scart RGB to arcade monitor what about impedance?

[truffelzwijn]

I am currently building an xbox arcade cabinet and i want to hook up the xbox to the RGB input of the monitor.

The monitor is a Hantarex MTC9110 (http://www.vernimark.com/arcade/manuali/monitor/mon_rc_mtc9110.pdf)

and the data file says:

Video input signals
RGB positive going with an input impedance of 2.2 kOhm. Input sensitivity from 1 to 5 V

Sync. Signals
Horizontal and vertical, positive or negative, composite or separate. Input impedance 2.2 kOhm. Input level between 1.5 and 5 V p.p.


Now i'm reading up on SCART specifications and i find this.

for all RGB channels
0.7V pk-pk +/- 2dB, 75 ohm input and output impedance

for composite video
1V pk-pk including sync, +/- 2dB, 75 ohm output impedance

Now i know very little about electronics, but it seems like these are not compatible with each other. Would i need some kind of resistors or amplifiers or will it work anyway  

Now i'm planning to use a L1881 sync splitter circuit for the sync signal.
But i'm not sure wether i can hook up the scart ouput directly to the monitor. Is there any danger in trying this?

Oh, here a pic of the cabinet:  

[tom61]

You should be able to hook up the SCART to the monitor just fine. You might or might not need an LM1881 circuit, try it without first, if it doesn't work, then order teh parts and build the circuit.

[truffelzwijn]

Thanks i will just do that.

One more question: i just opened up the scart bus on the cable and i find that there are 100uF 10V capacitors soldered on the R G and B leads. What are these for? Should i leave them or remove them?

[MameFan]

1) Arcade video monitors require a signal between 1 volt and 5 volts to drive each color gun.

2) Computers put out .7 volt MAX per each RGB wire.

(As per your stats above you found out).

Therefore if you attempt to drive an arcade monitor with a computer video card you will at most, have a very very dark picture with no contrast because not enough voltage will be making it to the monitor.

You will need to buy/make an amplifier for each line in order for it to work.

As far as the Sync goes.. as the previous poster stated, you'd be surprised. Often you do not have to split a composite sync signal, just connect the same cable to both the HSync and VSync pins on the monitor and you're good to go.  Most monitors have the ability to filter out only the part of the signal they need to use for each part of the circuit.  Many video game boards only output composite sync and yet work with separate sync monitors.

You may however, again, need to amplify the sync signal in order to work correctly.


I have done the exact opposite.. I'm using a 13" Commodore (Philips made) monitor as a test monitor for my boards.  It expected the low voltage input and therefore I have to put some variable resistors on each RGB line in order to bring the intensity of the signal from 5 volts down to .75 volts, otherwise the monitor is washed out with color.   Also I have to bring down the sync line because otherwise I get bad flagging on the top of the screen and other image impurities without one.

Good luck, let us know how it goes.

[truffelzwijn]

Thank you very much  

I tried today and i found the following.

The composite video is indeed good enough for the monitor to sync on BUT as you predicted the RGB signals are too weak. The picture is sharp but way too dark.

So, i need an RGB amplifier, does anyone have a scheme for one?(easy to build i'm no elektrotechnician )

[tom61]

Did you leave the caps on? You need to. Have you tried just turning up the brightness?

[truffelzwijn]

Yes i left the capacitors on and turned brightness up high (and the amplifiers for the RGB on the tube)....still a dark picture.....

I guess i really need that signal amplifier but i can not find a scheme for a suitable one.....Anyone?

[Cave]

What about the amp at ultimarc.com, this is mainly for vga cards but i don't see why it wouldn't work.

[Amra]

You might just buy a Scan Do Pro, will solve your problem the fastest.  That is... If you can afford it

[truffelzwijn]

Thanks or your replies...

Now I am pretty confused, i checked out the Extron super emotia and the Scan Do Pro but these (as far as i can tell) do not even amplify RGB signals.....they are bot VGA to PAL convertor.....

I have RGB signals (0.7 V) that need to be amplified to 1-5V....Surely it must be possible to amplify those without the need for very expensive equipment.

What about the circuits that are listed here?

http://www.epanorama.net/links/videochips.html#amplifier

Is there one that i can use for my purpose?

I really don't want to spend 100 euro or something that i can probably solder myself for a lot less money.

[tom61]

The video amp from Ultimarc is $15(it's not just for VGA, it just includes cables for that purpose): http://www.ultimarc.com/vidamp.html

Ordering page:
http://www.ultimarc.com/orderd.html

Ignore Snaaake and Amra, they must've skimmed too fast and must've thought you meant for interfacing a PC, not an X-Box

[truffelzwijn]

Thanks heaps that's EXACTLY what i need

I checked out that site yesterday but i couldn't find the video amplifier (it's only listed on the 'order' page).

I'll order one today, hopefully it will arrive soon. If i get everything up and running i'll report back here  

[AndyWarne]

The Hantarex monitors generally have a switch which is set either to 1 volt video or 5 volt.
Are you sure you have switched it to 1 volt?

Andy

[truffelzwijn]

There's nothing mentioned in the service manual about such a switch. I've seen the monitor run with a jamma board and looked very good.

I'll just wait for the amplifier to arrive and use.

What should i do with the sync signal. The monitor works with the composite video connected to the jamma connector. Should the composite video also go through the amplifier or bypass it?

Thanks

[truffelzwijn]

This is INCRDEIBLE

I received my amplifier today...that's only THREE days after ordering. Big thumbs up for www.ultimarc.com

As soon as i have time i will install it. What should i do with the capacitors on the amplifier side of the cable. Take them off, leave them on, attach them to the output side of the amp. Also, what should i do with the sync signal. Pass it through or loop it around the amp?

Thank you very much



-edit-

I just tried hooking the amp up but something is not right. I turn on the xbox then the monitor. I get a picture (colors) but within a few seconds the picture turns so bright that after 10 seconds it's completely white...What am i doing wrong?

Also i am not quite sure how to how hook it up. Should i leave the capacitors on?

Here's what i did:

R (xbox) -> R (input)
G (xbox) -> G (input)
B (xbox) -> B (input)
composite video (xbox) -> sync (input)
grounds (xbox R&G&B and comp. ground) (ground power supply) (ground monitor)-> ground (input)
+5V (power supply) -> +5V input

The outputs go to the R G B and sync of the monitor

Is this the correct way?

[Anonymously]

I'm trying to do the same thing and I got it actually to work, but I encounter some problem maybe we can help each other with this.  Here is the post on what the problem is.
http://www.arcadecontrols.org/yabbse/index.php?board=4;action=display;threadid=5869