Author Topic: Scrolling dark line on my Neo Geo monitor--Update! (Read 2033 times)

2PacMan · « **on:** June 28, 2006, 11:33:59 am »

Help guys. Kind of hard to explain this, but basically there is a darker (not black) line that scrolls from the bottom to the top of the screen continuously. It starts the minute the game comes up and never stops. It looks like it might be caused by some sort of interference. Any ideas? It wasn't doing this a few days ago, but I moved the machine and a 2 x 2 (inches) piece of metal fell out of the game. It was just a metal plate, but I don't know if the guy who had it before me was using the plate to sheild something or what. Or maybe it was just a useless piece that was stuck somewhere. I'm not sure what type of monitor it is (it says Zeneith on the back). It's out of a converted Neo Geo. Here's a pic...kind of hard to capture this on a picture, but this is the best i could do.

grantspain · « **Reply #1 on:** June 28, 2006, 12:30:28 pm »

looks like some sort of earth issue or the usual cap kit thing

2PacMan · « **Reply #2 on:** June 28, 2006, 12:41:42 pm »

When you say 'earth issue', are you referring to the grounding?

Silver · « **Reply #3 on:** June 28, 2006, 01:35:56 pm »

lines that scroll up/down a monitor - assuming its not that fast - are often mains interference (The AC frequency of mains is similar to the vertical refresh of tv's/arcade monitors.).

I would suggest the metal plate that fell out was shielding the video signal from the power supply/power cables.

Turn it off and look where the cables run of see if there is a place for mounting the metal plate near the mains transformer. As it's metal, be VERY careful where you place it. Don't move the plate while its plugged in.

grantspain · « **Reply #4 on:** June 28, 2006, 05:55:17 pm »

Yes i was refering to grounding,strange though the metal plate.some monitors do require shielding for scan coils and signal-need to know the monitor type though before going further

2PacMan · « **Reply #5 on:** June 29, 2006, 08:27:11 am »

I did a little more work on the game last night. The on/off switch behind the game no longer works, but there is still some wiring going through it. When i switch it on/off, the lines on the screen get worse. I tried unhooking it, and it actually made the screen worse, so I kept the wires plugged in. I'm almost totally convinced it's an interference issue.

Silver--it is a slow scrolling line. I'm with you, I think that metal plate did sheild a signal from somewhere, but i can't figure out where it goes. Any suggestions? It was up in the monitor area after it fell out, so it was up in that area at one point. Actually, i take that back. I did lay the machine on it's back to unload it from my truck, so I guess it's possible it came from the bottom area and just worked it's way up in the monitor area. I think it was just 'set' in there somewhere for a quick fix, i don't think it was every screwed in, or a permanant part of the original monitor/game.

I looked last night, and to me it looks like a WG K4600 monitor with an RCA picture tube. I looked at Bob Roberts monitor site, and that looks like what mine is. It's got the two vertical boards in there. And my friend took my digital camera on his vacation, so I can't take any more pics until next Wednesday

Is there a general area of a monitor that needs to be sheilded, or is it just sort of a random trial and error thing?

Kevin Mullins · « **Reply #6 on:** June 29, 2006, 10:45:07 am »

If it is a WG4600..... I would re-seat the daughter cards, just typical practice after moving one.
Since you layed it on it's back, do you think the metal plate may have come from up in the marquee / speaker area?

What do you turn the machine on and off with if the switch is broken?
I would redo that wiring and make sure it's actually going through an EMI filter also.
(should be one of some sorts in the machine)

It does have a three wire power cord right?
Make certain the ground is connected through that filter or something similar depending on what you actually have in that cabinet.
Sometmes there is a "coil" directly wired to the power switch, that is also an emi filter.
Maybe that is why messing with the switch effects the screen also.

2PacMan · « **Reply #7 on:** June 29, 2006, 10:58:18 am »

Hmm, that's possible, the metal plate could have come from the upper marquee/speaker area.

