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Neotec NT-500DX Repair

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lilshawn:
 :dunno i just unbolt them and throw my monitors on a cart and wheel them around to service/test them. got an old school AV cart with a plug and cord set on it and everything. makes transporting and testing easy.

i guess don't go poking your fingies in there while it's turned on is a good start.

while the main glass envelope of the monitor is quite thick and strong, (some parts of the front and corners are 1/2" thick) the neck of the monitor is the single most fragile thing on a monitor. (often only 1/16" thick) so if you can get a person on each side while you slide it out of it's old cabinet you lessen the chance of knocking it. most of the time the frame around the monitor sticks out enough to protect it, but sometimes when you go tilting and pushing and pulling on it, you can get it hung up on wires or something in the cabinet and snap the neck right off, and then it's toast. no fixing that.

Rocketeer2001:
So the monitor works, but it has some image issues I can't remedy with the OSD menu.

1. General blurriness. I adjusted the focus on the flyback but I still can't get the image crisp. Seems like if I get one portion of the screen mostly focused, another part gets out of focus. Perhaps the yoke needs shimming?

2. Big Buck Hunter comes with built in test images, one of which is a grid. I could see in the top left corner that the white line looks like it's diverging, but in the top right corner it's fine. Convergence issue perhaps? It also has solid color test screens, and in Red there is a dip in the top left, in the Green there's a slight dip, and Blue there is no dip. The convergence rings on the neck still have a white paint stripe across them indicating it's been factory calibrated, so those obviously haven't been fiddled with. Perhaps it's just time to re-calibrate them, but also sounds like a giant time-suck once you start playing with those rings.

3. There's a white ghosted vertical line that waves around with a frequency of 1 second along the left half of the screen. I tried to film this but it just doesn't show up well. It's visible in person though. I have no idea what could cause this. I did a doodle of about where it is and looks like. Pretend it's flapping about like a wave.

I did notice the degauss coil had come loose at some point in its life and was drooping down on the upper right corner of the screen, so you'd think there would be issues there, but there isn't. Not sure if this relates to any of these issues.

The ghost line is annoying, but is mostly only noticeable on the high score screen. The blurriness is also annoying, but is mostly prominent when trying to read text and the deer don't hold up a lot of signs so...
Not sure if I should start mucking about trying to fix these issues or just be glad I have a working monitor and just play the game.

lilshawn:

--- Quote from: Rocketeer2001 on September 16, 2024, 09:30:41 pm ---So the monitor works, but it has some image issues I can't remedy with the OSD menu.

1. General blurriness. I adjusted the focus on the flyback but I still can't get the image crisp. Seems like if I get one portion of the screen mostly focused, another part gets out of focus. Perhaps the yoke needs shimming?

--- End quote ---

it's an issue with single focus flybacks/tubes. just get the center part as sharp as you can...it's where the action is... believe me, you won't notice it.


--- Quote from: Rocketeer2001 on September 16, 2024, 09:30:41 pm ---2. Big Buck Hunter comes with built in test images, one of which is a grid. I could see in the top left corner that the white line looks like it's diverging, but in the top right corner it's fine. Convergence issue perhaps? It also has solid color test screens, and in Red there is a dip in the top left, in the Green there's a slight dip, and Blue there is no dip. The convergence rings on the neck still have a white paint stripe across them indicating it's been factory calibrated, so those obviously haven't been fiddled with. Perhaps it's just time to re-calibrate them, but also sounds like a giant time-suck once you start playing with those rings.

--- End quote ---

 unless you've done convergence adjustments before... i'd probably leave it. convergence is usually off in the corners. it's really hard to get it good in high deflection angles like these. again, as long as the middle is good... you won't notice it when you are playing a game. you aren't going to have white squares you need to follow around. once your sage brush and trees are displayed... you won't notice.


