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Author Topic: Neotec S500 schematic needed - jittery picture only in portions of screen  (Read 546 times)

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pinballvideojuke

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Hi all, I've got a weird video problem, perhaps one of you has seen before or could help with.

I've got an Arcade Legends cabinet with Neotec S500 CRT monitor.

The picture is just fine except when playing vertical games. For instance, Ms. Pac-Man and Galaga have vertical orientation and the scores and upper half of the screen are jittery. UPDATE - I'm not sure what I did, but now the jittery portion is middle to lower part of the screen. The scores are now fine. Ms. Pac-Man isn't really playable it's so bad. Frogger is another that's affected, and a popular game.

This cabinet is original Arcade Legends, but hard drive replaced with Ultracade with 240 games. No dongle. Parallel port turned off. If I'm not mistaken this enables CGA only mode to the monitor.

In display settings (in Ultracade test mode) you can turn ON CGA interlace and adjust anywhere from 1-126? I believe this only for using a VGA monitor, but thought I'd try it. I've tried several numbers from 1 to 30 to 50 to 120 and this setting doesn't seem to help. It only makes the screen jittery during the demo and game select screens. I'm pretty sure it's supposed to be OFF with this monitor (99% sure it's CGA).

Every single electrolytic capacitor has been replaced, about 60 of them. It was quite a job, but the picture is great! I think every horizontal game is perfect, no jitter at all. It's only when playing a vertical game.

Not sure what to try next, but I guess I'm going to try some pots on the main monitor board. There's a couple not labeled, near the sync sections. I can't find the correct manual or schematic for this model monitor.  UPDATE: I have now tweaked every pot and have a good idea of what they all do. I can't make any of them adjust out this problem though. If I mess with x-ray protection R429 or B+ R111 it just shuts down.

Neotec model S500 manufactured Dec. 2005.

Thanks in advance to anyone with any insight.

UPDATE: Everything looks very similar to a NT-2700, so I've taken readings based on the schematic for that model. Voltage readings :
D106 = 117.5 VDC
D107 = 22.28 VDC
D109 = 117.5 VDC
R130 = 11.67 VDC
TP near x-ray pot = 7.72 VDC
No scope available to test FBT#9

If this model is similar to NT-2700 then my B+ is high (should be 100 +/- .5 VDC), D107 is low (should be 26.5), D109 is low (should be 140), and the reading at R130 is actually within spec (12v +/- .5).

I know that adjusting R111 will raise the B+, but how would I adjust the other voltages?

Could these have anything to do with the jittery picture which is only on vertically oriented games?

Anyone have the correct schematics?!!

« Last Edit: September 02, 2018, 09:00:44 pm by pinballvideojuke »

grantspain

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it can't be a monitor fault if the picture is stable on the horizontal games
a video of the issue would be helpful

pinballvideojuke

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it can't be a monitor fault if the picture is stable on the horizontal games
a video of the issue would be helpful

Those pots I spoke of,  I messed with them. In the process I figured out what Neotec this is similar to,  sort of,  and somewhat solved the problem. But I'm not sure what exactly solved it. R111 adjusts the B+, I discovered. Almost as soon as I touched it, the monitor shut down. Seems like it shut down when adjusting one of the others also. Found another Neotec schematic by searching "Neotec R111", which said my B+ should be 100v at D106. The lowest I could go was about 120vdc, so I turned it all the way down. After tweaking the other pots, I seem to have found a more stable image. The jitter that was in the upper part of the screen is more middle,  lower areas and not nearly as noticeable. There is still some jitter, but I think it's acceptable, and I'm out of patience with it.

grantspain

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i doubt that is the correct b+ level, its important to have the correct b+ level as damage can be caused to the chassis
i only ever worked on one neotec in an arctic thunder many years ago so have little experience with these

i would consider contacting neotec directly and asking for a copy of the schematic

pinballvideojuke

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i doubt that is the correct b+ level, its important to have the correct b+ level as damage can be caused to the chassis
i only ever worked on one neotec in an arctic thunder many years ago so have little experience with these

i would consider contacting neotec directly and asking for a copy of the schematic

Neotec contact info?

pinballvideojuke

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Mine is very similar to the 3501 in this post:
http://forum.arcadecontrols.com/index.php?topic=112967.0

It even has those two caps labeled wrong on the bottom of the chassis. My method is to remove one cap at a time and note the orientation, so I didn't have problems, though there was a bit of confusion when I noticed the incorrect markings. Mine does NOT have a separate pincushion board (though I think it could use it), nor does it have a metal shield around the neck board.

It would be nice to know exactly what the B+ should be and what might be needed to bring it to spec. It's turned down all the way, so as of now, my only option is up.

