Results 1 to 9 of 9

Thread: Very faint squiggly line left side of screen

  1. #1
    Join Date
    Aug 2012
    State
    South Australia
    Posts
    28
    Mentioned
    0 Post(s)
    Quoted
    7 Post(s)

    Very faint squiggly line left side of screen

    Hi all

    My apologies if I'm posting this in the wrong section. If someone has a suggestion as to where I should post please let me know, but I thought I would try here first.

    I have a Jomac universal chassis that i purchased 10 months ago and connected it to a 59cm tube I ripped out of a NEC TV. Everything is actually really good with it and haven't had issues with it at all. It was connected to a Simpsons game board and picture quality was excellent.

    Anyway recently I decided to do some playing around and try setting up a MAME system. I threw together a PC, bought a J-Pac and an Arcade VGA. Video is output through the VGA port into J-Pac and in turn video is out through the JAMMA harness into the chassis. Had to adjust picture and colour and once again it looks really good.

    One thing though, I notice a very very faint vertical wavy line that seems to travel up the screen on the left hand side about a fifth of the way in. You can only just see it on a white screen and even then you would be hard pressed to see it, so it's not really a distraction, It only seems to appears when the J-Pac is on. Doesn't occur when a game board is connected.

    I was wondering if anyone knew what that line may be and if it's a cause for concern. Thanks in advance.
    Last edited by sean_skroht; 10th September 2013 at 11:39 PM.

  2. #2
    Join Date
    Jan 2009
    State
    Cairns
    Posts
    13,847
    Mentioned
    456 Post(s)
    Quoted
    3734 Post(s)
    Contact Joey - I'm sure he posted a fix for this somewhere but I can't find it. @Jomac

  3. #3
    Join Date
    Aug 2012
    State
    South Australia
    Posts
    28
    Mentioned
    0 Post(s)
    Quoted
    7 Post(s)

    Actually I want to clarify something I said in my original post.

    Even when the PC and J-Pac are powered off, but the screen is on, the line is still there but straight instead of wavy. Wasn't able to see it before because the screen was black but when i turn brightness all the way up you can see it. As I said, it's about a fifth of the way in from the left. Everything to the left of it is almost imperceptibly darker, and it doesn't bother me as you can't see it when gaming. Just wondered if it was normal behaviour.

  4. #4
    Join Date
    Mar 2006
    State
    Perth WA
    Posts
    1,360
    Mentioned
    212 Post(s)
    Quoted
    118 Post(s)
    This is field ground issue , you need to join the power supply Gnd to the Main earth and also connect the Gnd on the chassis input to the power supply Gnd , this problem is even worse if you connect and earth to the monitor frame or chassis when the Video Gnd and Power Supply Gnd's are not joined .
    Last edited by Jomac; 1st October 2013 at 12:50 AM.

  5. #5
    Join Date
    Aug 2012
    State
    South Australia
    Posts
    28
    Mentioned
    0 Post(s)
    Quoted
    7 Post(s)

    Quote Originally Posted by Jomac View Post
    This is field ground issue , you need to join the power supply Gnd to the Main earth and also connect the Gnd on the chassis input to the power supply Gnd , this problem is even worse if you connect and earth to the monitor frame or chassis when the Video Gnd and Power Supply Gnd's are not joined .
    Do you mean connect this ground wire from the chassis:

    Chassis.jpg

    ....to the 110v side of this transformer?

    Transformer.jpg

    If so, is it ok to join the ground wires at the screw point on the chassis? The ground on the 240v side of transformer is already connected to Main earth. Apologies for the dumb questions, just want to make sure before I proceed.

  6. #6
    Join Date
    Mar 2006
    State
    Perth WA
    Posts
    1,360
    Mentioned
    212 Post(s)
    Quoted
    118 Post(s)
    No mate that Gnd on the chassis is only needed if you are mounting to a metal base plate .

    I mean the Video Gnd , as in Red , Green , Blue , "GND" , Sync , it's easiest to do this at the Jamma harness , The Video Gnd and Power Supply Gnd ( Black 0v ) should always be joined.
    Then at the power supply 5 Volts , 12 Volts and "GND" , This "GND" should be joined to the Mains earth ( Green and Yellow Wire ) .

    Also noticed on your transformer , you have a mains earth for the 240v and 110v connected to screws on either side , they should both be under the same terminal in most situations but you will find that the earth on the 110v goes to nowhere so not important here.