The thing is, when i bought the game from the guy, we tested it and it was fine, then i drove home, hooked it up at my house, and i get the lines. So to me, it seems like i knocked something loose or something got screwed up on the way home. That's why i'm thinking it's probably not a wiring issue. I just plug/unplug the game to turn it off an on. I guess i could try reseating the daughtercards tonight, do you really think that's what the problem is? Could the speaker above the monitor somehow be causing the interference? The only thing i've known speakers to do is discolor a monitor, but the color on my monitor is fine. Maybe i should try to see if the metal plate should be sheilding the speaker?

grantspain · « **Reply #8 on:** June 29, 2006, 01:34:58 pm »

i know this might sound pretty strange but a flo tube in your top box can cause very strange interference faults on your monitor,why not try disconnecting the power to the marquee light but whatever you have a mains interference problem

Kevin Mullins · « **Reply #9 on:** June 29, 2006, 01:55:31 pm »

I totally agree...... a 120V (US) line interference.

Might be a flourescent ballast causing it.
(not knowing what is in the cab)

2PacMan · « **Reply #10 on:** June 30, 2006, 08:22:23 am »

Thanks for the advice guys. Last night I removed the entire florescent light fixture as well as the two speakers located above the monitor, and it still has the rolling line. So i have eliminated the speakers/ballast/flo tube as the problem for the interference. I did reseat the two monitor daughter cards. I also set a big piece of sheet metal on top of the transformer at the bottom of the cabinet....that made no difference either. What part of the monitor do you think is picking up the interference? Maybe i should try to sheild the part recieving the interference instead of trying to sheild the source? You don't suppose anything in my house could be causing the interference, do you? I'm half tempted to wheel it outside and plug it in and see if i still get the lines. I have several other arcade games inside my home, and none of them get any kind of interference.

Kevin Mullins · « **Reply #11 on:** June 30, 2006, 10:31:21 am »

I have seen a machine pickup interference from another machine that was next to it. Only happened when the other one was on.
Does yours do it when everything is shut-down around it?

I would still check that the power cord is running through an emi filter.
(since the switch is bypassed)
Actually I would compare the power wiring to another machine and fix the switch.
Just eliminate the possibly of it being something coming through the wall outlet.
(which is what the emi filter does)

If you unplug the machine from the wall, does it still do it?
(just kidding...

.... ignore that)

2PacMan · « **Reply #12 on:** June 30, 2006, 10:59:15 am »

There is definately something screwy about the wiring. There are two tranformers at the bottom of the cabinet, and both seem to have wires plugged into them. There are also a few wires coming from the bottom of the cab, as well as one from the Neo Geo board that go no where and are just cut off. I'm a novice when it comes to wiring, so i might need your guys's help. As soon as i get my camera back (next Wed.) i'll take some pics and maybe you guys can help me out.....there are no other machines turned on sitting by it.....no machines by it at all right now actually.

But it still doesn't explain why it worked at the other guy's house, but not at mine. There must be some sort of quick fix for this he did, or something got knocked loose on the monitor during transport.

Nipedley · « **Reply #13 on:** July 01, 2006, 02:39:32 pm »

Probably a silly question but did you try asking the guy about it? If he had the same problem he can most likely help you out a lot better than us.

2PacMan · « **Reply #14 on:** July 01, 2006, 09:47:36 pm »

I've emailed him with no response so far. But with the holiday weekend, i wouldn't be surprised if he's out of town for the weekend. Hopefully he can shed some light on this. Any more suggestions would be greatly appreciated.

grantspain · « **Reply #15 on:** July 02, 2006, 02:18:19 pm »

always the most obscure faults turn out to be something really stupid.
the most important thing to do first is eliminate the areas of the machine which are working correct.
first try disconnecting your rgb signal from the monitor,turn up the brightness to see if the interference is still there,if its still there then its most likely to be the monitor or power input,if not then its something to do with the power supply or the game board.
if you still have it with signal disconnected then check your mains input goes through a filter then an isolation transformer then to the monitor,also check all the earth wires are linked correctly back to the transformer.does you cabinet run the psu from the same wire as the monitor?
some psu require the common and earth to be linked otherwise you can get interference
would be better to get a picture of your wiring though

2PacMan · « **Reply #16 on:** July 02, 2006, 10:20:38 pm »

