Wells Gardner 25K7197 Lines at top of the screen

[skuzzlebutt]

Hello all,

Monitor: Wells Gardner 25k7197 from a NFL Blitz 99 game.

I have been working on my new MAME box for about 2 weeks now and have been learning a ton.  This is the first time I have broken down to ask some questions because I have just run out of trial and error to fix the problem. I have just connected my computer to the monitor with a Jamma Fingerboard and after much work gotten the display to show on the screen.  However, I am only able to get it to work using Soft15 at 15khz and resolution at at 640x480.  Any change to the resolution using QuickRes and I lose the picture.  Even if I hit escape I can tell the resolution changes again, but I can not get the picture back.  So very sensitive.

Even at the picture level I have achieved, there is a significant 'distortion' or lines at the top of the screen.I have attached some pictures of what the lines look like in windows and in donkey kong.  I tested the monitor with the original Blitz board, and the picture is crystal clear.  No lines or problems.  I have tried many different resolutions and 25 or 31 khz, but no other combinations are working for me.  Also, when I shift the vertical stretching, the lines stay at the top of the viewable area.  So they are not fixed at one point of the tube, they are always at the top of the projection of the image.  I am really at a loss here and would like to solve this final (hopefully) hardware problem so I can then focus on the software.

Additionally, I have a problem with the controls on the monitor.  One of the knobs has been removed so I can't adjust the H-Pos.  The picture is heavily shifted left, so I really need to move it to the right.  Is this a common part I could find at home depot or is there an alternative I can use?  Picture is also attached.  if I can't find a solution, I will simply de-solder one of the less used knobs like the blk level and use it for the H-pos.

Thanks for any help anyone can provide. 

[Malenko]

instead of adjusting the VSIZE can you adjust the Vposition?  Despite the breakout board are their any knobs on the back of the chasis?

[skuzzlebutt]

Thank you very much for your reply. 

Yes, I can adjust the v-POS, but that pushes the information I want to see off the screen. The lines still move with the picture.  My video card has adjustments to change the position of the picture, but if I try to bring those settings up then the resolution changes and I lose the picture on the monitor.  I could try to adjust the output from the video card to avoid the problem section on a computer screen and then transfer that to the arcade monitor to see if it fits or avoids the distorted area, but something tells me that will cause problems at some point.  It would be difficult, but if it would work then I can give it a try.

There are other knobs at the end of the picture tube which I have not played with yet.  I will look at/play with them tonight.  I can attach a picture too.  I will draw a line on those knobs so I know where I started just in case.  I don't think there were any other knobs on the circuit board with the WG part number, etc.  But I will look.

Thanks again.

[lilshawn]

on some of those WG chassis, the horizontal knob was on the main chassis board instead of the remote. have a look, it's likely buried in the middle someplace.

[skuzzlebutt]

Thank you for the tip.

Indeed, there is an additional nob on the WG board.  It is is H-Hold knob.  I started to fiddle with the knob and immediately lost the picture. No matter where I turned the knob it would not come back.  This is just like it has been whenever I changed the resolution.  As soon as it was changed I could never get a picture again even returning to the original resolution.  So I rebooted onto a computer monitor, reset the res and 15khz, and rebooted to the arcade.  This time, I adjusted the H-hold very slowly and carefully.  Via a mirror I think there was some very minor changes and improvements to the problem area (top with the lines), but it was hard to tell.  Then I lost the picture again and couldn't get it back no matter where the h-hold was.

Now the bigger problem... I can't get the picture back at all.  Even with rebooting to my computer, moving every knob on the remote or the WG board.  I haven't done much with the knobs on the end of the tube yet.  But all the other knobs I have moved in every way I can imagine and never get close to getting the picture back.  Even bigger problem, this is true on both the PC/Jamma connection AND the original Blitz motherboard.  Just major lines and movement on either with no clear picture.  I am at a loss for a next step.

Thanks again for the tips so far, seems like progress, just need to make a couple steps in the right direction...

UPDATE: Just rebooted after leaving it for an hour.  Still connected to the Blitz board and the picture is crystal clear.  Didn't touch a single knob since it was scrambled and I turned it off.  Guess I'll try the computer connection now...

[skuzzlebutt]

More progress last night.  After I got the picture to appear simply by turning the game on (both blitz and PC), I decided to add a potentiometer to the H-POS which was missing (see picture above).  I have no idea if I chose the right one from Radio Shack, but I decided to give the 10k version a try.  Vioala! It worked and I was able to reposition the screen AND solve the lines at the top of my screen.  So I guess the initial/main problem has been solved.

Now an additonal odd note:  When I changed the resolution, I lose the picture as I did before.  However, now moving the H-POS on the newly added potentiaometer to one extreme of the knob seems to reset the picture.  I still can't change the resolution, but at least now when I try I can return to the old resolution.

I still have some questions moving forward, like what the optimal resolution will be for me and if I have my display set up properly, but at least I am working.  I can now make my control panel and worry about tweaking/optimizing my display and software later.

If anyone has tips for optimizing or explanations of what has been going on with this display, I'd love to hear them.  Either way, thanks for the input provided.

[lilshawn]

right in behind that pot is a 50/60hz pot... try giving that one a little tweak.

often you can get "foldover" at the bottom of the screen due to this adjustment. it makes only sense, that you could get a bit of a foldover on the top if it was out of whack in the other direction a tad.