Wells Gardner 25k7193 Red bleed through and low brightness

[noahstauff]

Hi,

I'm currently in the process of converting my Jamma Street Fighter II to mame. I got it all hooked up via a J-pac but the picture is just too dark. I can barely see my layouts and unless it’s a very light color game it is difficult to see. I can turn the brightness up on the monitor but it did not help all that much, then I remembered that the flyback has a brightness control on it too. I turned this up, but instead of just making the screen brighter it added red to anything that’s black. When I turn it up all the way so the picture disappears the screen shows solid pink with diagonal pinkish red lines running through it. Is this normal? I thought that it should show solid white? I was thinking of ordering a cap kit, but wanted to post on here first.

Thanks in advance,
Noah

[HaRuMaN]

How did it look with the Street Fighter II?

If it looked ok, you may need some sort of video amp.  I am not very familiar with a J-pac, so hopefully someone with some experience will chime in.

[MonMotha]

The JPAC has a video amp, so you should be good in that department.

Counterintuitively, the "brightness" control doesn't actually control brightness.  What it actually controls is the level at which the monitor gets "black".  If you have it set too long, things that should be dark but still visible are completely black.  If you have it too high, things that should be totally black look gray.

The screen (G2) control behaves similarly but is a lot more coarse.

If your display is dim, what you actually want to adjust is CONTRAST.  That should make things get brighter while keeping what is supposed to be black actually black.

There's a degree of interaction between the controls, so you may have to futz with them both.

If there's still too much red you'll need to adjust cut-off/gain, usually on the neck board.  If there's too much red on dark spots, turn down the cut off.  If "bright red" is too bright (brighter than the other two primaries), turn down gain.  Cut-off is sometimes called bias, and gain is sometimes called drive.

But yes, an important first question was how it looked on the original SFII hardware?  If it looked good, go ahead and do the adjustments described.  If it looked bad too, you may have a fault that isn't simply adjustment related.

[noahstauff]

Sorry for being silent for so long, but my mother was having surgery so the family was in Minnesota for the past week. I installed a cap kit into the monitor, and it didn't do anything but allow the picture to fill the screen. I also noticed that someone had done some rework in the past it was some wire connecting to a cap lead with another capacitor in line going to some metal thing near the flyback transformer. There was another rework wire but I cannot remember what it was doing. I think that the guy I bought it from may have done this, and he has not turned out to be very reputable. Should I remove the rework? I also was hopeing that the cap kit would fix the problem of a strange band at the bottom of the screen that only appears when in 640x288, but of course it didn't. I've taken some pictures and will attach them to this post.
I would like some more tips so hopefully I will get to play my mame setup at last.

Thanks for all the help,
Noah

p.s. if the images look streched its because I had to resize them

The 1st picture is the brightness turned all the way up

The 2nd is when I turn down the flyback brightness to where there is no red

The 3rd is a strange pink bar that only apears when in 640x288 resolution

*Edit* I removed the bar at the bottom in picture 2 by adjusting the 50-60hz pot of the chassis *See picture 3*

[noahstauff]

Anyone?

[MonMotha]

To properly adjust this, you'll want a color bar ramp pattern.  The pattern should have have red, green, blue, and white bars ranging from totally black all the way up to full intensity.

First set your brightness control (on the remote or user adjustment area of the chassis) to minimum and contrast to about mid-scale.  Adjust the screen control (on the flyback) so that the picture is just barely visible or at the threshold of being invisible.  Now turn up brightness until the bottom 10-15% of the white/gray ramp is fully black and the rest of the picture is visible - you should end up close to somewhere on the middle of the scale, just put it in the middle if you don't and you'll fix it in the next step.  Adjust contrast so that the top of the ramps are as bright as you care but not blooming.

Now adjust the cut-off/bias controls for each color (red, green, blue - these controls are usually on the neck card) so that the again the bottom 10-15% of the corresponding color ramp is fully black.  Then adjust the gain/drive controls for each color so that the top end of the corresponding color ramp looks about the same brightness as the others and the white ramp looks "white" to you (you can bust out a color temp reference, if you want to).  You may need to iterate back and forth some between the cut-off and gain settings to make both ends work out.   In particular, based on your problem description, your red cut-off is probably way too high and will need to be turned down in this step.

You should generally never need to adjust the screen control on the flyback again after this step unless the monitor exhibits extreme aging.

You should be set up at this point - you can adjust brightness/contrast to your preference, but they are pretty close to the "correct" setting.

[noahstauff]

I was checking some stuff out on the back of the monitor, and I un soldered the red transistor and the problem persisted. I then checked for shorts on the neck of the tube G1 is shorted to heater. There is lots of stuff about heater to cathode shorts but none on this. What should I do? Do I have to get a new monitor or is there some type of repair that will work? I will try to do as reccomended above but I don't think it will help.

Thanks,
Noah

[MonMotha]

Ah, well, that'll cause problems.

You can probably fix that using the same technique frequently used to fix other shorts to heater: isolate the heater.  A common trick is to wind a few turns of wire around the flyback (I don't remember the magic number 3 or 4, IIRC) and hooking that up to the tube heater (after disconnecting the original heater supply).

[noahstauff]

I isolated the heater and although th screen is bright enough to be used now, it did not fix the problem. Now I have ok brightness with red bleed through. The brightness is still pink however the retrace lines are now smaller and closer together. Even with red drive and cutoff all the way down it still has way to much red as indicated in a monitor test screen. Is my monitor on its last legs? Any ideas?

Thanks,

Noah

[epicfatigue]

Hey i may be way off,

But i had this exact problem on a k7000 WG.

Turn the brightness down on your FLYBACK then turn up the brightness on your remote board or pot located on the board itself.

Apparently you get these lines when the voltage is way to high.

Give it a try!

[MonMotha]

Yes, your screen (G2) control on the flyback may be too high.  I dunno why, but they often get cranked up when people want things "brighter" even though it's actually a rather coarse control to use for that purpose.

Otherwise you may have another tube fault (I'm guessing not a drive fault since you said the problem persisted with the drive transistor removed).  How did you determine you had that G1/H short?  I take it you've got a tube tester?

[noahstauff]

I do not have a tube tester, however I tested the neck if the tube with my multimeter and G1 has continuity with the heater pins. The problem with the flyback outputting pink is that I can adjust everything, but red is always too high. I have red drive and cutoff at the lowest possible settings. I don't really know what to do now. I have brightness on the remote board up all the way, and I adjusted the flyback like MonMotha suggested. I wrapped the wire around the ferrite core 2 and a half times, and this improved the screen a lot. Does this mean that my monitor's guns are weak? I could take pics of the improvement upon request.

Thanks for all the help,
Noah

[MonMotha]

Do you still get a red screen with the red drive transistor removed/lifted now that you've isolated the heater?

[noahstauff]

*Update* I turned on the machine just now, and now the brightness is blueish when turned all the way up. There seems to be almost no red in the picture, orange appears green. But in a monitor test program red is still full blast with the cut off and drive at minimum, howerver it is very dim. If I adjust it I just get red bleed through, and a very tiny bit of red to show up in the picture. The colors are really wierd now. I will try removing the red transistor again as you said, but i'm not sure what it will do at this point. I re-adjusted the monitor according to your earlier steps, but the picture still looks funky.

Thanks again,
Noah

P.s. I'll try to take more pics tomorrow.