--- Quote from: Rocketeer2001 on September 16, 2024, 09:30:41 pm ---3. There's a white ghosted vertical line that waves around with a frequency of 1 second along the left half of the screen. I tried to film this but it just doesn't show up well. It's visible in person though. I have no idea what could cause this. I did a doodle of about where it is and looks like. Pretend it's flapping about like a wave.
I did notice the degauss coil had come loose at some point in its life and was drooping down on the upper right corner of the screen, so you'd think there would be issues there, but there isn't. Not sure if this relates to any of these issues.
The ghost line is annoying, but is mostly only noticeable on the high score screen. The blurriness is also annoying, but is mostly prominent when trying to read text and the deer don't hold up a lot of signs so...
Not sure if I should start mucking about trying to fix these issues or just be glad I have a working monitor and just play the game.

--- End quote ---

it could just be your brightness is up too high or your width too wide. the beam can deflect off the side of the tube causing weird ghosting.

you could also try unplugging the degauss coil and see if it goes away. sometimes an old or worn out PTC switch for the coil that is normally supposed to whittle down to nothing will allow excess current to flow causing screen to do some weird things as it stays partially energized.

if it makes no difference... could be noise in the video. try rerouting the cable from the board to the monitor differently. it could be picking up noise from other cables it's being run next to.  also try moving the monitors cables around to different places. i've had issues with the focus/g2 leads being bundled near video cables and causing all sorts of weird video issues. you could also remove the video signal so the no video signal message is displayed and see if there is any evidence of the wave there. it might be super hard to see, but if it is there, there might still be a cap somewhere that is needing replacing causing it.

Rocketeer2001:
I had similar thoughts to issue 1 and 2. I think I've played with convergence rings before, but it's been a while. I do remember watching videos and reading posts about people trying to get a clearer image by messing with those and it was a 50/50 mix of "I got it way better!" and "I think I made it worse".

All good suggestions regarding my ghost line, thanks shawn!
I'll go play around with cable placement and stuff and see what kind of results I can get. You may be onto something about that degauss coil because I believe there's one running down that area.
would those non-polar caps have anything to do with this? They're the only ones I didn't replace.

I'll try to get a better video of it in the event I'm unsuccessful narrowing down the issue.

lilshawn:

--- Quote from: Rocketeer2001 on September 16, 2024, 11:29:42 pm ---
would those non-polar caps have anything to do with this? They're the only ones I didn't replace.

I'll try to get a better video of it in the event I'm unsuccessful narrowing down the issue.

--- End quote ---

it's possible. the bi-polar caps i normally have to deal with are either:

1: on the neckboard for the gun drive. (usually 1uf 200v NP) if you have streaking where if you have a bright spot... and it's good for a bit along the scanline... but further down the scanline it seems to darken or change color. these caps need to be changed out. (again, two 2.2uf in a positive positive config will net you 1.1 uf bi-polar which is close enough)

2: on the main deflection board. (usually 4.7uf sometimes up to 10uf 50v NP (a big fat cap, not a small cap... there seems to be 2 variations and i have no idea what the difference is but this cap is usually a big fat one) this is a cap used for horizontal width timing. so if you have an inability to squeeze down the width because it's too wide, or adjusting the hsize does little or nothing, this is the cap that needs to be changed. (i don't know specifically why there is a difference but i always had piles of the proper large 4.7 non-polar caps. not sure if swapping for the "small" caps would fetch any additional issues.)

see talk about non-polar/bi-polar 10 years ago here: https://forum.arcadecontrols.com/index.php?topic=143822.0 with good ol' ken coming in clutch with the making of bi-polar caps.

"wavy gravy" stuff is usually indicative of power supply. especially down the left side (which is the start of the scanline). What happens is the scanline starts...the cap supplying power, supplies its power, but "runs out of juice" before the scanline can finish, so the scanline gets darker or changes... but then when the scanline ends and goes back to the start again... the cap gets a chance to recharge again. so you end up with brighter image on one side, than the other. sometimes this is static (not moving) sometimes it shows up as a lighter or darker wave in the picture.

not sure if it's just a line you are talking about... or a section of picture that is lighter while the other section is darker.

just lines, i tend to look towards video interference.
whole sections, i tend to look towards power supply.

but i wouldn't discount either.

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