25" monitor with Jen Shinn chassis from 8liners...

[spun10th]

Hi,

I just got one of these monitors and it has a slight problem.  The picture looks great, but it is slightly "bouncing".  I use this term because I don't know how else to describe it.  The picture/image stays in focus and does not get blurry, however, you can see it slightly moving in a random patern.  It's similar to if you were looking a reflection of the image in a placid water puddle, then the smallest amount of water turbulence made the reflection appear to randomly move (if that makes sense.

I have checked the yoke clamps which appear tight and neck board is firmly seated.  This unit had a two prong a/c power cord already fitted to the chassis and 8liners site says you don't need an iso trans, so that's how I hooked it up (plugged it right into a power strip).  I'm wondering if this is a grounding issues and if I should try to wire it through an iso trans..  Any thoughts?

P.S. I wired this right into working cabinet that has a working g07 monitor in it that does not have this problem.  thanks for the help guys!

[Ken Layton]

Bouncing describes a vertical jumping. Is this what's happening? If so, try adjusting the vertical hold.

[spun10th]

Hi Ken,

I have tried adjusting the vertical hold.  I can move it one way to a point that the image starts rolling, then turn the adjustment the other way until it obviously starts rolling the oppisite direction.  However, the slight movement of the image is present at all points of adjustment between the two extremese mentioned above (rolling one way or the other).  

I verified that the neckboard ground is good (it's going to the black coating on the tube, then to several points on the metal chassis).  

Maybe bouncing isn't the right term.  The image is just kind of slightly shaking in a random pattern (slightly up/down left/right at random).  

[Ken Layton]

Moving left to right would be "weave". Couple that with vertical jump and you have a symptom called "jitter".

Have you verified you have the sync correctly connected for this particular monitor?

Some monitors don't like the sync connections that worked fine for a previous monitor model/brand.

[spun10th]

Ken, jitter describes perfectly what I'm seeing (I'll remember that term now).  The cabinet I rigged this up to for testing is a Jamma cab with a G07 monitor in it. If I recall correctly, the G07 had a jumper wire on the connector plug that tied the vertical and horizontal syncs together.  This plug would not fit on the Jen Shinn chassis (the jen shinn came with it's own proprietary plug).  I wired the jen shinn plug right into the existing jamma harness. Note that the Jen Shinn had only one pin/wire for sync (it has R, G, B, GND, and SYNC). 

Do you have any expirience with the Jen Shinn chassis?  I can't find the schematics for them anywhere.  thanks for all your help.

[spun10th]

UPDATE  I talked to 8liners and they said is sounds like maybe the B+ adjustment is off a bit.  I wil try to adjust that and see if it helps.  The good news, they said if that doesn't fix it, they will send me a new chassis.   So at least I'm not left holding the bag.!

[Grauwulf]

Did they give you a procedure for adjusting it? Just adjusting the B+ at random is not a good thing.

[spun10th]

No, they said just adjust it slightly in either direction and see if it made a difference.  I couldn't find a setting for B+, but here was a pot on the board labeled B limiter which I assume is the same thing.  Regardeless, I tried adjusting this pot slightly (noting it's original position) and this made no difference. 

It should be noted here that I'm using a J-Pac and an ArcadeVGA graphics card.  I noticed with further testing that in addition to the jitter which is apparent while games are loaded (no jitter when the front end software is displayed),  the very first POST screen upon boot has bounce (the next screen showing all hardware addressess is fine), then when the Windows XP spash with the progress bar at the bottom pops up, it also has vertical bounce. 

I can adjust the vertical hold all the way until the picture starts to scroll, then back just to where it stops scrolling and the above two mentioned screens no longer have vertical bounce, however, when I have the vertical hold "tuned" to where these two screens don't bounce, my front end is vertically scrolling when it loads up.  It's like one or the other can be tuned in, not both. 

Should I be sending this chassis back for a replacement?  Thanks guys.

[Lutus]

If no jitter is present while just dipsplaying the front end it sounds like an issue other than B+ for sure and might be a resolution/scan issue? (just guessing)

To sum up:

Jitter present in games

Jitter not present displaying (and navigating?) frontend


A monitor problem seems like it would ALWAYS be jittering no matter what signal the computer was sending.  Just a thought!

[Ken Layton]

I would also think that if the jitter were constant then it would be a monitor problem. Since it's not constant you must have computer resolutions/tweaking problems.

Remember that monitors designed for arcade video applications are expecting certain sync/video level standards/requirements and to be constant.

[spun10th]

Well, I can try messing with some of the resolutions but I have previously ran the tool which automatically sets ini files for all the roms with the right resolutions supported by the arcadeVGA card.  These same ini file settings work fine on my G07 19" so maybe this 8 liners monitor/chassis can't support some of the resoluations? 

I will try tweaking the ini files manually to see if I can get anything to change but thats why I use the arcadeVGA cards now, so I don't have to mess with the pain in the arse resolution tweaking.  What's also wierd is that on my G07 (with the same MAME computer and everything), all boot screens and all games are clear and stable.

In reality, the only thing in the equation changing is the monitor.  I'm thinking either the chassis is bad, out of adjustment, or just not compatible with certain resolutions that most arcade monitors (such as the G07) are capable of.  Any thoughts on this logic, maybe I'm off-base (which is highly likely).  What's also strange and should be noted is that this chassis also does not appear compatible with the act labs light gun VGA box (the G07 was 100% compatible).  With the actlabs VGA box hooked upt (vga box is between computer VGA port and VGA cable going to Jpac), the screen is completely white.  I will do more testig on this issue once I get the jitter issues worked out.  hanks.

[spun10th]

ISSUE RESOLVED>> Ken was right again, this was a sync problem.  There was a jumper switch on the board for V sync ot V+H sync.  Changed to Vsync and the jitter is gone. 

Two other issues with the is montior, seems the degausing cable may not be working 100/% correctly as the screen begins to show some purpling up in the upper right corner if I pause a game (or have the windows desktop on the screen).  The degausing cable does not go all the way up to the corner on that side (it's not perfectly centered to the back of the tube).  Should it be prettey muched centered on the back of the tube and/or taped down to the tube?

The other issue, the actlabs light gun does not work with this unit.  The screen will flash when you pull the trigger but the shot does not register.  It's like you can't calibrate the gun the the screen....