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Sp33dFr34k

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Currently I have the VGA connector wired straight to the connector of the Nanao MS9 monitor in my NAC. Because a Naomi has standard VGA output, meaning less than 1v output on the RGB lines, the picture looks dull and not very vibrant.

So I thought I had a brilliant idea by amplifying the Naomi video output with the help of an Ultimarc Monitor Video Amplifier.

I wired how it how it's supposed to be wired. And I split the H/V sync, image works beautiful like it should...

For about a few seconds, the screen is being oversaturated very slowly, only to be going to very very dim, until you don't see jack shit anymore 8|

So the voltage on the RGB lines are starting at about 3.7v, then going up to abou 4.2v-4.3v and the image is being blacked out.

I literally have no clue what is happening here. The 5v pad on the Ultimarc PCB is getting close to 5v, so the Naomi is actually delivering the 5v via pin 9 of the VGA connector.

Can anybody chime in what's happening here? ?(
 
I have one of these installed on my Revenge from Mars Pinball (a VERY common mod on those games).

I had issues similar to this and it ended up being too much resistance on the 5V wire. I ended up swapping to a different VGA cable that had higher gauge wires, and I think I also added a jumper wire on the video card to ensure that there was a strong 5V signal on the pin too.

I think normal people would just run a separate 5V harness to the adapter. I'd recommend running a nice 20 awg or so 5V and GND to the adapter from your PSU as a test just to rule that out.

Although, I'm curious why you're using a VGA connection on your NAC rather than just using one of the JAMMA converters which should have video amplification built in already.
 
Although, I'm curious why you're using a VGA connection on your NAC rather than just using one of the JAMMA converters which should have video amplification built in already.
This. How are you handling controls?
 
Thanks TS, I will try running a seperate 5v line to the amplifier and take out pin 9 from the VGA cable, see if that helps.

As for the questions how and why, I just wanted my NAC to be versatile so I basically prepped it for easy switching between jamma and JVS.

I handle the JVS power and sound via the NVS4000 PSU and for the controls I wired in a JVS IO in parallel to the jamma controls. Did this a long time again and it works perfectly. I just found the Capcom IO to be quite bulky and not very convenient.

Here are some old pics:

 
Okay so I wired 5v from the JVS IO header, same way I usually power my Raspberry Pi. Took an old VGA cable and yanked out pin 9 on both ends just to be sure. Same exact problem. Could it be I have a faulty amp here...?
 
Got this reply back from Ultimarc:

"This would indicate the amp is not suitable unfortunately. The issue would be the video output and input is AC coupled which causes a DC voltage to build up which swamps the video signal. The amp will only work with DC coupled video which is produced from standard game boards and video cards.


The dim video would likely be monitor adjustment, contrast, brightness or screen controls."

Not sure if there is a way around this, maybe you know something more about this @acblunden2?
 
The only thing I need done is to amplify the video output, that's it... :( I can wire another JVS IO in there, but I'd only use it for amplifying the VGA output, would be a shame. Surely there is a simpler way to achieve what I want?

I am not sure how to measure whether it's AC or DC coupled video the Naomi outputs?
 
I started this project, but the PCB is flawed. Simple fix though. Just don't know when I will get around to it. Supposed to be the same circuit as the one that Arthrimus built for the JAMAizer. It works off of 5volts coming off of VGA pin 9 and was designed for MAME. For NAOMI, you need to source 5v elsewhere as there is no Pin 9 on the NAOMI (I think).

You can build your own RGB amp too.
 
The Naomi does deliver 5v on pin 9 actually.

Thanks, I'll have a look into that.
 
Powering anything but an EDID EEPROM off of VGA pin 9 is sort of not what that pin is for, and it's usually current limited rather heavily. I doubt your issue is related to this, but it's worth noting that getting 5V elsewhere is a better idea. You may have experienced inline HDMI->VGA DACs and other peripherals that aren't terribly reliable, and this is often the cause.
 
Ultimarc's standalone video amp based off the same amp as the J-Pac uses Pin 9 off VGA. Users can also jumper 5v into the standalone Ultimarc video amp. For the J-Pac, he is pulling 5v off USB. If I ever get around to messing with that PCB again, will make it so you can pipe in 5v from elsewhere then. My PCB design know how is fledgling. What ap do you use for PCB design @Hatsune Mike?
 
I have a hard time believing that the NAOMI is AC coupled.
I was thinking about this, the NAOMI could be AC coupled 15khz. NAOMI shares much of its circuitry with a Dreamcast. 15khz out of a Dreamcast is AC coupled. So Ultimarc might be right.
I did try getting 5v elsewhere as well, same result unfortunately :(
Harvesting +5v off a Naomi is easy. Anyways, just build that RGB amp. Quick fix for you unique situation. Also, follow @Arthrimus diagram and you should be good to go.
 
Yeah I usually take it off the Naomi or JVS IO, they're both 4 pin JST-NH connectors which I have plenty in stock. But doesn't make a difference unfortunately.

I'll give @Arthrimus design a go... for the amp, is the THS 7375 the THS7375IPW or THS7375IPWR version, or should both work?
 
Tried the Raspberry Pi yesterday, running Lakka in 15khz and strangely the picture is very bright and vibrant compared to the Naomi... sent @Arthrimus a PM asking if he has a separate video amp PCB and if not, I'll just try whipping one up myself on a breadboard. It's only use would be the Naomi, so it's no prio really... just annoys me a bit it's never as easy as I think :P
 
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