Brightness problem with Valvo VCC93 arcade monitor

[guwu]

Hi,

I just finished converting a german TV Ideal Twinline cabinet into a MAME cabinet using Ultimarc's ArcadeVGA and the built-in Valvo VCC93 20" arcade monitor.

Everything works fine except for one problem: the more white there is in the picture the darker it gets.

Example: at the start of NeoGeo games there is a white screen whit the NeoGeo logo in it. During this the image gets a lot darker than usual, the white is more of a grey.

Another example: when I'm on the WindowsXP desktop and I maximize a explorer window which has a white background the image gets a lot darker.

I also noticed that if there is a lot of blue in the image (sky in "Out Run") the picture gets reddish.

Any suggestions for what I could do?

Thanks in advance!

[Ken Layton]

I've never heard of that brand of monitor.

[mattv]

Your arcadevga only outputs a 1 volt signal. Some arcade monitors are just fine with this 1 volt signal but many monitors expect a 4 volt signal like they would get if connected to a proper arcad game board.

I suspect that your monitor really wants a 4 volt signal, it will still display something with the 1 volt comming from the arcade VGA but by the sounds of things it is a little dim.

Your first step in fixing this problem is to convert your 1 volt arcade VGA signal into a 4 volt one.
to do this you will need either an ultimarc video amplifier which is designed for just this purpose
http://www.ultimarc.com/vidamp.html

Or alternitively a jpac interface which has a lot of other functionality and a video amp built in.
http://www.ultimarc.com/jpac.html
(don'y get the jpac lite, it's crap)

With a bit of luck that will fix your brightness and white weirdness problems. If not it's time for a new monitor.

[menace]

Hate to ask the obviuos but have you don a cap kit?  This often solves discoloration problems--As for dimness I agree with the above.

[guwu]

@mattv

Thanks, will try to get my hands on a video amp. No J-Pac needed as I'm using a USB2Jamma for the controlls.

[darklegion]

I believe that for some/all? monitors if the brightness level of white is higher than the monitors limit  it will try and drop the brightness of the rest of the screen in response.This may be what is happening here,in fact it could be that the signal is stronger than what the monitor wants,I.E it is probably expecting 0.7v p-p and the 1v is slightly overdriving it.Try setting it to 4-5V and run it through a video amp ,I believe most arcade  monitors have the option to switch between the 2 voltage settings.This is just a guess btw,it could be any number of things and I don't claim to be an expert on this.Worth a try in any case