    As general information to all;

    It's very important that in any cabinet where there is mains voltage "ALL" earths should be terminated at the same point , so where the earth comes in from the mains cable there should always be a mounting point , all other earths that go anywhere in the cabinet should come from this point.
    EG: if you are earthing the control panel , power supply and transformer , then there should be one wire from this Earth point to each thing you are earthing
    Never run the earth in a daisy chain , like from the earth point to the power supply and then from the power supply to the control and so on.


    sean_skroht's cab above is an LAI cabinet so is wired 100% correctly as far as safety is concerned , By law they had to be perfect this is why they have a distribution box where the mains power goes in and from this box there is a separate 3 core insulated cable going to each device.

  7. #7
    Join Date
    Aug 2012
    State
    South Australia
    Posts
    28
    Mentioned
    0 Post(s)
    Quoted
    7 Post(s)

    Quote Originally Posted by Jomac View Post
    I mean the Video Gnd , as in Red , Green , Blue , "GND" , Sync , it's easiest to do this at the Jamma harness , The Video Gnd and Power Supply Gnd ( Black 0v ) should always be joined.
    Then at the power supply 5 Volts , 12 Volts and "GND" , This "GND" should be joined to the Mains earth ( Green and Yellow Wire ) .
    Ah yeah of course. Thank you for clarifying.

    I haven't altered the Jamma harness in any way and is shown in the picture. From my research, I believe the video ground "should" be grounded properly through the J-Pac. If I'm incorrect please let me know.
    Here is a picture of the harness:

    Jamma.jpg

    Also I had to replace the Power Supply about a year ago and ensured I had wired it exactly the way it was originally.

    Power Supply.jpg

    I noticed there is an earth wire from FG to GND2 (next to +5v). You mentioned that the power supply's "GND" should be joined to the Mains earth. Is that what this is for and should one also be going to GND. Both GND's go to the Jamma harness but I'm not entirely sure how Video Gnd is connected to GND and to which set in the harness. I assume it is through the J-Pac as I previously mentioned.
    At the moment the power supply is used for supplying power to the credit board and display and the LED's in the player start buttons.

    Quote Originally Posted by Jomac View Post
    Also noticed on your transformer , you have a mains earth for the 240v and 110v connected to screws on either side , they should both be under the same terminal in most situations but you will find that the earth on the 110v goes to nowhere so not important here.
    Yeah that's exactly right. The 110v earth wire goes nowhere.
    Last edited by sean_skroht; 3rd October 2013 at 10:52 AM.

  8. #8
    Join Date
    Mar 2006
    State
    Perth WA
    Posts
    1,360
    Mentioned
    212 Post(s)
    Quoted
    118 Post(s)
    Quote Originally Posted by sean_skroht View Post
    Ah yeah of course. Thank you for clarifying.

    I haven't altered the Jamma harness in any way and is shown in the picture. From my research, I believe the video ground "should" be grounded properly through the J-Pac. If I'm incorrect please let me know.
    Here is a picture of the harness:
    Ok you can see the Video Gnd beside the Video Blue , this was how the first revision of the LAI wired Jamma harnesses were made , the later had the video Gnd on either end of the harness with the other Gnd's , EG: pin 1 & 2 or Pins 27 & 28 , The board it is connected always joins both ends of the harness together so all Gnd therefor joined.
    The reason they moved the Gnd is because quite a few game boards don't join the Video Gnd and Power supply together like they should , I'm not sure about the Jpac but a quick continuity check will tell you the Video Gnd is joined to the other Gnd's , if not either run a link between them or move the Video Gnd to one of the spots at the end of the Jamma harness.

    Quote Originally Posted by sean_skroht
    Also I had to replace the Power Supply about a year ago and ensured I had wired it exactly the way it was originally.
    I noticed there is an earth wire from FG to GND2 (next to +5v). You mentioned that the power supply's "GND" should be joined to the Mains earth. Is that what this is for and should one also be going to GND. Both GND's go to the Jamma harness but I'm not entirely sure how Video Gnd is connected to GND and to which set in the harness. I assume it is through the J-Pac as I previously mentioned.
    That wiring is spot on original configuration , also notice there is even an earth under the mounting screw.
    GND , GND2 are joined internally and yes this is what I meant should be joined to the FG which it is. , good to see you also have the original power supply cover with warning label

    Also just for reference , the reason the FG and GND are joined together was it was deemed necessary to pass the electrical safety standards ., The reasoning was that if the power supply failed internally it could in theory feed the mains voltage directly to the game board then everything connected to it , like controls , coin mechs etc making everything lethal , but when the FG and Gnd are connected any mains fault being AC will pass directly through any component to GND which is of course earthed , this will blow the mains fuse and or trip an RCD. Most importantly using the earth as exit point and not the person touching the machine.

  9. #9
    Join Date
    Aug 2012
    State
    South Australia
    Posts
    28
    Mentioned
    0 Post(s)
    Quoted
    7 Post(s)

    Thanks Joey. That has made a lot of things much clearer now. I'll do what you've suggested and see how I go here.


Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •