What monitor adjustment does what?

[channelmaniac]

Many games were made with Wells garnder monitors with a remote pot PCB which was located under the control panel in front of the monitor.  Some may have been moved or mounted to the side of the cabinet.  Older monitors don't have a remote pot board and all the adjustments would be found on the back of the main monitor board facing the back door of the game.  BE careful not to hap hazardly adjust controls labeled Horiz Freq. or Horizontal Hold as they can kill parts on the board if taken way out of normal range.

What does what?? :

Horizontal Hold or frequency: Adjusts the frequency that the monitor runs at.  Can cure scrambled picture (diagonal moving lines).

Vertical Hold or Frequency: Adjust the "rolling" of the picture (top to bottom / bottom to top)*

Horizontal Size or width or Amp (amplitude): Size of picture right to left*

Vertical Size or Amp.: Size of Picture top to bottom

Brightness: Overall brightness of all the images on the screen

Contrast: the Difference between what should be white and what should be black.  Can improve clarity or smear image.

50/60 (cycle adj): designed to make monitor compatible with multiple markets but has a tendency to correct vertical "Fold over" at the bottom of many Wells Gardner 7000 series monitors.  Usually small trim pot located just behind Horiz Hold.

Black Level: kind of a combination of Brightness and Contrast but mostly performs like Contrast.  Should be adjusted by removing video signal, and adjusting to just the point where the gray screen turns black.  Re-connect video signal and adjust other controls.

On Flyback Transformer:

Screen Level: (usually the bottom control) Adjust overall screen level to entire picture tube - can wash out picture or bring up brightness if too dark.  Overdriving can also smear image or make image fuzzy.

Focus: (Usually the top control - some monitors have two focus controls) Adjust the fuzzyness of the image by smearing it left to right or up to down.  Proper adjustment is where the image doesn't smear either way or the least of both ways.  Turn it while watching and you will see what I mean. If two focus controls, one will do horizontal focus, other vertical.  One may have no effect if not dual focus tube.

* Horizontal and Vertical refer to a normal picture tube placed like you would view a normal TV with the long dimension right to left.  Many older video games have their screens mounted "Vertically" and the controls will have the oposite effect than described above.

You should avoid adjusting any control on the Neck PCB ( the small board that plugs into the end of the CRT tube)  These are usually Red, Green, and Blue Drive and Cutoff controls and are typically set to match the CRT color levels.  IF you find the RGB gain or level controls on the main monitor board, you can safely adjust them to raise or lower the amount of said color.

Keep in mind many older CRTs (picture tubes) are now "bad" any may no longer be able to produce a particular color (R, G, or B) or are driving one of those colors too much or all the time.  No neck PCB adjustment can make one of these failed tubes look proper.  These types of tubes need to be rejuvinated by a qualified TV Repair man.  This was typically a $95 service at a TV shop.  Rejuvination, however, can totally destroy a tube but then, it is already bad to beging with if you were to try to rejuvinate it.

CJ