Author Topic: horizontal band problem (Read 8058 times)

clutch · « **on:** March 06, 2011, 02:59:19 pm »

After a while, my Nanao 2933 multisync will get this 'band' of dots that appear to be leaning to one side. This band will slowly travel from top to bottom and repeat over and over slowly. Any idea how to fix this or what the issue is?

Jack Burton · « **Reply #1 on:** March 06, 2011, 03:48:11 pm »

Kind of sounds like interference in the video signal. Are there any power lines or other electrical devices near it?

clutch · « **Reply #2 on:** March 06, 2011, 04:55:49 pm »

I thought so too.

Some more info: I have my computer motherboard, psu, dvd drive, and JPAC mounted to a board and slid into my Blast City Cabinet.

I pulled everything out and connected stuff one cable at a time to try and identify the source of interference. That is, I had the board outside the cabinet and hooked everything up. I did not see the band.

Slid everything back in and I was good until about maybe 30 minutes into it. The band reappeared!

Interesting thing is, I can move my wireless mouse and the band's 'dots' change configuration. They kind of slow down and change direction within the big band.

clutch · « **Reply #3 on:** March 06, 2011, 05:00:01 pm »

Just turned off cabinet (because of the security switch in the door) and unplugged the wireless mouse. The band is still there

Jack Burton · « **Reply #4 on:** March 06, 2011, 05:34:39 pm »

How long did you leave the stuff hooked up outside the cab? If it was more than an hour with no band then you can safely say it's not the monitor itself.

Are you sure that the wireless mouse is changing it? Even it it's not the source, it could still be affecting whatever actually is interfering with your video signal.

A band of interference that travels from top to bottom is usually a ground loop:

http://en.wikipedia.org/wiki/Ground_loop_%28electricity%29

So you need to make sure that that you don't have your cab and your computer plugged into two different outlets. It could even be that two other devices in your house could be like that.

clutch · « **Reply #5 on:** March 06, 2011, 10:34:27 pm »

Thanks for your help. I have tried isolating things. Computer and cabinet are plugged into same power strip. Made sure nothing else in house was being turned on or off. Things will be fine for a minute or two and then bam! I've taken the computer out of the cabinet and disconnected the JPAC and it is still there. Here is a video of the problem.

clutch · « **Reply #6 on:** March 06, 2011, 11:21:57 pm »

Figured it out. It is the crap JAMMA 001 harness. I plugged the regular one in and the interference disappeared. Now to figure out what is wrong with the harness.

clutch · « **Reply #7 on:** March 07, 2011, 11:24:51 pm »

Back to square one. Plugged in what I thought was the 'good' harness. Got the same problem. I am seriously bummed out by this. It would be different if the band appeared immediately, but it is random.

clutch · « **Reply #8 on:** March 08, 2011, 12:18:10 am »

A little progress. Decided to take the vga cable out of the picture and plug the computer's video out through the JPAC with a jumper installed on 31khz. No band but you can tell the picture is off. It is muddy and the images have a slight shadow next to them.

clutch · « **Reply #9 on:** March 08, 2011, 01:33:07 am »

Does anyone care for these updates? I feel like I am talking to myself.

Anyway, I think the problem lies with the 15 pin monitor connector that hangs down from the chassis. I disconnected that and the interference went away on the jamma game.

That is fine, but now I don't know what to do about mame-ing. I prefer the cable over running the video through the JPAC for obvious reasons, but how do I eliminate the noise?

I'm thinking about buying an arcadeVGA card, but really don't want to waste the money if it doesn't help anything.

Jack Burton · « **Reply #10 on:** March 08, 2011, 05:05:13 am »

I'll try to read your posts closely and offer some suggestions tomorrow. Right now I'm goin' to bed.

gryhnd · « **Reply #11 on:** March 08, 2011, 06:55:10 am »

Just saw this. My first thought, and then I see you found the same, is the VGA cable.

You might try a beefier VGA cable. I had a thinner "inexpensive" one once that picked up weird interference (or generated it itself).

Two other thoughts if a better cable does not help, are to try and route the VGA cable differently (try not to have it run in parallel with any other wires, for example) and/or put some ferrites on it.

...says the non monitor expert.

clutch · « **Reply #12 on:** March 08, 2011, 10:22:05 am »

Thanks guys. The cable that came with it is the beef-iest cable I've seen. It is also one of those that has the 9 pin missing. I'm scared to death to use a regular cable with the 9 pin intact. Not a lot to re-route because it is basically a big box with a monitor in it. The cable just kinda hangs there. I'll take some pics later.

clutch · « **Reply #13 on:** March 08, 2011, 12:32:31 pm »

Tried another VGA cable. Got exact same result. Now that I'm swapping between going through the JPAC for video and the vga cable, I have noticed that the colors are really muted and dull going through the vga connector. So it has something to do with the chassis or the connector on the chassis?

Here are a couple of pics. As you can see, I'm not hurting for space in there:

Here's where the vga cable goes:

clutch · « **Reply #14 on:** March 10, 2011, 08:17:29 pm »

In the beating a dead horse dept:

Two ferrite chokes on the vga cable didn't help a thing. I tried to show the difference between the jamma video vs the vga video:

Through vga cable. Sharper graphics, but muted colors and that $$#%#Q@ scrolling band of #$$##:

Through jamma connector. More vivid colors, but muddy graphics:

clutch · « **Reply #15 on:** March 15, 2011, 11:22:16 am »

Help me Obi-Wan, you're my only hope.

gryhnd · « **Reply #16 on:** March 15, 2011, 11:37:02 am »

Quote from: clutch on March 15, 2011, 11:22:16 am

Help me Obi-Wan, you're my only hope.

I got nothing. Out of my knowledge zone.

clutch · « **Reply #17 on:** March 15, 2011, 02:02:34 pm »

No problem. Thanks for the suggestions.

So far, I've tried two ferrite chokes up next to the connector with aluminum foil wrapped around the cable, a 50 dollar power strip with 'line filtering', and wiring a new plug to ground the cabinet (just for snicks).

No change. Last thing I'm gonna try to remove the d-sub connector from the chassis and hold it away from the power lines. If that doesn't work, then I'll just have to get used to it.

Luckily, I have the jamma connector to fall back on, just can't auto switch between 15 & 31. Have to jumper each time.

clutch · « **Reply #18 on:** March 15, 2011, 05:18:54 pm »

Finally a glimmer of light.

Took off the d-sub connector, looped the cable up over the monitor frame so that the wires are 'free-floating'. I still got the band of noise. I then unplugged the connector that connects the jamma harness to the chassis. Bam! Monitor looks perfect. It isn't dark and dull any more either. The color pops! I had to keep looking underneath to make sure I wasn't running vid through the JPAC. I'm still cautious, but this is definitely a step in the right direction.

lilshawn · « **Reply #19 on:** March 15, 2011, 05:59:15 pm »

that tag of wires from the board to the chassis frame must have been acting like a little antenna and picking up a stray interference signal from somewhere.

gryhnd · « **Reply #20 on:** March 15, 2011, 08:14:46 pm »

Quote from: lilshawn on March 15, 2011, 05:59:15 pm

that tag of wires from the board to the chassis frame must have been acting like a little antenna and picking up a stray interference signal from somewhere.

or perhaps the equivalent of a ground loop?

lilshawn · « **Reply #21 on:** March 15, 2011, 10:22:05 pm »

If it was still hooked up to the jamma harness then maybe. But I would assume you disconnect it to hook up the DB15.

Jack Burton · « **Reply #22 on:** March 16, 2011, 01:04:00 am »

sounds to me like increased resistance in the video signal.

I have a psx>rgb adapter from ultimarc and it adds noise and darkens the colors of the image.

Same goes for when you split the video between two sources. A backfeed(?) loop can form here.

For instance I have a monitor with RGBHV IN and OUT on it. If I even have a cable plugged into the OUT input it adds resistance to the signal and darkens the image. If I plug that cable into a monitor it gets even darker, and if I turn the other montitor on it starts to look like crap until I boost the voltage of the signal with the Ohm level switch in the back.

