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Positive Sync VS Negative Sync, RGB transistors buffers?


vanwatson

Question

Some Arcade Logic boards output a Positive composite sync , but most arcade logic boards output a negative composite sync. Does using a Positive Sync signal change the display or what is the differences? is the image better when using positive sync

 

Some monitors are Vertical Raster Scan and others are Horizontal Raster Scan, what is the difference?

 

The Anode cap on the monitor is mounted on the Right side for monitors with a vertical raster scan?

The Anode cap on the monitor is mounted on the Top side of the monitors with a horizontal raster scan?

 

Does all Arcade monitors have these RGB resistors and RGB output transistors? these RGB transistors go direct to the Monitor

 

The Red channel has a resistor and a transistor that gets connected to the monitor display

The Green channel has a resistor and a transistor that gets connected to the monitor display

The Blue channel has a resistor and a transistor that gets connected to the monitor display

 

They call this circuit a discrete ADC convert

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This is in arcade manuals

 

Switch Negative Sync To Positive Sync

7404 or 74LS04 chip

Pin#1 from Logic Board Negative composite sync

Pin#2 is output to monitor positive composite sync

 

But why would I want to switch the sync polarity? does it give a better picture or display advantage?

 

Which games use Positive sync and which games use negative sync

 

Is Positive sync ment for certain graphic games or something?

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I'm no expert or old-school technician, so I'm happy to be corrected on this, but I'll throw in some info from my understandings.

 

Firstly, negative vs positive sync. I think to be honest this isn't something that has an impact to the end result, but more a side-effect of a lack of standards. Back when these were made, people sat in workshops/engineering without the internet, without massive collaboration, and very expensive long distance communication. Each place did their own thing. Turns out there's 2 ways of sending the sync from the board to the screen. SOme guys did it one way, some guys did it another. All it really means is, the monitor and game board have to match. You use an adapter/converter of various forms when you want to use game board A with a monitor B, and they take opposite types of sync. There are many monitors that can auto-detect and take either sync without an adapter.

 

Horizontal vs Raster is actually quite simple. It describes the physical orientation of the monitor. This is why you have the observation of the anode cap in different locations. The monitor is literally rotated. these monitors aren't square, they are 4:3, which means longer on one side than the other. Some games are designed for a 'wide' screen, and some are designed for a 'tall' screen.

 

Think for example, 1942, which is a game that works up/down the screen a lot, this is a vertical game. However a game like Street Fighter mainly works left-right, so is a horizontal game. The same monitor is used for both, just physically rotated. Most generic cabs actually have a mounting system that allows for someone to physically rotate the monitor (while in a service shop or similar, not something the user does!) There are actually mame cabinets that can have rotated screens however, even some with motors to do it! This is a mame thing, tho, not an arcade thing. Typically, you would only rotate a screen if you changed out the game board for one of the other direction. Games were designed for the orientation that best suited their gameplay. So in short, a monitor is only "raster scan", horizontal or vertical is simply implying the manner in which it is mounted.

 

I'm not sure what you mean in regards to transistors in this context? I would assume typically there would be some form of transistors for protection to the boards themselves, in case +5 got put into it, for example.

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