Video impedance selector

[gamezer0]

Hello all,

I recently purchased an Astro City and an Atomiswave. Both of them have a switch on the remote board of the monitor to select proper “video impedance” but I have really no idea what that means and what the right value should be. I have tried both values with a couple boards and it does affect the brightness of the image… but not sure it has any side effects?

Any help appreciated.

 

[nem]

If you're using regular jamma boards, you want it on 1 Kohm.

Out of interest, what monitor chassis do you have in your cabs?

 

[hatmoose]

Consumer gear is normally .7 volts point to point and is terminated at 75ohm
Arcade hardware is normaly 4-5ish volts point to point and is terminated at 1kohm

Your monitor chassis is interesting in that it looks like it can handle both - i've never seen that before.

Anyhoo - as @nem has already said, for Jamma boards you'll want to set this to 1khom
If you were intending to put a console or a PC into the cabinet you could set this to 75ohm and the picture would look much nicer

 

[nem]

The exception to the arcade hardware rule is most things that have DE15 / "VGA" connectors on them. So an Atomiswave, a Naomi or a Tekken 3 will output 0.7vpp video from the DE15 connector. On the Namco System 2X6 video impedance can be set with a dipswitch.

 

[_rm_]

The Rodotron 666-A chassis has the same switch, but i've never seen that before on an Astro. Maybe someone replaced original chassis?

Only the OP can clarify

 

[gamezer0]

Thanks for the answers. Is there any harm in using the wrong impedance? Would a MiSTer be 75 or 1K?

The chassis are Nanao MS8 on the Astro (which was fully restored, so could be the monitor came from another donor), and a Wei-ya on the Atomiswave (yeah, with VGA) I don’t have the exact models but I can check later.

 

[_rm_]

Thanks for the answers. Is there any harm in using the wrong impedance? Would a MiSTer be 75 or 1K?

The chassis are Nanao MS8 on the Astro (which was fully restored, so could be the monitor came from another donor), and a Wei-ya on the Atomiswave (yeah, with VGA) I don’t have the exact models but I can check later.

Yup, Rodotron 666 and some Wei-ya models are very similar.

If you mess up the impedance you will either get a super bright or super dimm image and the color will also be off. You just change it on the fly for the correct impedance (with the chassis running, no problem) and everything will be fine.

 

[nem]

MS8s don't have impedance switches. There's a switch on the remote (SS.SW), but it's for "enhancing image quality" (it's a load of shit).