arcade monitor damaged? (pics included)

[Mani]

Hi everyone,

I've been setting up my WG K7xxx 25" arcade monitor with advancemame with some measure of luck. I believe that I'm generally on the right path, but there is some distortion in the top portion of the monitor.

Strange thing is, on some resolutions this distortion is barely noticeable. In other resolutions it is very distracting. For example, when advancemame is configured a certain way, the character in Metal Slug will clearly compress and decompress as they are coming down the screen in their parachutes.

Pictures here: http://www.cs.mcgill.ca/~mghase/monitor

I read that this kind of problem is most probably because of a faulty cap kit. I'm hoping this isn't the case, since (1) this monitor is fairly new and (2) I'm hoping it's just because of video misconfiguration. Hopefully the fact that this problem almost goes away with certain resolutions means that it is not a problem with the monitor.

If anyone thinks this is definately a cap kit problem, let me know so I can have someone repair it. I know it can be done fairly easily, but I have zero experience with electronics and I greatly fear death by electrocution.

Thanks,
-Mani

[OSCAR]

Sorry I don't have an answer, but try posting this at the rec.games.video.arcade.collecting newsgroup if you don't get any help here.

There are some really great monitor techs that frequent that newsgroup and you may get some offers to repair it for you.

[Mani]

Thanks Oscar, I will check out that newsgroup.

-Mani

[MameFan]

If you didn't have it on it's side, I'd say your vertical linearity control is messed up.  But being you have it rotated to 3:4 view instead of 4:3, the CapKit is POSSIBLY the problem.

Good luck

[Mani]

Hi,

It sure does look like I have it mounted vertically from those pics, but actually it is mounted horizontally. The particular pattern being shown for some reason is taking up a small portion of the total width of the screen, although it is centered. I pictured that because it was a good resolution to showcase my monitor's problem.

How do I adjust the linearity control? On the back of the monitor, I have controls for "v. hold", "screen" (I think this is brightness), and "focus". On the front, I have controls for "up/down", "left/right", brightness, contrast, height size, and (I believe) vertical sync. Is it any of these?

Thanks!
-Mani

[Mani]

An update -

I plugged in my MK2 PCB to the Jamma connector to see if the problem occurs with my cabinet's original setup. Well, looks like there is no problem.

Is it possible that my J-Pac is causing this?

-Mani

[krok_le_bo]

A possible cause of your problem is a magnetic interference caused by something in your PC. Try to connect your Jamma connector with your PC started in the location it's meant to be.

You'll see if it's it that causes the problem with a magnetic field...

Hope this can help.

Krok.

[MameFan]

Well then (looking REAL close at the pic I guess I can see you have it mounted horizontally, just cropped the pic).


Yes, this is DEFINITELY a problem with vertical linearity.   Most better analog control monitors and many digital control monitors have a dial/menu option for "V.LIN" to control this.  Basically the idea is to show a cross-hatch pattern, and then adjust the V.LIN so that each square is EXACTLY the same height from top to bottom of the screen.

Here you've got expansion in the first 10% of the screen and compression in around 20-30% of the screen, thus the crooked diagonal line.


If purely caused by magnetism, I'd also notice vertical lines being bent sideways, so it seems to be a signal problem to the yoke itself as part of the vertical drive, not of side interference.

However, if there is a signal generating noise at the precise frequency nearby, it could make it's way into the components and be reflected by the yoke.  (Remember: A yoke is simply windings of copper wires and when electricity is supplied to it, a magnetic field is generated "bending" the electron beam where it needs it.  Clearly the horizontal is working perfectly, but the vertical is the problem)

Being that your game produced a good image but the JPac didn't, it seems the monitor is A-OK, but rather the signal or noise nearby is the culprit.

I know a fair amount about monitors but am far from anything beyond causal tinker-er.  You'll need some input from some good techies.  Post this query to the Sci.Electronics.Repair usenet newsgroup or do some google newsgroup searching for vertical linearity problems with either JPac, arcade monitors, your particular monitor #, etc..

Good luck!

[Mani]

Mamefan and krok_le_bo, thank you so much for your help.

I'm going to try ruling out interference when I get home (i.e. take pc case out of the cabinet and turn off the pc speakers, which includes a subwoofer). I also just received my Trident Blade T64, with that I should rule out a video card problem.

I will also try powering off the MK2 PCB. It is always powered and my J-Pac is hanging right next to it. I hope there's a power plug I can easily remove.

Thanks again guys for being so helpful. I'm getting all emotional now about how great this website is.

-Mani

[Mani]

Well I've ruled out electrical interference from my speakers, the game pcb, and even my PC (placed it well outside the cabinet).

I've also installed a new video card (Trident Blade T64) and the same problem remains.

If it is just a bad vertical linearity setting, then there isn't much I can do about it since there is no vertical linearity control on the monitor.

In conclusion, I'm either going to tolerate it (not likely ), or I'm going to pull out my wallet and pay a technician to take a look at it.

Question: what kind of technician should I hire? General purpose electronics/TV repairman, or an arcade machine technician? Something I should add is that my friend who used to own this particular cab had a problem with its monitor, and he called an arcade technician who replaced the old monitor with this one (an otherwise great quality, bright, clean, no burn-in WG 25") for a mere $300 canadian.

-Mani

[Brunnen-G]

A cap kit will most likely take care of it.  If you have any experience with soldering at all it's a very simple repair.

Otherwise, any TV technician or decent arcade games technician should have no problem repairing the monitor you have there.

If you want to try it on your own, www.therealbobroberts.com should have the kits in stock and also has some great advice.

[Mani]

Thanks Brunnen-G, I'm aware that replacing cap kits is relatively painless. Thing is, my soldering experience is extremely limited, and I wouldn't solder anything more dangerous or more expensive than an AM radio.

-Mani