I can't find any contact info for Neotec, even found an article from Bob Roberts, but the S500 isn't mentioned. Mine is clearly marked S500 in more than one place. Bob's article: http://www.thegleek.com/bobroberts/neotec.html

grantspain

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what size tube is this?

pinballvideojuke

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25 incher

grantspain

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dual focus pure flat vga?

pinballvideojuke

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Single focus, not flat - definitely curved CRT. Neotec model number ending in "0" indicates CGA if I'm not mistaken.
CORRECTION - Bob Roberts' post linked above says that flyback is used on VGA monitors. However, in the SAME post it says "I think it's safe to say that if your last two digits in your model number are "00" then you have a CGA monitor... if they are "01" it's an EGA monitor... and "02 & up" would be a VGA monitor.... at least that seems to be the precedence."

This is the flyback:
http://www.arcadeshop.com/i/291/neotec-25-27-vga-flyback.htm
MRCFT - 252

« Last Edit: August 31, 2018, 02:01:00 pm by pinballvideojuke »

grantspain

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tough call without schems, b+ level is critical


pinballvideojuke

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Re: Neotec S500 schematic needed - jittery picture only in portions of screen
« Reply #11 on: September 02, 2018, 09:12:23 pm »
tough call without schems, b+ level is critical



I agree 100%, and I don't know where it's supposed to be. I do know B+ is all the way down now and that's one thing I've changed. It was slightly higher. I'm curious if I turn it back up if the jitter will go back up higher on the screen, but not knowing what it's supposed to be, I'm scared to mess with it. If it's supposed to be 100, it's already too high. Need the correct schematic!

I've updated the original post to include voltage readings and other information.

How do I adjust this x-ray r429 pot? I messed with it a little and too low it won't start up, too high it shuts down, so it's really about in the only area it can be anyway. I wish I hadn't turned it, but I was trying everything to get this jitter out.

I'm going to try Chicago Gaming Tuesday when they're hopefully open, but I'm not liking my chances of getting help on this monitor from them, since they didn't make it.

Appreciate the help.

grantspain

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Re: Neotec S500 schematic needed - jittery picture only in portions of screen
« Reply #12 on: September 03, 2018, 02:01:40 am »
blimey you are having a fiddle about, shame they did not glue that x-ray pot- try setting to middle and coming down anti clockwise until monitor stays on


grantspain

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Re: Neotec S500 schematic needed - jittery picture only in portions of screen
« Reply #13 on: September 03, 2018, 02:37:29 am »
btw you may be looking at this fault completely wrong, this could be a vertical deflection circuit issue or even something to do with the vertical frequency
do you have a video of the issue

pinballvideojuke

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Re: Neotec S500 schematic needed - jittery picture only in portions of screen
« Reply #14 on: September 03, 2018, 07:33:32 pm »
blimey you are having a fiddle about, shame they did not glue that x-ray pot- try setting to middle and coming down anti clockwise until monitor stays on
Thanks mate! I haven't a problem with the monitor staying on, once I found a middle position for the x-ray pot and turned the B+ R111 all the way down. I suspect I could turn it back up a bit, if I thought it would help anything, but I don't know what voltage it's bloody supposed to be!

pinballvideojuke

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Re: Neotec S500 schematic needed - jittery picture only in portions of screen
« Reply #15 on: September 03, 2018, 11:32:35 pm »
btw you may be looking at this fault completely wrong, this could be a vertical deflection circuit issue or even something to do with the vertical frequency
do you have a video of the issue
I really tried to video the issue, but it doesn't show in the recording. I turned off the stabilizer setting in the camera, but it still comes out looking better than what I'm actually seeing. I've fiddled with it enough, I'm leaving it. The worst is Ms. Pac-Man, which sucks since it's so popular, but it's probably more annoying to me than anybody else. Most all the other games look great, nearly perfect. Even other vertical games, like Mr. Do. It's perfect. I don't get it.

Anyway, I'm still curious where the right schematics are for this model and what these voltages are supposed to be and how to adjust them. For another day, I guess. Thanks a million for all your help.

lilshawn

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Re: Neotec S500 schematic needed - jittery picture only in portions of screen
« Reply #16 on: September 05, 2018, 10:08:22 pm »
side note... DO NOT go to the neotec website... it's been expired and taken over and now serves up malware ads.

pinballvideojuke

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Re: Neotec S500 schematic needed - jittery picture only in portions of screen
« Reply #17 on: September 05, 2018, 10:11:45 pm »
side note... DO NOT go to the neotec website... it's been expired and taken over and now serves up malware ads.

Thank you! 

infinitronics

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Re: Neotec S500 schematic needed - jittery picture only in portions of screen
« Reply #18 on: October 20, 2018, 03:47:13 pm »
I have the the same machine, and had the same issue.

The top portion of the vertical games like Ms. Pac-Man were jittery to the point of looking out of focus.

I was able to fix it by adjusting the Horizontal Hold and Horizontal Phase on the monitor chassis.

My machine also had an issue where the vertical games would not always show up in the middle of the screen, but to the left, mostly. 

The aforementioned adjustments fixed that problem as well.

  
 

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