JAMMA to XRGB?

[brad c.]

Any ideas how to create a cable to go from JAMMA to an XRGB upscan converter?   I've seen some talk of this here, but has anyone done this?  Apparently, the input on the XRGB is a "Japanese RGB" 21 pin connector.  

http://www.gamesx.com/avpinouts/rgb21pinj.htm

Thanks.

[b3atmania]

Note, although similair in appearance, the Japanese 21-pin RGB multi AV connector has a different pinout from the European SCART plug!

Things to consider when doing signal conversion from JAMMA to Japanese 21-pin RGB:

• Unless you are absolutely sure the connected game output 0.7V(tt) level RGB signals, you would need to bring down the RGB signals to 0.7V(tt). Many arcade boards output RGB at 1..4V(tt). This will damage the XRGB as it is made for 0.7V(tt)
• The 21-pin connector on the XRGB accepts composite sync only. Some arcade boards output this, but most output horizontal and vertical sync seperately. You can combine H- and V-sync using this circuit. You may hear people say you can just wire the H- and V-sync together. Do not do this, as it is not the proper way to make a composite sync and will likely damage the XRGB.
  
• The XRGB can accept 15kHz Hsync only. If you arcade game outputs at 25kHz or higher, it won't work. It might even damage the XRGB.
• The XRGB was designed for 60Hz Vsync. It probably has some margin to go lower like 57Hz and 54Hz.
• If you also want to input sound via the 21-pin connector you again need to take care with amplified signals. Some arcade boards output sound amplified and will possible damage the XRGB. Non-amplified should be fine though.

As you can see, much depends on the arcade PCB that is being used. It's not an easy setup to work with if you change games often that use different signal levels. You would also need to check signal levels for every game you purchase. Unless you already bought the XRGB, I would recommend getting a good multisync monitor and save yourself the hassle.

[brad c.]

Thanks for the reply.   I was looking at the XRGB because my monitor is a 27" SVGA monitor made by NetTV (http://www.net-tv.net/), and of course does not support 15kHz.  It looks like it would be a lot of work to hook up the XRGB, so I will probably just go for a RGB to NTSC converter and use the s-video input of my monitor.  

Thanks for the info.   I'm glad somebody knows this stuff