Good idea Greatspain...i'll try to unhook some of the wires to the monitor and see what happens. I won't damage the monitor by unhooking some of the wires, will I? I pulled the entire connector away from the neo geo PCB and just got a white screen with no scrolling line. But i'm not sure if the white screen just masked it, or if it was really gone. Then i tried to pull the cartridge out of the pcb and i get the scrolling. So i've eliminated the cartridge as being the problem. Also, i think i found where the metal piece came from and I don't think it had anything to do with the monitor, it looked like it was used to hold a cp on at one time. I'll have some wiring pics late this week, so you guys can see what's going on. Thank you so much for your advice so far.

grantspain · « **Reply #17 on:** July 03, 2006, 05:23:09 am »

its a shame you don't have another jamma board because that would prove whether its a game board fault or not

2PacMan · « **Reply #18 on:** July 03, 2006, 08:20:42 am »

I have a capcom bowling. Is that a jamma board? I thought neo geo boards were slightly different than jamma. If i could use it just to get the screen to come up, even if it's unplayable, that would help.

grantspain · « **Reply #19 on:** July 03, 2006, 11:10:41 am »

every neo geo i have worked on(whether one , four or six slot) are jamma,mind you knowing you americans you would be have to be different.i'm sure if its 28 pin then its the same(its only the voltages to be careful about anyway),i think the only difference is the d button anyway

Kevin Mullins · « **Reply #20 on:** July 03, 2006, 12:56:30 pm »

Yes . . . both of those are JAMMA.
The controls will be a little wanky, but you should pull up a picture well enough to tell if the interference problem is still there.

2PacMan · « **Reply #21 on:** July 07, 2006, 10:29:33 am »

Hey guys, just an update since i haven't posted here in a few days. I did get a hold of the guy that sold it to me and he offered to come over and see if he could fix it. He's a really nice guy and wants to make good on our deal, so this could turn out great. But because of this, I am holding off on tinkering with this anymore because i don't want to inadvertantly create any more damage until he gets a chance to look at it, which won't be until next Saturday. I'll let you guys know how it turns out. I'm pretty optimistic though

2PacMan · « **Reply #22 on:** July 17, 2006, 10:13:27 am »

OK, just an update for anyone following this thread. The guy came over and fixed it for me. It was mains interference. Basically he just cut a ground wire that was going to the transformer and that did the trick. He said it was a bad ground coming from the PCB. Why it wasn't having interference at his place, but doing so at mine, i don't know. In any event, I'm very happy it's fixed, and I was glad i bought the game from a great guy that fixed it for me instead of just saying 'too bad'.

My cabinet was a conversion, so there are alot of wires in there that connect to 'nothing'. I was asking him about one of these wires up near the monitor. He said it was the montior ground. So i said "oh, so the monitor's not grounded then?" He said 'well, not technically, but you don't have anything to worry about, it's not going to shock you or anything." The game is playing fine now and everything appears normal. Should i have anything to worry about?

Kevin Mullins · « **Reply #23 on:** July 17, 2006, 02:07:18 pm »

Well..... if he cut what I think he cut, then it means the entire cabinet is not grounded.
Will it function fine? Sure.
Is it safe? Not entirely.

If that cab has an emi filter and all that in it then you should be able to hook all the grounds back up just fine. I'm assuming it does not have an emi filter because of the problem you had and the fact that the interference is coming from the mains.

Does the power cord run straight into a large transformer of some sort without going through anything else?

2PacMan · « **Reply #24 on:** July 17, 2006, 02:25:48 pm »

There's a switching power supply in it. So it looks like the main line goes into a transformer, then the transformer wires go to the switching power supply's main screw terminals and then is wired from that on out. It looks like the second transformer powers the monitor. Like i said, for some reason there are two transformers in it. He said i could take out the first one and just have the main line run right to the power supply, but he said it wasn't a necessity and i just assume leave well enough alone if it's working fine now.

Kevin Mullins · « **Reply #25 on:** July 17, 2006, 05:53:56 pm »

Bob Roberts has an excellent layout on his web site for a basic cab setup.
His shows it as a Pac cab layout, but the only difference is what you would hook up to the switching power supply. (+5 +12 -5) It has a different connector on the end is all.
Set the switching power supply outputs just like you have them now.
The key is everything else. The mains, the transformer, fuse block and emi filter.
And take special note as to what is dead in the middle of his setup...... an EMI filter.

I think with a little re-wiring and cleaning up of all the loose ends you'll be good to go for a long time.

Anyways, check it out : http://homearcade.org/BBBB/acwiring.html#earth


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