RGB to HD15

[Arm123]

How hard is it to hook up an arcade PCB or Jamma board to a PC (HD15) monitor ?

I know that its quit simple to make the RGB connections, but what about the v / h sync of the boards ?

I just want to do this so its easier on me when test out some of these arcade boards that come in.

A link would be helpful.

Thanks

[gokun]

pins 13 and 14 on the vga side are your h and v sync. there are several grounds but I usually just attach them all through pin 10 with bridges(I'm an idiot though, so bare that in mind)...hope that helps

[Arm123]

thanks for the reply.

So i can just direct connect them ?..  Why did i think i needed some kind of circuit to convert something ?   stupid me. 

[MonMotha]

JAMMA sync is at TTL levels, which is what PC monitors expect, so you can just connect the sync straight through, yes.  If you only have composite sync available, place it on the horizontal line - this is the convention in the PC world, rather that placing it on both lines.

You can usually get by only using pin 4 for ground, but sometimes you'll have to tie them all together.

As for the video, be aware that PC monitors expect 0.7V peak video levels, while arcade boards often put out significantly larger signals (in the 3.3-5V range).  This will cause excessive contrast (likely blooming) on your monitor.  If this turns out to be a problem, it can be fixed with a single resistor to form a voltage divider with the monitor's internal 75 ohm termination.

Also, be aware that most arcade boards output standard res (15kHz horizontal scan rate) video.  Most PC monitors are not capable of displaying this (only going down to VGA, which is 480p, which is 31kHz horizontal).  Hooking it up won't cause damage, but it also likely won't work.

[Zebidee]

Check here for recent discussion of this very topic of putting resistors on video signals in JAMMA context:

http://forum.arcadecontrols.com/index.php?topic=71776.msg743221#msg743221

[Arm123]

wow...  fantastic info guys !

I will try the above method, to tie all GND to pin4 and see how she looks on my Dell 24" LCD 

Its just for quick testing of PCB / Jamma boards as they come past my desk.

thanks again.

[MonMotha]

My guess is a giant colored box containing the text "Cannot display this input signal", or something to that effect.

[Arm123]

My guess is a giant colored box containing the text "Cannot display this input signal", or something to that effect.

You are correct sir !  lol

It did end up working work on my Panny-8uk thought.

[gokun]

The main problem you're going to encounter, most likely, is gonna be frequency...basically, it's going to depend on the board you're testing and the signal it puts out(15K,etc) in conjunction with the modes your monitor supports....speaking personally, I have a lot of 15K boards and none of my LCD monitors support that mode for whatever reason...but I have an old 21" crt that does. Go figure. Anyway, what it boils down to is that if your monitor doesn't support the signal you get an out of range msg, otherwise it will generally work. But chances are a really new monitor won't support 15K mode(although most of them support 31K and a good number support 24K as well). So I guess what I'm getting at is it might be more trouble than it's worth if you're going to be testing old pcbs that run in standard res. BTW in case you didn't notice I kinda suck at explaining things so let me know if anything doesn't make sense.