H-sync and V-sync for arcade monitors

[vanwatson]

What is the H-sync rate and V-sync rate for 70's and 80's arcade monitors?

[lilshawn]

probably/maybe/possibly 15k.

vsync is usually 60hz/50hz depending where you live and may even vary from one game to another (some used custom resolutions and oddball signals to get you to buy replacement parts from them.)

standard res: 15k

medium res: 25k

high res: 31k and up

[vanwatson]

vsync is usually 60hz/50hz depending where you live

Black and white TV's vsync has at 60hz also?

So the H-sync is at 15Khz?

What is the IC chips name that does the V-sync , H-sync, Blanking signals? is it called a sync separator chip or is it called something else for arcade games?

This Sync separator chips outputs the V-sync at 60hz and the H-sync at 15Khz?

[lilshawn]

some arcade monitors use separate horizontal and vertical sync signals, others use a H+V mixed sync called composite sync. these monitors would use a sync separator IC to have separate horizontal and vertical sync.

while still others can accept either one - a horizontal or vertical sync and use various trickery to emulate the missing sync signal for the rest of the scan system

[vanwatson]

So you're saying that some arcade games have only vertical sync or only horizontal sync?

some arcade monitors use separate horizontal and vertical sync signals, others use a H+V mixed sync called composite sync.

Is it the EPROM chips, PPU picture processing Unit OR the CPU that is outputting the video signals , H-sync, V-sync?

Or what does the EPROM chips have on them?

The PPU chip does the RGB coloring , hues, mixing of colors?

[ed12]

it is all in the logic of the board
some board's combine horz/vert sync toghter,some run sep horz/vert sync's
it is all up to the game and it's board designeer

ed

[vanwatson]

Mostly the Composite syncs are Negative sync , but other arcade games composite are positive sync. What is the difference is displaying or they both display the same?

How do you convert a Negative composite sync to a Positive composite sync?

It is the CPU or ROM that is outputting the Composite Sync signal?

[vanwatson]

The H-sync is at 15Khz , I think it has a Horizontal oscillator circuit or crystal that sets up the 15khz
The V-sync is at 60hz, this has a vertical oscillator circuit or crystal set up at 60hz?

The Oscillator circuit or crystals are on the deflection monitor pcd board?

[ed12]

90% of monitor's have pervision's for both + or - sync

>How do you convert a Negative composite sync to a Positive composite sync?<

if u look at a g07 electrohome
or any wg u will see it clearly listed
+/- sync as seperate input's

ed

[vanwatson]

Yes all monitors have in the sync polarity inputs

You can convert the negative V-sync and negative H-sync to a Positive V & H Sync from the logic board using an IC chip

WG is Positive Sync
Electrohome is Negative Sync

The Logic board mostly outputs only negative syncs , you have to convert it to a positive sync before going to the monitor

[ed12]

if u look up a schmeatic for a g07/08 and or a wg
u will find a set of tranistors that do just that >invert _or or _nor<

ed

[vanwatson]

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 left 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?

 

[ed12]

tube oerntation to the horz plane

ed

[lilshawn]

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 left 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?

anode is usually on the right for a vertical orientation, but again, not always.

[vanwatson]

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

[lilshawn]

again, just so you are forced to purchase replacement parts from the manufacturer of the game.

[vanwatson]

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?

[lilshawn]

back in the day, some manufactures got "smart" and decided to reverse the polarity of the sync signals, that way, when and if your monitor broke down, you'd have to purchase a replacement from the game maker (atari, nintendo or whomever) Because a "standard" negative sync monitor wouldn't work with your game board, you were forced to have them replace the unit. Hackers with the vendors would often just run the sync signal to an inverter circuit (IE the 74LS04) to change the signal around and make it negative again... later monitor manufactures got wise to the shenanigans of the game companies and started making monitors that could take either polarity.

there is no advantage to one or the other, it's just simply electrical trickery to get vendors to purchase product from the maker because of the proprietary nature of the video sync signal.

nintendo did the same with their RGB signals on a few games (using an inverted signal) same thing... just a proprietary signal to get vendors in the corner to buy product from them.

/historylesson