I believe you were getting a little bit of increased resistance from that cable you unplugged.

clutch · « **Reply #23 on:** March 16, 2011, 08:26:47 am »

Interesting. Ideally, I shouldn't have to unhook anything from the chassis, but with equipment this old who knows. This has definitely been a learning experience for me.

boardjunkie · « **Reply #24 on:** March 19, 2011, 12:28:20 pm »

The "hum bar" indicates a grounding issue. I assume this has a switching power supply. Try disconnecting the "FG" wire (at the AC cord input) and see if that quiets the video.

clutch · « **Reply #25 on:** March 19, 2011, 01:51:54 pm »

Pardon my ignorance, but which wire is the FG wire? The one connected to the hole the third prong on the plug goes into?

boardjunkie · « **Reply #26 on:** March 21, 2011, 09:56:13 am »

I responded too quickly. This is a MAME machine, not a dedicated arcade machine. Is the monitor frame grounded? There should be a wire bolted to the metal frame of the monitor that ties to a gnd bus somewhere. If there is no gnd wire there, run one from the monitor frame to the case of the power supply of the PC (one of the pwr supply mounting screws) and see if that clears it up. Grounding can be fussy and cause a bunch of strange issues if not done right. The old vector arcade games were incredibly picky about grounding.....to the point where the monitors could be damaged by improper grounding....

clutch · « **Reply #27 on:** March 21, 2011, 10:24:23 am »

Thanks BJ. I should have stated from the start what cabinet I have. It is a stock Blast City cab wired for jamma. No mods by me other than hooking up my pc through a J-Pac. I'm just curious if I did fix the noise issue, would that fix the darkness issue that comes from having both connectors connected to the chassis as well? At this point, I'm about ready to just go with my ghetto fix.

boardjunkie · « **Reply #28 on:** March 21, 2011, 10:43:58 am »

Both connectors.....you have 2 sets of video cables connected to the monitor at once? if so, thats bad mojo. That may be your only problem. The darkness would be due to that, and the noise issue as well. Only use 1 video input to the monitor at a time.

clutch · « **Reply #29 on:** March 21, 2011, 11:18:08 am »

Yeah, the video in's are connected, but only one is in use at a time which I'm guessing under normal conditions shouldn't present any problems.

boardjunkie · « **Reply #30 on:** March 21, 2011, 11:38:24 am »

Its really not good to do this. The other video cable thats still connected even tho the board/pc is not on will load down the one in use. I dunno if any damage can be done, but either way its not a good idea.

Humor me, disconnect the second video input from the monitor and just connect one signal cable to the monitor directly. Tell me what happens....

clutch · « **Reply #31 on:** March 22, 2011, 12:36:19 am »

That's what I did above and the problem stopped.

However, the chassis comes with both inputs plugged into the board. What I did to fix the problem is not typical. Everyone else who owns this particular model would be having the same issue if both plugs being connected at the same time was the source of the interference. I think my issue lies elsewhere and unplugging one cable just happened to fix the problem.

boardjunkie · « **Reply #32 on:** March 22, 2011, 11:56:52 am »

Can you post a link to the manual for that monitor? I think 2933 is incorrect as far as model # goes. I bet it says in the manual to connect only 1 input at a time.

Anyway, just because there is 2 inputs doesn't mean they should be connected at the same time. At the very least thats asking for a gnd loop. That would be like connecting the BNC and HD15 inputs at the same time on a computer monitor set up with those inputs. So.....just because its physically possible don't mean the monitors gonna be ok with it.

So....you need a mechanical switching device to isolate the 2 inputs and switch between them. A cheap monitor switchbox would make a decent enclosure to have something built in. I would think some multisection rotory switches and the proper connectors would get you to where you need to be.

clutch · « **Reply #33 on:** March 22, 2011, 01:47:31 pm »

Closest I have online is a 2931 manual:
http://hem.bredband.net/emergencycallambulance/Monitors/MS-2931/MS-2931_Service-manual_full.pdf

Here are the labels on the back of my monitor:

boardjunkie · « **Reply #34 on:** March 22, 2011, 06:47:45 pm »

Note....you don't have to remove the connector from the board. Just remove the unused (at the time) video input connector (either the HD15 or the molex) at the side of the chassis. The monitor doesn't have any kind of active input signal sensing/switching, so its up to you to find a way to switch between the 2 video sources.


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