I used 545 ohms, but it's a little bit dark. I did a lot of testing with various resistances to find the best picture quality.



The resistance on the input side determines how effective the LPF will be. Too much resistance causes the picture to become soft and blurry, and too little resistance allows the ringing to show through. After testing from 1k ohm to 100k ohm, I found 25k gave the best results. Gets rid of nearly all of the ringing, and the pixels are still pretty sharp.

The resistance on the output side determines the brightness. I used a 470 ohm with a 75 ohm in series, but I think a single 500 ohm would give the best results. I tried to mount the chip to the jpac to reduce the messy vga cable, but apparently the jpac splits off the RGB signals in different directions as soon as the vga pins touch the board, so I wasn't able to do this. I had to build it into the cable. Also need to pull 5v and ground from somewhere. I cut open a usb cable and used that, but I'm sure you can pull it from the jamma pins too.



Now a comparison pic! The upper pic is without the LPF, the lower is with LPF.



The rest of these are with the LPF.













I'm very happy with these results, and I hope this helps anyone else who has the same problem. Thanks again for the help, Zebidee!

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver (SOLVED!)
« Reply #26 on: May 02, 2020, 08:44:40 am »
Wow Bubblechump, well done. Long journey but you got there.

I was surprised that you needed such high values on the resistors, both inputs and outputs, but hey it works so great to know.

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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver (SOLVED!)
« Reply #27 on: February 11, 2023, 12:09:05 pm »
Updating this thread so I'm not spreading misinformation.

For fixing the image, I was on the right path in terms of pulling down the voltage. What I didn't need was the low pass filter though.

Turns out, the Astro's MS8 (and maybe MS9?) monitor doesn't like higher voltage boards. Makes areas of high contrast bleed and ghost.

I was getting the same issue with the mistercade as well. The solution is to add 270 ohm resistors in series to the RGB lines, and a 680-750 ohm resistor in series to the H-sync line. This lowers the voltage on the RGBS lines to levels that the MS8 is ok with. 0.7V RGB and -0.3V Csync in the mistercade's case.

So I made a little adapter that adds those resistors. You can get the parts on ebay easy.



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Re: Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver (SOLVED!)
« Reply #28 on: February 11, 2023, 03:13:47 pm »
Updating this thread so I'm not spreading misinformation.

For fixing the image, I was on the right path in terms of pulling down the voltage. What I didn't need was the low pass filter though.

Turns out, the Astro's MS8 (and maybe MS9?) monitor doesn't like higher voltage boards. Makes areas of high contrast bleed and ghost.


That's awesome, thanks for sharing! I always thought the solution should be a lot simpler.

I've heard (from techs) that those Nanao ms8/ms9 monitors are relatively sensitive to sync levels being constantly changed, like when used in MAME cabs vs a single game PCB. So, it may be worth leaving the monitor off until your OS boots (to avoid the frequency changing while booting) and/or try using ATOM-15 to flash your GPU BIOS for 640x480i.

Quote
I was getting the same issue with the mistercade as well. The solution is to add 270 ohm resistors in series to the RGB lines, and a 680-750 ohm resistor in series to the H-sync line. This lowers the voltage on the RGBS lines to levels that the MS8 is ok with. 0.7V RGB and -0.3V Csync in the mistercade's case.

Very interesting! These are the standard levels for consumer video gear, so no great surprises, though yeah arcade monitors mostly expect the higher levels.

 

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